Throughout our lives, certain archetypes shape our sense of self, the world, the road we’re on, and the goals we seek. Our idea of good and evil, male and female, leaders, parents, mentors, friends, and more are framed in the stories of the Bible. The picture’s not always pleasant, but it never fails to be instructive and is sometimes downright revelatory. Mirror, mirror on the wall: what’s the purpose of us all?

Topics of the Day:

Sunday, Day 1: “Introduction” and “Your Life as Revelatory Source. How did you get to be who you are? Your life is a sacred text read by all.

Monday, Day 2: “The Character of God” and “The Male/Female Thing” You and I meet God in sacramental and sacred encounters. But in Scripture, we meet the God who is one character among many in the remarkable story of faith. And our second topic — Gender is complicated. Adam and Eve were just the beginning of the conflict. Gender issues remain with us in secular and sacred realms.

Tuesday, Day 3: “Follow the Leader” and “The Parent Trap”

Leadership styles come and go. From biblical patriarchs and kings to modern-day presidents and celebrities, we follow the leaders we invent and choose. And our 2nd topic – The Ten Commandments bid us to honor our father and our mother. Jesus says we should hate our parents. Please explain!

Wednesday, Day 4:“The Guiding Light” & “You’ve Got a Friend” Elisha had Elijah. Timothy and Titus had Paul. Thank God for mentors: those significant folks along the way who show us how life works. Our second topic — It’s not good for us to be alone, as Genesis attests. Famous friendships help us explore the role of holy companioning.

Thursday, Day 5: “Who’s Your Devil?” and “What a Wonderful World” Everyone fears the Dark Side. Who’s the enemy, and where does it reside? And our second topic — The universe is beautiful. Earth is our home. The Bible and science agree it will come to an end one day. What’s our relationship to a fragile planet?

Friday, Day 6: “And the Purpose of It All Is” We’re born, we live, and we die. For most of us, that’s a pretty full plate of responsibilities. What should we do with this “one wild and precious life?”What qualities are we looking for in the aspirants at Saint-Sulpice? Parish Experience - Before an aspirant joins the Society, Sulpicians want to ensure that an aspirant has completed at least two years of parish work, which will have allowed him/her to develop a strong sense of belonging to the diocese and an attachment to the parish ministry. Indeed, they need priests who live and love their priesthood and who wish to assist the bishops in the service of seminarians and diocesan priests. Ability to work in a team - Sulpicians are looking for candidates who are able to work in a community environment and are able to work collegially on a mission in consultation with fellow priests as well as with lay people or religious. To know how to share one's faith through a life of prayer that nourishes a true enthusiasm for Christ and his Gospel, for the Church and the priesthood. The Apostolic Spirit who animated their founder, Jean-Jacques Olier, is the source of this sharing. Special gifts that open the way to a quality intellectual and professional preparation in several fields: spiritual accompaniment, teaching of philosophy or theology, pastoral animation. This presupposes the openness to learning of a constantly renewed Sulpician pedagogy. How can a priest become a Sulpician? Prerequisites - To be a diocesan priest incardinated in a diocese, to have completed at least two years of parish ministry in the diocese of origin and to be available for service in the Canadian Priests of St. Sulpice Province. Initial recognition - If a priest meets these prerequisites, he or she can contact the Sulpician Vocations Officer for his or her region (see list below). He will inform him about the regular meetings organized for the aspirants to the Society and he will be in charge of this first experience with Saint-Sulpice until the Provincial Council accepts him as a candidate. His participation in these meetings will give him sufficient information about the Company and the demands of Sulpician life. This priest will also be accompanied spiritually in discerning his possible Sulpician vocation. Candidature - After this time of discernment, with the support of the Sulpician Vocations Officer in his region, he asked his bishop for written authorization to make an experience in Saint-Sulpice. The aspirant then applies by contacting the provincial superior or the provincial delegate in writing. First experience in Saint-Sulpice - If formally accepted and admitted as a candidate, the Provincial Council becomes directly responsible for his experience with the Priests of Saint-Sulpice. He then took over his duties and gave him a first appointment to a team in the Canadian Province from the moment his bishop relieved him of his duties. Usually, this first experience in the Company lasts at least two years.The expression "art Saint-Sulpice" is misleading, because it encompasses very different periods and artists in the same name and in the same discredit, because it confuses art of reproduction and wide circulation with the search for an authentic sacred art which has been continuous for nearly two centuries.

 

In the proper sense, Sulpician art refers to the objects that are sold in the specialized shops that surround the church of the same name in Paris: industrial and economic art, of poor quality, where the mimicry and the fading of style reassure and somehow carry the seal of an official art, orthodox and without excess. Thus understood, Sulpician art is of all times and every effort to renew religious art naturally secretes its counterfeiting. The virgins and saints, with their white eyes and pale air, coming from Ary Scheffer and his raphaelism, the statues of the Virgin of Lourdes, poor translation of the mediocre model of the pious sculptor Cabuchet, the overly sensitive effigies of Thérèse de Lisieux or Saint Anthony of Padua, even the neo-byzantine works, pale reflection. In fact, the interest of Sulpician art is not only sociological; it is also, as in countertype, the revealing of the interest that religious art has never ceased to arouse, against all appearances. Holy Mirror! The creatures on the reverse will be merged in the reflected image but probably not in a laplacian way - just as concentric circles. If anyone has a magic mirrorWe first address the problem of simultaneous image segmentation and smoothing by approaching the paradigm from a curve evolution perspective. In particular, we let a set of deformable contours define the boundaries between regions in an image where we model the data via piecewise smooth functions

 

www.vallombrosa.org/the-holy-mirror-discovering-ourselves...

 

Origin of the Holy Mirrors!

Mirrors have been regarded as sacred at least since the Han Dynasty in China. Many of these mirrors and from the subsequent Wei dynasty have been found in Japan. They bore images of gods and sacred animals particularly the Chinese dragon (1,2) . They were very popular, and possibly later manufactured, in Japan. The bronze mirrors are found in great number in ancient (kofun period) burial mounds in Japan. In the biggest archeological find of 33 mirrors, the mirrors were placed surrounding the coffin such that their reflective surface faced the deceased. The Han mirrors were "magic" in that while they reflected they were also able to project an image usually of the deities and animals on the back and refered to as "light passing mirrors" (透明鑑） (Needham, 1965, p.xlic; Needham & Wang, 1977, pp. 96-97).This magic property is due to the their method of construction. When polishing the reflective face of the mirror, the patter on the back influences the pressure brought to bear on the reflective surface and change the extent to which it is concave. Muraoka also claims that Differences in the (slight) "inequality of curvature" (Ayrton & Perry, 1878, p 139; see also Thompson, 1897, and Needham & Wang, 1977, p96 for a diagram) of the mirror result in the mirror reflecting light bearing the pattern shown on the reverse. More recent research has elucidated the precise mathematical model describing the optics of these mirrors as a laplacian image (Berry, 2006), a type of spatial filter today used for edge detection and to blend two images together. It is not known whether the mirrors popular in ancient Japan were also able to project, but later during the Nara period mirrors were found to concel magic Buddhist images, and during the Edo period, concealed Christians (Kurishitan) concealed images of the cross or of the Holy Mary within their bronze "magic" mirrors. Mirrors in Japan contined to be made of brass, until the arrival of Western glass mirrors, and were "magic" in that they displayed the patter on their reverse when reflecting sunlight or other powerful light source (Thompson, 1897). Ayrton (Ayrton & Perry, 1878; Ayrton & Pollock, 1879) claims that in Japan mirror vendors were unaware of the "light passing" quality, and that there is no mention of this 'magical' quality known to Han Chinese in Japanese texts. Even a Japanese mirror maker was unaware of how to make magic mirrors though had inadvertently made one himself by extensive polishing a mirror with a design on its back (Ayrton & Perry, 1878, p135). Unlike the ancient Korean mirror top right (3), the ancient Han and Japanese mirrors were made to be rotated, displaying images in the four directions of the compas. The reason for the holes in the central "breast" (or nipple) is unclear but it is found to be pierced with a hole (of varying shape depending upon the manufacturer) from which the mirror was suspended by a rope. Bearing in mind that the images on the mirrors required that the mirrors be rotated, the central nodule might also have enabled the mirrors to be spun like a top. I am not sure why someone would want to spin a mirror but my son does (see the toy explained later). I would very much like to see what the reflected "magic" image becomes when spun. The creatures on the reverse will be merged in the reflected image but probably not in a laplacian way - just as concentric circles. If anyone has a magic mirror I would like them to try spinning it to see. Skipping the holy mirrors in shrines, mirror rice cakes, and the mirror held by the Japanese version of Saint Peter at the Pearly Gates, King Enma, which holds a record of ones life, and, jumping to the present day... Mirrors are popular in the transformational items used by Japanese superheros. The early 1970's Mirror Man transformed using a Shinto amulet infront of any mirror or reflecting surface. Shinkenja, a group of Super Sentai or Power Rangers, that transforms thanks to their ability to write and then spin Chinese characters in the air, also transforms with the aid of an Inro Maru (4) upon which is affixed a inscribed disk. When the disk is attactched to the mirror the super hero inside the mirror is displayed. Transformation (henshin) by means of a mirror is popular too among Japanese femail super heros notably Himitsu no Akko Chan (Secret Akko), who could change into many things that were displayed in her mirror, sailor moon, and OshareMajo (6). The female super heroes mirrors usually make noises rather than contain inscriptions. The latest greatest Kamen Rider OOO sometimes transforms by means of his Taja-Spina which spins three of his totem-badge "coins" inside a mirror (video). In this ancient tradition we see recurrence of the following themes 1) Mirrors being of great benefit to the bearer enabling him to transform. 2) Mirrors containing hidden deities 3) Mirrors being associated with symbols: iconic marks, and incantations. 4) Mirrors being made to be rotated or spun. Thanks to James Ewing for the Mirror Man (Mira-man) reference and to Tomomi Noguchi for the Ojamajo Doremi reference, and to Taku Shimonuri and my son Ray for getting me interested in Japanese superheros. Addendum One of My students (A Ms. Tanaka, and a book about the cute in Japan) pointed out that the Japanese are into round things, and it seems to me that this Japanese preference for the round may originate in the mirror. Anpanman and Doraemon and many "characters" have round faces The Japanese Flag features a circle representing the sun and the mirror Japanese coats of arms (kamon) Japanese holy mirrors are round "Mirror rice cakes", and many other kinds of rice cake, are round The Sumo ring is round Pictures of the floating world (Ukiyoe) often portray the sitter in a round background Japanese groups always have to end up by standing in a round The Japanese are fond of domes and have many of the biggest The Japanese are fond of seals (inkan), which are round Japanese groups just can't help standing in a round The taiko drum is round The mitsudomoe is round Mount Fuji is round But then there are probably round things in every culture?

Cast and polished bronze mirrors, made in China and Japan for several thousand years, exhibit a curious property [1–4], long regarded as magical. A pattern embossed on the back

is visible in the patch of light projected onto a screen from the reflecting face when this is illuminated by a small source, even though no trace of the pattern can be discerned

by direct visual inspection of the reflecting face. The pattern on the screen is not the result of the focusing responsible for conventional image formation, because its sharpness is independent of distance, and also because the magic mirrors are slightly convex. It was established long ago that the effect results from the deviation of rays by weak undulations on the reflecting surface, introduced during the manufacturing process and too weak to see directly, that reproduce the much stronger relief embossed on the back. Such ‘Makyoh imaging’ (from the Japanese for ‘wonder mirror’) has been applied to detect small asperities on nominally flat semiconductor surfaces [5–8]. My aim here is to draw attention (section 2) to a simple and beautiful fact, central to

the optics of magic mirrors, that has not been emphasized—either in the qualitative accounts or in an extensive geometrical-optics analysis : in the optical regime relevant to

magic mirrors, the image intensity is given, in terms of the height function h(r) of the relief.on the reflecting surface, by the Laplacian ∇2 h(r) (here r denotes position in the mirror plane: r = {x, y}). The Laplacian image predicts striking effects for patterns, such as those on magic mirrors, that consist of steps ; these predictions are supported by experiment

The detailed study of reflection from steps throws up an unresolved problem concerning the relation between the pattern embossed on the back and the relief on the reflecting surface. The Laplacian image is an approximation to geometrical optics, which is itself an approximation to physical optics. The appendix contains a discussion of the Laplacian image starting from the wave integral representing Fresnel diffraction from the mirror surface. Geometrical optics and the Laplacian image If we measure the height h(r) from the convex surface of the mirror (figure 3), assumed to

have radius of curvature R0, then the deviation of the surface undulations from a reference plane (figure 3) is η(r) = − r22R0+ h(r. The specularly reflected rays of geometrical optics are determined by the stationary value(s) of

the optical path length L from the source (distance H from the reference plane) to the position

R on the screen (distance D from the reference plane) via the point r on the mirror. This is L = (H − η(r))2 + r2 +(D − η(r

))2 + (R − r)2≈ H + D + (r, R), (2)where in the second line we have employed the paraxial approximation (all ray angles small), with (r, R) = r2 2H+(R − r)2 2D+ r2 R0− 2h(r). In applying the stationarity condition ∇r(r, R) = 0, it is convenient to define the magnification M, the reduced distance Z, and the ;demagnified observation position r referred to the mirror surface: M ≡ 1 +D H+2D R0, Z ≡ 2D M , r ≡ R M . We note an effect of the convexity that will be important later: as the source and screen distance increase, Z approaches the finite asymptotic value R0. With these variables, the position r

(r,Z), on the mirror, of rays reaching the screen position r, is the solution of r = r − Z∇h(r). The focusing and defocusing responsible for the varying light intensity at r involves the

Jacobian determinant of the transformation from r to r, giving,after a short calculation,Igeom(r,Z) = constant × ∂x ∂x

∂y ∂y − ∂x ∂y ∂y ∂x−1 r→r (r,Z)= 1 − Z∇2 h(r) + Z2

∂h(r) ∂x2 ∂h(r) ∂y2 − ∂h(r) ∂x ∂y2−1r→r(r,Z), ().where the result has been normalized to Igeom = 1 for the convex mirror without surface relief (i.e. h(r) = 0). So far, this is standard geometrical optics. In general, more than one ray can reach r—that is, can have several solutions r—and the boundaries of regions reached by different numbers of rays are caustics. In magic mirrors, however, we are concerned with a

limiting regime satisfying Z Rmin 1, where Rmin is the smallest radius of curvature of the surface irregularities. Then there is only one ray, simplifies to r ≈ r, (9) and the intensity simplifies to ILaplacian(r,Z) = 1 + Z∇2 h(r). This is the Laplacian image. Changing Z affects only the contrast of the image and not its form, so explains why the sharpness of the image is independent of screen position, provided holds. The intensity is a linear function of the surface irregularities h, which

is not the case in general geometrical optics (i.e. when is violated), where, as has been emphasized the relation is nonlinear. And, as already noted, for a distant source and

screen Z approaches the value R0, implying that (8) holds for any distance of the screen if R0 Rmin, that is, provided the irregularities are sufficiently gentle or the mirror is sufficiently

convex. Alternatively stated, the convexity of the mirror can compensate any concavity of the irregularity h, in which case there are no caustics for any screen position.The theory based on the Laplacian image accords well with observation, at least for the mirror studied here. The key insight is that the image of a step is neither a dark line nor a bright line,

as sometimes reported , but is bright on one side and dark on the other. It is possible that there are different types of magic mirror, where for example the relief is etched directly onto

the reflecting surface and protected by a transparent film , but these do not seem to be common. Sometimes, the pattern reflected onto a screen is different from that on the back, but

this is probably a trick, achieved by attaching a second layer of bronze, differently embossed, to the back of the mirror.

Pre-focal ray concentrations leading to Laplacian images are familiar in other contexts, though they are not always recognized as such. An example based on refraction occurs in old windows, where a combination of age and poor manufacture has distorted the glass. The distortion is not evident in views seen through the window when standing close to it. However,when woken by the low morning sun shining through a gap in the curtains onto an opposite

wall, one often sees the distortions magnified as a pattern of irregular bright and dark lines. If the equivalent of is satisfied, that is if the distortions and propagation distance are not too

large, the intensity is the Laplacian image of the window surface. (When the condition is not satisfied, the distortions can generate caustics.) Only the optics of the mirror has been studied here. The manner in which the pattern embossed on the back gets reproduced on the front has not been considered. Referring to ,this involves the sign of the coefficient a in the relation between hback and h. There have been several speculations about the formation of the relief. One is that the relief is generated while the mirror is cooling, by unequal contraction of the thick and thin parts of the pattern ; it is not clear what sign of a this leads to. Another is that cooling generates stresses, and that during vigorous grinding and polishing the thin parts yield more than the thick parts, leading to the thick parts being worn down more; this leads to a 0: bright (dark) lines on the image, indicating low (high) sides of the steps on the reflecting face, are associated with the low (high) sides of the

steps on the back , not the reverse (figure 7(b)). This suggests two avenues for further research. First, the sign of a should be determined by direct measurement of the profile of the reflecting surface; I predict a > 0. Second, whatever the result, the mechanism should be investigated by which the process of manufacture reproduces onto the reflecting surface the

pattern on the back. The fact that h0 = 378 nm is smaller than the wavelengths in visible light does not imply that the Laplacian image is the small-κ limit of (A.3), namely the perturbation limit corresponding to infinitely weak relief. Indeed it is not: the perturbation limit, obtained by

expanding the exponential in (A.3) and evaluating the integral over τ , with a renormalized denominator to incorporate the known limit I = 1 for ξ = ±∞, isψpert(ξ , ζ, κ) = 1 − iκ erf(ξ/√1+iζ /κ)

√ 1 + κ2 . For the gentlest steps, this predicts low-contrast oscillatory images, very different from the Laplacian images of geometrical optics; this is illustrated in figure 8(b), calculated for k =0.05, corresponding to h0 = 5.2 nm.

  

European journal of physics, 27, 109. Retrieved from www.phy.bris.ac.uk/people/Berry_mv/the_papers/berry383.pdf Spatial Filters - Laplacian/Laplacian of Gaussian. (n.d.). Retrieved April 19, 2012, from homepages.inf.ed.ac.uk/rbf/HIPR2/log.htm Thompson, S. P. (1897). Light Visible and Invisible: A Series of Lectures at Royal Institution of Great Britain. Macmillan. Retrieved from www.archive.org/stream/lightvisibleinvi00thomuoft#page/50...

 

In the industrial and materialist period that began in the 19th century, Catholicism, even though it had to give in to its official positions, underwent glorious revival. In the years 1830-1880, an attempt was made to revive an authentic religious art, in the image of restored faith, through examples of medieval art. The Gothic cathedral, in its 13th century purity, Fra Angelico, the painter who paints on his knees, will be the models unceasingly questioned and translated through the teaching of Ingres.

 

MetaAI's attempt at identifying interesting objects in a photo of the sea floor under sea ice. It picks up the brittle star, urchin, worms and a sea spider really well. It also separates soft sediment from rock.

Queen Anne's lace and soldier beetle

Cantharidae beetle -- Coleoptera

Wellsville, New York

 

To see more of my "Inspiring Insects" set, click below:

www.flickr.com/photos/wolfraven/sets/72157605602154384/show

 

From Wikipedia:

 

"Soldier beetles are highly desired by gardeners as biological control agents of a number of pest insects. The larvae tend to be dark brown or gray, slender and wormlike with a rippled appearance due to pronounced segmentation. They consume grasshopper eggs, aphids, caterpillars and other soft bodied insects, most of which are pests.

 

"The adults are especially important predators of aphids. They supplement their diet with nectar and pollen and can be minor pollinators. Soldier beetle populations can be increased by planting good nectar- or pollen-producing plants such as Asclepias or Solidago.

 

"Historically, these beetles were placed in a superfamily "Cantharoidea", which has been subsumed by the superfamily Elateroidea; the name is still sometimes used as a rankless grouping, including the families Cantharidae, Drilidae, Lampyridae, Lycidae, Omalisidae, Omethidae, Phengodidae (which includes Telegeusidae), and Rhagophthalmidae."

  

A quick look at all of the SLR models from Nikon, from the flagship professional F3 at the front, to the newbie-oriented FG-20 at the rear.

Designed and folded by me from a single uncut square.

 

The first version of this design wasn't very efficient and there was some unused paper. I was able to add many more features, including abdomen segments, tarsi, and even antennae segmentation, all incorporated into the CP. I also made the antennae a little bit longer.

 

Folding this one took even longer than the original, which was already my most time-consuming design. I probably spent ~11 hours on this one.

 

CP: www.flickr.com/photos/156771525@N03/48498106496/in/datepo...

Fossil evidence suggests millipedes were the earliest animals to breathe air and make the move from an aquatic existence to walking on land; one of the first and largest invertebrates, they were 6 feet long, 1½ feet wide – a fossil specimen in siltstone from Scotland is the oldest with spiracles for breathing air

 

___________________________________________

American Giant Millipede – 2020SEP27 – Charlotte, NC

 

6-second video clip

 

Look what I found! A Giant Millipede, Narceus americanus: it grows twice as large as any other North American millipede, a cylindrical millipede (distinguished from flat millipedes), dark reddish-brown or black, a red line on each segmente edge; like all millipedes, they have 2 pairs of legs on most segments, rather than 1 pair of legs on each segment (like a centipede).

 

Does it bite? No (uniike a centipede). What about cyanide? Although not this species, some secrete hydrogen cyanide, quite poisonous. Remember, millipedes are toxic – but as long as they are not eaten, hands washed after touching them, they're pretty harmless; however, many have a defensive secretion, benzoquinone, that can cause chemical burns on human skin, generally mild, but powerful enough to cause temporary skin discoloration, itching, and blisters – some millipedes’ secretions are much more powerful, though.

 

The division of an animal into repeating body parts is called segmentation, clearly seen in millipedes, the word meaning “one thousand foot;” despite that name, millipedes with the most legs come up shy of the 1,000-leg mark, only about 750.

 

Hope you enjoy the 10% of 99 captures I took here this day!

Lagonda 2 1/2 Litre Tickford Drophead Coupe

as offered for the year 1952 in Europe North America

 

From humble beginnings to world class automobiles................

 

The Lagonda company was founded by in Staines, Middlesex, England in 1899 by an American opera singer, Wilbur Gunn, formerly from Springfield, Ohio. Lagonda was named for a small river near Springfield, Ohio.

 

In 1947 the company was taken over by David Brown and moved in with Aston Martin, which he had also bought, in Feltham, Middlesex. The old Staines works at Egham Hythe passed to Petters Limited, in which A.P. Good had acquired the controlling interest. Production restarted with the last model from W. O. Bentley, the 1948 2.6-Litre with new chassis featuring fully independent suspension. Its new 2580 cc twin overhead cam straight 6 became the basis for the Aston Martin engines of the 1950s. The engine grew to 3 litres in 1953 and continued to be available until 1958.

 

Production of this particular model began in 1948 under direction of David Brown. Total production of this Drop Head Coupe was from 1948 to 1952 (some were sold as 1953 models). A total of only 118 models were produced during this period.

 

This car

 

Body Design .......................................... Frank Feeley

 

Coachwork by ...................................... Tickford / England

 

Engine Design ...................................... W.O. Bentley

 

Chassis by ................................................. Lagonda

 

Source www.rtmrestorations.com

  

General Specifications

 

Production/sales period of cars with this particular specs: ...........................................................1948 - 1952

 

Modelyears: ...................................................................... 1949-1952

 

Country of origin: ..............................................GB United Kingdom

 

Make: .................................................................................... Lagonda

 

Model: ........................................................... 2 1/2 Litre - 1948-1953

 

Submodel: ....................................... 2 1/2 Litre Drophead Coupe

 

Optional equipment:

 

EEC segmentation: ................................................ F (luxury cars)

 

Class: ............................................ mid-size luxury / executive car

 

Body style: .................................................................. convertible

 

Doors: ...................................................................................... 2

 

Traction: ................................................ RWD (rear- wheel drive)

  

Basic dimension

 

Length: ................................................................. 4775 mm / 188 in

 

Width: ..................................................................... 1727 mm / 68 in

 

Height: ................................................................... 1549 mm / 61 in

 

Wheelbase: ..................................................... 2883 mm / 113.5 in

 

Fuel capacity: .................... 86 liter / 22.7 U.S. gal / 18.9 imp. gal

 

Powertrain

 

Engine manufacturer: ................... Lagonda Straight-6 2.6-Litre

 

Engine type: ............................................ spark-ignition 4-stroke

 

Fuel type: ......................................................... petrol (gasoline)

 

Fuel system: .......................... 2 carburetors naturally aspirated

 

Valves per cylinder: .............................................................. 2

 

Displacement: .......................................... 2580 cm3 / 157.2 cui

 

Power gross: ................. 78 kW / 106 PS / 105 hp (SAE) / 5000

 

Torque gross: ....................................... 180 Nm / 133 ft-lb / 2750

 

Source

www.automobile-catalog.com/car/1952/1370375/lagonda_2_12_...

 

High quality prints of this artwork are available here

A 20 year line-up of ASIMO humanoids... The early models look like a variety of Star Wars droids.

 

In this video clip video from the Honda labs, ASIMO looks like a child reaching out for a toy.

 

From Cognitive Computing ’07 in Berkeley today:

 

“Cognitive Computing is about engineering the mind by reverse engineering the brain.”

 

I ended my talk with a quote from Danny Hillis in The Pattern on the Stone:

“We will not engineer an artificial intelligence; rather we will set up the right conditions under which an intelligence can emerge. The greatest achievement of our technology may well be creation of tools that allow us to go beyond engineering – that allow us to create more than we can understand.”

 

Quotes from the Honda Research Institute talk, my favorite of the morning:

• for Honda, intelligence is a technology

• the essence of brain-like intelligence lies in the global organisation and self-referential control of processing

• following the analysis by synthesis principle, we verify our large scale hypotheses on our demonstrators in direct interaction with their environment

• in our strategy we approach the problem on several different levels of system organisation: macroscopic, mesoscopic, microscopic, microscopic & developmental

• first results confirm our approach to brain-like intelligent systems

• Open question: what is the role of the substrate? How close must a successful interpretation of the brain (in a technical sense) be to its underlying bio-chemical processes

 

Intelligence is a technology and a strategy for

• robust and flexible problem solving

• under resource limitations (time, energy)

• in complex environments (natural and artificial)

 

• the brain is the only intelligent system that we know of

• robots with rich environmental interaction provide us for the 1st time with the

means to study and verify large-scale hypotheses on brain-like intelligence

• our approach is to build the brain to understand the brain – the analysis by synthesis principle

• the brain is the most complex structure ever investigated by science

• it is not suitable to the most successful scientific analysis by decomposition

• the brain exhibits structural, chemical, plastic and dynamical complexity all intertwinned on different levels

• all processes in the brain are a result of information processing in a bio-chemical environment

• understanding the brain means unravelling the meaning of ourselves(related to cosmology)

 

brain = control system for organizing behavior

 

1) animals without cortex: autonomous systems (reflex automatons)

• genetically encoded reflex hierarchy with the limbic system at the top

• value system = genetically encoded mapping of sensory trigger features to behavioral prototypes

 

2) animals with cortex: flexible autonomous systems (learning systems)

reflex automaton +

• general memory architecture for storing experience

• genetically encoded self-referential control architecture

 

The stack [like OSI stack]:

 

A)Evo/Devo

Function:

• task embedded controlled cellular growth

• evolvable structures of spiking neural systems

• evolution of learning

• extract principles of simple brain evolution

 

Principles:

• co-evolution of genetic control and information expression

• evolutionary situated design

• selection driven interaction between evolution and learning

• major structural transitions of the co-evolution of early nervous systems and morphology

 

B) Microscopic Control Level

Function:

• elementary cortical processor

• rapid forward processing

• mixing prediction into afferent stream

• epochs of clocked, within asynchronous processing

 

Principles:

• spiking neurons

• cortical columnar architecture

• relative latency encoding

• rhythmic control of spike processing

 

Cortical development

• System architecture develops top-down.

• The basic control structure of the final system is present from the beginning.

• Development is marked by increasing sensory resolution and specialization of analysis, representation and control.

 

Self-referential Control Architecture

Minicolumn as elementary cortical processor

• mediates mixing of experience into afferent stream

• generates and synchronises rhythmic control for self-referential decomposition and learning

• relative spike latency encoding to control association width

 

The interplay between cortex and hippocampus increases memory capacity.

How does the cortex learn with:

• high memory capacity,

• fast retrieval speed, and

• high noise tolerance?

1. Store association A→B with HC (low memory capacity)

2. HC replays A→B to induce structural plasticity in cortex

3. Association A→B is stored in high-capacity cortical connections.

⇒ Structural plasticity leads to

- 10-20x memory capacity

- faster recall

- sparse connectivity

Short term memory is photographic — limited and inefficient — for a limited number of objects. Transferred to long term with more efficient and robust encoding.

  

C) Mesoscopic Control Level

Exploring, Learning and Understanding Visual Scenes

Function:

• active vision: fixation, saccading, tracking

• robust recognition and autonomous learning

• working memory and internal simulation

• self-organization of knowledge representation

 

Principles:

• columnar organization of multi-layered networks

• integration of different sensory analysis pathways

• stacked associative memories

• flexible selection of best-performing modular processing architecture (prediction, system monitoring)

• knowledge representation in task-related metric

 

Active Vision

• Decompose the sensory input into features & objects

• Use motion to distinguish foreground and background

• Compose a description of a scene

• Fixation by bottom-up & top-down attention

• Scan path & tracking

• Segmentation & prediction from movement

• Dynamic scene memory

 

D) Macroscopic Control Level

Function:

• self-development of practical intelligence

• autonomous interaction with environment

• a system that evolves itself from few innate abilities towards an autonomous and socially compliant partner

 

Principles:

• macroscopic architecture of the human brain

• child-like developmental strategy of learning

• integration of system components in a growing architecture

• self-referential control of learning

• a priori value system shaped by experience

 

Developing Intelligence

• Child-like Acquisition of Representation and Language

 

Crossing the Levels

A-B) evolution of spiking neural systems

B-C) mixing of top-down prediction into afferent signal stream and active sensing and

online learning

A-D) evolutionary optimisation of functional modules

 

This research team in Frankfurt: 36 full time scientists + 52 students and interns

 

Q&A:

Q: How about building in a heart, or the machines will destroy us?

A: With emotion: we show our internal state

Value system. Map unknown input to output. Interaction with environment

 

Q from Stanford Prof. about vision:

A: We take several views of a 2D representation instead of building a 3D model

 

Q from Lloyd Watts: Do you use a spiking neuron model?

A: No. Open question: spiking neuron model, is it important? We are limited by computational resources.

 

Q from IBM Almaden: Can’t Asimo can use better arithmetic engines than the human brain

A: Hmmm…. We have not thought about teaching Asimo arithmetic. Good question. I will keep it in mind and pose the question to the robot.

 

Honda’s History of Humanoids provides a slider linking to great photos of their 20 year developmental effort.

Cube houses, Rotterdam, 1984. Architecture by Piet Blom.

 

Our current exhibition on Dutch structuralism sparked a new interest for this type of architecture. Although I don’t particularly like it from an estheticial point of view, the segmentation, in order to create ‘human scaled’ spaces that invite residents to meet and interact with each other, allows for multiple perspectives and seemingly endless photographic possibilities.

 

Under the title of ‘Living as an Urban Roof’, Blom designed a city composed primarily of two levels: a public space on the ground floor and habitats above, forming ‘the roof of the city’.

Cikuan Bra fishtail wedding, suffused with a soft sheen satin belt with good visual segmentation add layering, simple fishtail skirt lined sketched out the bride graceful posture, nestled in the tissue, akinds of the looming beauty, particularly sultry.

Argiope bruennichi (wasp spider) is a species of orb-web spider distributed throughout central Europe, northern Europe, north Africa, parts of Asia, and the Azores archipelago. Like many other members of the genus Argiope (including St Andrew's Cross spiders), it shows striking yellow and black markings on its abdomen.

 

WEB

The spider builds a spiral orb web at dawn or dusk, commonly in long grass a little above ground level, taking it approximately an hour. The prominent zigzag shape called the stabilimentum, or web decoration, featured at the centre of the orb is of uncertain function, though it may be to attract insects.

 

When a prey item is first caught in the web, Argiope bruennichi will quickly immobilise its prey by wrapping it in silk. The prey is then bitten and then injected with a paralysing venom and a protein-dissolving enzyme.

 

POPULATION

During Summer 2006, research was carried out in the UK to find that there has been an influx of these spiders to the UK. The colour is still similar, although the yellow stripes are a bit more cream-coloured.

 

Besides the nominate subspecies, there is one subspecies currently recognised:

 

Argiope bruennichi nigrofasciata Franganillo, 1910 (Portugal)

 

SEXUAL DIMORPHISM

Argiope bruennichi display a rather large distinction between males and females with males averaging length of approximately 4.5 mm and females averaging 15 mm. The reasons for this large difference has evolutionary and fitness background with regards to mating as well as cannibalism by the females towards the males after copulation.

 

MATING

The differences of size of these male spiders actually allows the males to come into contact with the females in relation to their orb webs. The male Argiope bruennichi are able to enter into the female's orb and thus make their webs without being detected as prey and thus eaten before they are able to mate, a major fitness advantage.

 

PLUGGING

Certain male Argiope bruennichi have an adaptation that they have developed to ensure that they will be the only mate with whom the female can produce offspring. Certain males are able to "plug" the female after they have mated with her to prevent other males from copulating with the female. This plugging involves losing one of his pedipalps, thus allowing him to only mate twice. This is a major reason as to why these males are always in a rush to mate after the female has completed her final moult. With males always waiting around for the female to reach full maturity, the race is on for the male who is small enough to not be detected, yet is also able to "plug" the female so that other males have a lower chance of competing for fertilization of her eggs. These spiders have evolved to become monogamous for the most part after mating because of this damage.

 

If the females are only able to reproduce once they must develop a method to produce more offspring at one time (per clutch). This can be caused by multiple things, including a sex ratio that forces these males to make sure they have at least one female to produce their offspring simply because there are not as many females present.[5] If these females are only able to mate one time, they need to develop this larger clutch size to ensure that their genes are passed down from the surviving of her first clutch.

 

Females that consumed a small supplement of dietary essential amino acids produced offspring that survived simulated overwintering conditions significantly longer than offspring of other treatments. Results suggest that dietary essential amino acids, which may be sequestered by males from their diet, could be valuable supplements that increase the success of the offspring of cannibalistic females.

 

CANNIBALISM

The species Argiope bruennichi displays cannibalism when it comes to mating. We can see this because the sex ratio is so biased towards females later in the mating season. With so few females available, the males need to develop their own ways to potentially find and secure a successful mating like small size and proper time to find an immature female. The females, typically much larger in size when compared to the males, almost always consume their male counterpart after copulation. Males can often be seen in or near a female's web waiting for her to complete her final moult, at which time she reaches sexual maturity. At this time her chelicerae (jaws) will be soft for a short time and the male may mate with the female without the danger of being eaten. These males obviously want to avoid getting eaten and this is more or less the only time that they are able to take advantage. Although the cause for this type of dimorphism between sexes seems to have a much larger benefit for the females.

________________________________________

 

Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms. Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. As of November 2015, at least 45,700 spider species, and 114 families have been recorded by taxonomists. However, there has been dissension within the scientific community as to how all these families should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.

 

Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.

 

Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appeared in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets. True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving suborder, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before 200 million years ago.

 

A herbivorous species, Bagheera kiplingi, was described in 2008,[5] but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, and they liquefy their food by flooding it with digestive enzymes and grinding it with the bases of their pedipalps, as they do not have true jaws.

 

Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity.

 

While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers. An abnormal fear of spiders is called arachnophobia.

 

BODY PLAN

Spiders are chelicerates and therefore arthropods.[6] As arthropods they have: segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo. Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the cephalothorax or prosoma, is a complete fusion of the segments that in an insect would form two separate tagmata, the head and thorax; the rear tagma is called the abdomen or opisthosoma. In spiders, the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel. The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods. In fact, chelicerates' only appendages ahead of the mouth are a pair of chelicerae, and they lack anything that would function directly as "jaws". The first appendages behind the mouth are called pedipalps, and serve different functions within different groups of chelicerates.

 

Spiders and scorpions are members of one chelicerate group, the arachnids. Scorpions' chelicerae have three sections and are used in feeding. Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use. The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food.[8] Scorpions' pedipalps generally form large claws for capturing prey, while those of spiders are fairly small appendages whose bases also act as an extension of the mouth; in addition, those of male spiders have enlarged last sections used for sperm transfer.

 

In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk. The upper surface of the cephalothorax is covered by a single, convex carapace, while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface.

 

CIRCULATION AND RESPIRATION

Like other arthropods, spiders are coelomates in which the coelom is reduced to small areas round the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows. The heart is a tube in the upper part of the body, with a few ostia that act as non-return valves allowing blood to enter the heart from the hemocoel but prevent it from leaving before it reaches the front end. However, in spiders, it occupies only the upper part of the abdomen, and blood is discharged into the hemocoel by one artery that opens at the rear end of the abdomen and by branching arteries that pass through the pedicle and open into several parts of the cephalothorax. Hence spiders have open circulatory systems. The blood of many spiders that have book lungs contains the respiratory pigment hemocyanin to make oxygen transport more efficient.

 

Spiders have developed several different respiratory anatomies, based on book lungs, a tracheal system, or both. Mygalomorph and Mesothelae spiders have two pairs of book lungs filled with haemolymph, where openings on the ventral surface of the abdomen allow air to enter and diffuse oxygen. This is also the case for some basal araneomorph spiders, like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs. The trachea system has most likely evolved in small ancestors to help resist desiccation. The trachea were originally connected to the surroundings through a pair of openings called spiracles, but in the majority of spiders this pair of spiracles has fused into a single one in the middle, and moved backwards close to the spinnerets. Spiders that have tracheae generally have higher metabolic rates and better water conservation. Spiders are ectotherms, so environmental temperatures affect their activity.

 

FEEDING, DIGESTION AND EXCRETION

Uniquely among chelicerates, the final sections of spiders' chelicerae are fangs, and the great majority of spiders can use them to inject venom into prey from venom glands in the roots of the chelicerae. The family Uloboridae has lost its venom glands, and kills its prey with silk instead. Like most arachnids, including scorpions, spiders have a narrow gut that can only cope with liquid food and spiders have two sets of filters to keep solids out. They use one of two different systems of external digestion. Some pump digestive enzymes from the midgut into the prey and then suck the liquified tissues of the prey into the gut, eventually leaving behind the empty husk of the prey. Others grind the prey to pulp using the chelicerae and the bases of the pedipalps, while flooding it with enzymes; in these species, the chelicerae and the bases of the pedipalps form a preoral cavity that holds the food they are processing.

 

The stomach in the cephalothorax acts as a pump that sends the food deeper into the digestive system. The mid gut bears many digestive ceca, compartments with no other exit, that extract nutrients from the food; most are in the abdomen, which is dominated by the digestive system, but a few are found in the cephalothorax.

 

Most spiders convert nitrogenous waste products into uric acid, which can be excreted as a dry material. Malphigian tubules ("little tubes") extract these wastes from the blood in the hemocoel and dump them into the cloacal chamber, from which they are expelled through the anus. Production of uric acid and its removal via Malphigian tubules are a water-conserving feature that has evolved independently in several arthropod lineages that can live far away from water, for example the tubules of insects and arachnids develop from completely different parts of the embryo. However, a few primitive spiders, the sub-order Mesothelae and infra-order Mygalomorphae, retain the ancestral arthropod nephridia ("little kidneys"), which use large amounts of water to excrete nitrogenous waste products as ammonia.

 

CENTRAL NERVOUS SYSTEM

The basic arthropod central nervous system consists of a pair of nerve cords running below the gut, with paired ganglia as local control centers in all segments; a brain formed by fusion of the ganglia for the head segments ahead of and behind the mouth, so that the esophagus is encircled by this conglomeration of ganglia. Except for the primitive Mesothelae, of which the Liphistiidae are the sole surviving family, spiders have the much more centralized nervous system that is typical of arachnids: all the ganglia of all segments behind the esophagus are fused, so that the cephalothorax is largely filled with nervous tissue and there are no ganglia in the abdomen; in the Mesothelae, the ganglia of the abdomen and the rear part of the cephalothorax remain unfused.

 

Despite the relatively small central nervous system, some spiders (like Portia) exhibit complex behaviour, including the ability to use a trial-and-error approach.

Sense organs

 

EYES

Most spiders have four pairs of eyes on the top-front area of the cephalothorax, arranged in patterns that vary from one family to another. The pair at the front are of the type called pigment-cup ocelli ("little eyes"), which in most arthropods are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup. However, the main eyes at the front of spiders' heads are pigment-cup ocelli that are capable of forming images. The other eyes are thought to be derived from the compound eyes of the ancestral chelicerates, but no longer have the separate facets typical of compound eyes. Unlike the main eyes, in many spiders these secondary eyes detect light reflected from a reflective tapetum lucidum, and wolf spiders can be spotted by torch light reflected from the tapeta. On the other hand, jumping spiders' secondary eyes have no tapeta. Some jumping spiders' visual acuity exceeds by a factor of ten that of dragonflies, which have by far the best vision among insects; in fact the human eye is only about five times sharper than a jumping spider's. They achieve this by a telephoto-like series of lenses, a four-layer retina and the ability to swivel their eyes and integrate images from different stages in the scan. The downside is that the scanning and integrating processes are relatively slow.

 

There are spiders with a reduced number of eyes, of these those with six-eyes are the most numerous and are missing a pair of eyes on the anterior median line, others species have four-eyes and some just two. Cave dwelling species have no eyes, or possess vestigial eyes incapable of sight.

 

OTHER SENSES

As with other arthropods, spiders' cuticles would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly bristles called setae, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell, often by means of setae. Pedipalps carry a large number of such setae sensitive to contact chemicals and air-borne smells, such as female pheromones. Spiders also have in the joints of their limbs slit sensillae that detect forces and vibrations. In web-building spiders, all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively.

 

Like most arthropods, spiders lack balance and acceleration sensors and rely on their eyes to tell them which way is up. Arthropods' proprioceptors, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well understood. On the other hand, little is known about what other internal sensors spiders or other arthropods may have.

 

LOCMOTION

Each of the eight legs of a spider consists of seven distinct parts. The part closest to and attaching the leg to the cephalothorax is the coxa; the next segment is the short trochanter that works as a hinge for the following long segment, the femur; next is the spider's knee, the patella, which acts as the hinge for the tibia; the metatarsus is next, and it connects the tibia to the tarsus (which may be thought of as a foot of sorts); the tarsus ends in a claw made up of either two or three points, depending on the family to which the spider belongs. Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, spiders and a few other groups still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors. The only extensor muscles in spider legs are located in the three hip joints (bordering the coxa and the trochanter). As a result, a spider with a punctured cephalothorax cannot extend its legs, and the legs of dead spiders curl up. Spiders can generate pressures up to eight times their resting level to extend their legs, and jumping spiders can jump up to 50 times their own length by suddenly increasing the blood pressure in the third or fourth pair of legs. Although larger spiders use hydraulics to straighten their legs, unlike smaller jumping spiders they depend on their flexor muscles to generate the propulsive force for their jumps.

 

Most spiders that hunt actively, rather than relying on webs, have dense tufts of fine hairs between the paired claws at the tips of their legs. These tufts, known as scopulae, consist of bristles whose ends are split into as many as 1,000 branches, and enable spiders with scopulae to walk up vertical glass and upside down on ceilings. It appears that scopulae get their grip from contact with extremely thin layers of water on surfaces.[8] Spiders, like most other arachnids, keep at least four legs on the surface while walking or running.

 

SILK PRODUCTION

The abdomen has no appendages except those that have been modified to form one to four (usually three) pairs of short, movable spinnerets, which emit silk. Each spinneret has many spigots, each of which is connected to one silk gland. There are at least six types of silk gland, each producing a different type of silk.

 

Silk is mainly composed of a protein very similar to that used in insect silk. It is initially a liquid, and hardens not by exposure to air but as a result of being drawn out, which changes the internal structure of the protein. It is similar in tensile strength to nylon and biological materials such as chitin, collagen and cellulose, but is much more elastic. In other words, it can stretch much further before breaking or losing shape.

 

Some spiders have a cribellum, a modified spinneret with up to 40,000 spigots, each of which produces a single very fine fiber. The fibers are pulled out by the calamistrum, a comb-like set of bristles on the jointed tip of the cribellum, and combined into a composite woolly thread that is very effective in snagging the bristles of insects. The earliest spiders had cribella, which produced the first silk capable of capturing insects, before spiders developed silk coated with sticky droplets. However, most modern groups of spiders have lost the cribellum.

 

Tarantulas also have silk glands in their feet.

 

Even species that do not build webs to catch prey use silk in several ways: as wrappers for sperm and for fertilized eggs; as a "safety rope"; for nest-building; and as "parachutes" by the young of some species.

 

REPRODUCTION AND LIFE CYCLE

Spiders reproduce sexually and fertilization is internal but indirect, in other words the sperm is not inserted into the female's body by the male's genitals but by an intermediate stage. Unlike many land-living arthropods, male spiders do not produce ready-made spermatophores (packages of sperm), but spin small sperm webs on to which they ejaculate and then transfer the sperm to special syringe-like structures, palpal bulbs or palpal organs, borne on the tips of the pedipalps of mature males. When a male detects signs of a female nearby he checks whether she is of the same species and whether she is ready to mate; for example in species that produce webs or "safety ropes", the male can identify the species and sex of these objects by "smell".

 

Spiders generally use elaborate courtship rituals to prevent the large females from eating the small males before fertilization, except where the male is so much smaller that he is not worth eating. In web-weaving species, precise patterns of vibrations in the web are a major part of the rituals, while patterns of touches on the female's body are important in many spiders that hunt actively, and may "hypnotize" the female. Gestures and dances by the male are important for jumping spiders, which have excellent eyesight. If courtship is successful, the male injects his sperm from the palpal bulbs into the female's genital opening, known as the epigyne, on the underside of her abdomen. Female's reproductive tracts vary from simple tubes to systems that include seminal receptacles in which females store sperm and release it when they are ready.

 

Males of the genus Tidarren amputate one of their palps before maturation and enter adult life with one palp only. The palps are 20% of male's body mass in this species, and detaching one of the two improves mobility. In the Yemeni species Tidarren argo, the remaining palp is then torn off by the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime, the female feeds on the palpless male. In over 60% of cases, the female of the Australian redback spider kills and eats the male after it inserts its second palp into the female's genital opening; in fact, the males co-operate by trying to impale themselves on the females' fangs. Observation shows that most male redbacks never get an opportunity to mate, and the "lucky" ones increase the likely number of offspring by ensuring that the females are well-fed. However, males of most species survive a few matings, limited mainly by their short life spans. Some even live for a while in their mates' webs.

 

Females lay up to 3,000 eggs in one or more silk egg sacs, which maintain a fairly constant humidity level. In some species, the females die afterwards, but females of other species protect the sacs by attaching them to their webs, hiding them in nests, carrying them in the chelicerae or attaching them to the spinnerets and dragging them along.

 

Baby spiders pass all their larval stages inside the egg and hatch as spiderlings, very small and sexually immature but similar in shape to adults. Some spiders care for their young, for example a wolf spider's brood cling to rough bristles on the mother's back, and females of some species respond to the "begging" behaviour of their young by giving them their prey, provided it is no longer struggling, or even regurgitate food.

 

Like other arthropods, spiders have to molt to grow as their cuticle ("skin") cannot stretch. In some species males mate with newly molted females, which are too weak to be dangerous to the males. Most spiders live for only one to two years, although some tarantulas can live in captivity for over 20 years.

 

SIZE

Spiders occur in a large range of sizes. The smallest, Patu digua from Colombia, are less than 0.37 mm in body length. The largest and heaviest spiders occur among tarantulas, which can have body lengths up to 90 mm and leg spans up to 250 mm.

 

COLORATION

Only three classes of pigment (ommochromes, bilins and guanine) have been identified in spiders, although other pigments have been detected but not yet characterized. Melanins, carotenoids and pterins, very common in other animals, are apparently absent. In some species, the exocuticle of the legs and prosoma is modified by a tanning process, resulting in brown coloration. Bilins are found, for example, in Micrommata virescens, resulting in its green color. Guanine is responsible for the white markings of the European garden spider Araneus diadematus. It is in many species accumulated in specialized cells called guanocytes. In genera such as Tetragnatha, Leucauge, Argyrodes or Theridiosoma, guanine creates their silvery appearance. While guanine is originally an end-product of protein metabolism, its excretion can be blocked in spiders, leading to an increase in its storage. Structural colors occur in some species, which are the result of the diffraction, scattering or interference of light, for example by modified setae or scales. The white prosoma of Argiope results from hairs reflecting the light, Lycosa and Josa both have areas of modified cuticle that act as light reflectors.

 

ECOGOGY AND BEHAVIOR

NON-PREDATORY FEEDING

Although spiders are generally regarded as predatory, the jumping spider Bagheera kiplingi gets over 90% of its food from fairly solid plant material produced by acacias as part of a mutually beneficial relationship with a species of ant.

 

Juveniles of some spiders in the families Anyphaenidae, Corinnidae, Clubionidae, Thomisidae and Salticidae feed on plant nectar. Laboratory studies show that they do so deliberately and over extended periods, and periodically clean themselves while feeding. These spiders also prefer sugar solutions to plain water, which indicates that they are seeking nutrients. Since many spiders are nocturnal, the extent of nectar consumption by spiders may have been underestimated. Nectar contains amino acids, lipids, vitamins and minerals in addition to sugars, and studies have shown that other spider species live longer when nectar is available. Feeding on nectar avoids the risks of struggles with prey, and the costs of producing venom and digestive enzymes.

 

Various species are known to feed on dead arthropods (scavenging), web silk, and their own shed exoskeletons. Pollen caught in webs may also be eaten, and studies have shown that young spiders have a better chance of survival if they have the opportunity to eat pollen. In captivity, several spider species are also known to feed on bananas, marmalade, milk, egg yolk and sausages.

 

METHODS OF CAPTURING PREY

The best-known method of prey capture is by means of sticky webs. Varying placement of webs allows different species of spider to trap different insects in the same area, for example flat horizontal webs trap insects that fly up from vegetation underneath while flat vertical webs trap insects in horizontal flight. Web-building spiders have poor vision, but are extremely sensitive to vibrations.

 

Females of the water spider Argyroneta aquatica build underwater "diving bell" webs that they fill with air and use for digesting prey, molting, mating and raising offspring. They live almost entirely within the bells, darting out to catch prey animals that touch the bell or the threads that anchor it. A few spiders use the surfaces of lakes and ponds as "webs", detecting trapped insects by the vibrations that these cause while struggling.

 

Net-casting spiders weave only small webs, but then manipulate them to trap prey. Those of the genus Hyptiotes and the family Theridiosomatidae stretch their webs and then release them when prey strike them, but do not actively move their webs. Those of the family Deinopidae weave even smaller webs, hold them outstretched between their first two pairs of legs, and lunge and push the webs as much as twice their own body length to trap prey, and this move may increase the webs' area by a factor of up to ten. Experiments have shown that Deinopis spinosus has two different techniques for trapping prey: backwards strikes to catch flying insects, whose vibrations it detects; and forward strikes to catch ground-walking prey that it sees. These two techniques have also been observed in other deinopids. Walking insects form most of the prey of most deinopids, but one population of Deinopis subrufa appears to live mainly on tipulid flies that they catch with the backwards strike.

 

Mature female bolas spiders of the genus Mastophora build "webs" that consist of only a single "trapeze line", which they patrol. They also construct a bolas made of a single thread, tipped with a large ball of very wet sticky silk. They emit chemicals that resemble the pheromones of moths, and then swing the bolas at the moths. Although they miss on about 50% of strikes, they catch about the same weight of insects per night as web-weaving spiders of similar size. The spiders eat the bolas if they have not made a kill in about 30 minutes, rest for a while, and then make new bolas. Juveniles and adult males are much smaller and do not make bolas. Instead they release different pheromones that attract moth flies, and catch them with their front pairs of legs.

 

The primitive Liphistiidae, the "trapdoor spiders" of the family Ctenizidae and many tarantulas are ambush predators that lurk in burrows, often closed by trapdoors and often surrounded by networks of silk threads that alert these spiders to the presence of prey. Other ambush predators do without such aids, including many crab spiders, and a few species that prey on bees, which see ultraviolet, can adjust their ultraviolet reflectance to match the flowers in which they are lurking. Wolf spiders, jumping spiders, fishing spiders and some crab spiders capture prey by chasing it, and rely mainly on vision to locate prey.Some jumping spiders of the genus Portia hunt other spiders in ways that seem intelligent, outflanking their victims or luring them from their webs. Laboratory studies show that Portia's instinctive tactics are only starting points for a trial-and-error approach from which these spiders learn very quickly how to overcome new prey species. However, they seem to be relatively slow "thinkers", which is not surprising, as their brains are vastly smaller than those of mammalian predators.Ant-mimicking spiders face several challenges: they generally develop slimmer abdomens and false "waists" in the cephalothorax to mimic the three distinct regions (tagmata) of an ant's body; they wave the first pair of legs in front of their heads to mimic antennae, which spiders lack, and to conceal the fact that they have eight legs rather than six; they develop large color patches round one pair of eyes to disguise the fact that they generally have eight simple eyes, while ants have two compound eyes; they cover their bodies with reflective hairs to resemble the shiny bodies of ants. In some spider species, males and females mimic different ant species, as female spiders are usually much larger than males. Ant-mimicking spiders also modify their behavior to resemble that of the target species of ant; for example, many adopt a zig-zag pattern of movement, ant-mimicking jumping spiders avoid jumping, and spiders of the genus Synemosyna walk on the outer edges of leaves in the same way as Pseudomyrmex. Ant-mimicry in many spiders and other arthropods may be for protection from predators that hunt by sight, including birds, lizards and spiders. However, several ant-mimicking spiders prey either on ants or on the ants' "livestock", such as aphids. When at rest, the ant-mimicking crab spider Amyciaea does not closely resemble Oecophylla, but while hunting it imitates the behavior of a dying ant to attract worker ants. After a kill, some ant-mimicking spiders hold their victims between themselves and large groups of ants to avoid being attacked.

 

DEFENSE

There is strong evidence that spiders' coloration is camouflage that helps them to evade their major predators, birds and parasitic wasps, both of which have good color vision. Many spider species are colored so as to merge with their most common backgrounds, and some have disruptive coloration, stripes and blotches that break up their outlines. In a few species, such as the Hawaiian happy-face spider, Theridion grallator, several coloration schemes are present in a ratio that appears to remain constant, and this may make it more difficult for predators to recognize the species. Most spiders are insufficiently dangerous or unpleasant-tasting for warning coloration to offer much benefit. However, a few species with powerful venoms, large jaws or irritant hairs have patches of warning colors, and some actively display these colors when threatened.

 

Many of the family Theraphosidae, which includes tarantulas and baboon spiders, have urticating hairs on their abdomens and use their legs to flick them at attackers. These hairs are fine setae (bristles) with fragile bases and a row of barbs on the tip. The barbs cause intense irritation but there is no evidence that they carry any kind of venom. A few defend themselves against wasps by including networks of very robust threads in their webs, giving the spider time to flee while the wasps are struggling with the obstacles. The golden wheeling spider, Carparachne aureoflava, of the Namibian desert escapes parasitic wasps by flipping onto its side and cartwheeling down sand dunes.

 

SOCIAL SPIDERS

A few spider species that build webs live together in large colonies and show social behavior, although not as complex as in social insects. Anelosimus eximius (in the family Theridiidae) can form colonies of up to 50,000 individuals. The genus Anelosimus has a strong tendency towards sociality: all known American species are social, and species in Madagascar are at least somewhat social. Members of other species in the same family but several different genera have independently developed social behavior. For example, although Theridion nigroannulatum belongs to a genus with no other social species, T. nigroannulatum build colonies that may contain several thousand individuals that co-operate in prey capture and share food. Other communal spiders include several Philoponella species (family Uloboridae), Agelena consociata (family Agelenidae) and Mallos gregalis (family Dictynidae). Social predatory spiders need to defend their prey against kleptoparasites ("thieves"), and larger colonies are more successful in this. The herbivorous spider Bagheera kiplingi lives in small colonies which help to protect eggs and spiderlings. Even widow spiders (genus Latrodectus), which are notoriously cannibalistic, have formed small colonies in captivity, sharing webs and feeding together.

 

WEB TYPES

There is no consistent relationship between the classification of spiders and the types of web they build: species in the same genus may build very similar or significantly different webs. Nor is there much correspondence between spiders' classification and the chemical composition of their silks. Convergent evolution in web construction, in other words use of similar techniques by remotely related species, is rampant. Orb web designs and the spinning behaviors that produce them are the best understood. The basic radial-then-spiral sequence visible in orb webs and the sense of direction required to build them may have been inherited from the common ancestors of most spider groups. However, the majority of spiders build non-orb webs. It used to be thought that the sticky orb web was an evolutionary innovation resulting in the diversification of the Orbiculariae. Now, however, it appears that non-orb spiders are a sub-group that evolved from orb-web spiders, and non-orb spiders have over 40% more species and are four times as abundant as orb-web spiders. Their greater success may be because sphecid wasps, which are often the dominant predators of spiders, much prefer to attack spiders that have flat webs.

 

ORB WEBS

About half the potential prey that hit orb webs escape. A web has to perform three functions: intercepting the prey (intersection), absorbing its momentum without breaking (stopping), and trapping the prey by entangling it or sticking to it (retention). No single design is best for all prey. For example: wider spacing of lines will increase the web's area and hence its ability to intercept prey, but reduce its stopping power and retention; closer spacing, larger sticky droplets and thicker lines would improve retention, but would make it easier for potential prey to see and avoid the web, at least during the day. However, there are no consistent differences between orb webs built for use during the day and those built for use at night. In fact, there is no simple relationship between orb web design features and the prey they capture, as each orb-weaving species takes a wide range of prey.

 

The hubs of orb webs, where the spiders lurk, are usually above the center, as the spiders can move downwards faster than upwards. If there is an obvious direction in which the spider can retreat to avoid its own predators, the hub is usually offset towards that direction.

 

Horizontal orb webs are fairly common, despite being less effective at intercepting and retaining prey and more vulnerable to damage by rain and falling debris. Various researchers have suggested that horizontal webs offer compensating advantages, such as reduced vulnerability to wind damage; reduced visibility to prey flying upwards, because of the back-lighting from the sky; enabling oscillations to catch insects in slow horizontal flight. However, there is no single explanation for the common use of horizontal orb webs.

 

Spiders often attach highly visible silk bands, called decorations or stabilimenta, to their webs. Field research suggests that webs with more decorative bands captured more prey per hour. However, a laboratory study showed that spiders reduce the building of these decorations if they sense the presence of predators.

 

There are several unusual variants of orb web, many of them convergently evolved, including: attachment of lines to the surface of water, possibly to trap insects in or on the surface; webs with twigs through their centers, possibly to hide the spiders from predators; "ladder-like" webs that appear most effective in catching moths. However, the significance of many variations is unclear.

 

In 1973, Skylab 3 took two orb-web spiders into space to test their web-spinning capabilities in zero gravity. At first, both produced rather sloppy webs, but they adapted quickly.

 

TANGLEWEB SPIDERS (COBWEB SPIDERS)

Members of the family Theridiidae weave irregular, tangled, three-dimensional webs, popularly known as cobwebs. There seems to be an evolutionary trend towards a reduction in the amount of sticky silk used, leading to its total absence in some species. The construction of cobwebs is less stereotyped than that of orb-webs, and may take several days.

 

OTHER TYPES OF WEBS

The Linyphiidae generally make horizontal but uneven sheets, with tangles of stopping threads above. Insects that hit the stopping threads fall onto the sheet or are shaken onto it by the spider, and are held by sticky threads on the sheet until the spider can attack from below.

 

EVOLUTION

FOSSIL RECORD

Although the fossil record of spiders is considered poor, almost 1000 species have been described from fossils. Because spiders' bodies are quite soft, the vast majority of fossil spiders have been found preserved in amber. The oldest known amber that contains fossil arthropods dates from 130 million years ago in the Early Cretaceous period. In addition to preserving spiders' anatomy in very fine detail, pieces of amber show spiders mating, killing prey, producing silk and possibly caring for their young. In a few cases, amber has preserved spiders' egg sacs and webs, occasionally with prey attached; the oldest fossil web found so far is 100 million years old. Earlier spider fossils come from a few lagerstätten, places where conditions were exceptionally suited to preserving fairly soft tissues.

 

The oldest known exclusively terrestrial arachnid is the trigonotarbid Palaeotarbus jerami, from about 420 million years ago in the Silurian period, and had a triangular cephalothorax and segmented abdomen, as well as eight legs and a pair of pedipalps. Attercopus fimbriunguis, from 386 million years ago in the Devonian period, bears the earliest known silk-producing spigots, and was therefore hailed as a spider at the time of its discovery. However, these spigots may have been mounted on the underside of the abdomen rather than on spinnerets, which are modified appendages and whose mobility is important in the building of webs. Hence Attercopus and the similar Permian arachnid Permarachne may not have been true spiders, and probably used silk for lining nests or producing egg-cases rather than for building webs. The largest known fossil spider as of 2011 is the araneid Nephila jurassica, from about 165 million years ago, recorded from Daohuogo, Inner Mongolia in China. Its body length is almost 25 mm.

 

Several Carboniferous spiders were members of the Mesothelae, a primitive group now represented only by the Liphistiidae. The mesothelid Paleothele montceauensis, from the Late Carboniferous over 299 million years ago, had five spinnerets. Although the Permian period 299 to 251 million years ago saw rapid diversification of flying insects, there are very few fossil spiders from this period.

 

The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the Triassic well before 200 million years ago. Some Triassic mygalomorphs appear to be members of the family Hexathelidae, whose modern members include the notorious Sydney funnel-web spider, and their spinnerets appear adapted for building funnel-shaped webs to catch jumping insects. Araneomorphae account for the great majority of modern spiders, including those that weave the familiar orb-shaped webs. The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families.

 

WIKIPEDIA

Three Legged Cross, Dorset

 

COLLEMBOLA (Springtails) > SYMPHYPLEONA >

Dicyrtomidae > Dicyrtominae > Dicyrtomina ornata

____________________________________________________

 

Hidden Worlds

COLLEMBOLA were previously classified with insects, but are now treated as a class in their own right, sitting alongside DIPLURA (the Two-pronged Bristletails) and PROTURA (Proturans or Coneheads). They are the wingless ARTHROPODS, which together with INSECTA are the four classes within the superclass HEXAPODA.

 

Springtails, the most abundant arthropods on earth, are very small wingless creatures, just a few millimetres long that live mainly in soil and leaf litter. They are so named due to their forked springing organ, or furca, which enables them to jump considerable distances of up to several centimetres when disturbed. They have reduced eyes, variable length antennae, simple bodies and short legs. They have two distinct forms; elongate in which the six abdomen segments are clearly visible, and globular bodies where the segmentation is far from apparent. There are around 250 species in Britain, the majority of which are so small that I wouldn’t even attempt to photograph them. However, there are a few in the 2-5mm range that are of interest and over the past few weeks I have managed to get some reasonable photos of some of them.

 

This is Dicyrtomina ornata, which is recorded as being common although I have only found two so far. It’s one of the globular-bodied species with a length of around 3mm. It is extremely similar to another species, Dicyrtomina saundersi apart from the shape of the dark pigmentation at the posterior end of the abdomen. In this species it is more of a solid patch, whereas in Dicyrtomina saundersi it is distinctly multi-barred.

 

Yau Ma Tei, Hong Kong

Leica M6 TTL Summaron 35mm f/2.8 Goggles

Kodak Tmax 100

Epson V700

Mesembryanthemum acinaciforme Linnaeus

Native to South Africa, but is naturalised in many other regions throughout the world, notably Australia, California and the Mediterranean, all of which share a similar climate. It is resistant to harsh coastal climatic conditions and to salt. It easily spreads by seed and from segmentation (any shoot segment can produce roots) and has escaped from cultivation and become an invasive species. It is now common along highways, beaches and in other landscapes. Parts of the coastline of many countries in mild climate areas are completely covered by this invasive plant that compete with native species.

 

Millipede legs push them forward in a wave-like motion

 

___________________________________________

American Giant Millipede – 2020SEP27 – Charlotte, NC

 

Look what I found! A Giant Millipede, Narceus americanus: it grows twice as large as any other North American millipede, a cylindrical millipede (distinguished from flat millipedes), dark reddish-brown or black, a red line on each segmente edge; like all millipedes, they have 2 pairs of legs on most segments, rather than 1 pair of legs on each segment (like a centipede).

 

Does it bite? No (uniike a centipede). What about cyanide? Although not this species, some secrete hydrogen cyanide, quite poisonous. Remember, millipedes are toxic – but as long as they are not eaten, hands washed after touching them, they're pretty harmless; however, many have a defensive secretion, benzoquinone, that can cause chemical burns on human skin, generally mild, but powerful enough to cause temporary skin discoloration, itching, and blisters – some millipedes’ secretions are much more powerful, though.

 

The division of an animal into repeating body parts is called segmentation, clearly seen in millipedes, the word meaning “one thousand foot;” despite that name, millipedes with the most legs come up shy of the 1,000-leg mark, only about 750.

 

Hope you enjoy the 10% of 99 captures I took here this day!

The Carpobrotus acinaciformis is particularly resistant to some harsh coastal climatic conditions and to salt where it may forms large monospecific zones. But due to the fact that it easily spreads by seed and from segmentation (any shoot segment can produce roots) it has escaped from cultivation and has become an invasive species.

 

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© www.tomjutte.tk

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+++ DISCLAIMER +++Nothing you see here is real, even though the conversion or the presented background story might be based on historical facts. BEWARE!

  

Some background:

The Nakajima J9N Kitsuka (中島 橘花, "Orange Blossom", pronounced Kikka in Kanji used traditionally by the Japanese) was Japan's first jet aircraft. In internal IJN documents it was also called Kōkoku Nigō Heiki (皇国二号兵器, "Imperial Weapon No.2"). After the Japanese military attaché in Germany witnessed trials of the Messerschmitt Me 262 in 1942, the Imperial Japanese Navy issued a request to Nakajima to develop a similar aircraft to be used as a fast attack bomber. Among the specifications for the design were the requirements that it should be able to be built largely by unskilled labor, and that the wings should be foldable. This latter feature was not intended for potential use on aircraft carriers, but rather to enable the aircraft to be hidden in caves and tunnels around Japan as the navy began to prepare for the defense of the home islands.

 

Nakajima designers Kazuo Ohno and Kenichi Matsumura laid out an aircraft that bore a strong but superficial resemblance to the Me 262. Compared to the Me 262, the J9N airframe was noticeably smaller and more conventional in design, with straight wings and tail surfaces, lacking the slight sweepback of the Me 262. The triangular fuselage cross section characteristic of the German design was less pronounced, due to smaller fuel tanks. The main landing gear of the Kikka was taken from the A6M Zero and the nose wheel from the tail of a Yokosuka P1Y bomber.

The Kikka was designed in preliminary form to use the Tsu-11, a rudimentary motorjet style jet engine that was essentially a ducted fan with an afterburner. Subsequent designs were planned around the Ne-10 (TR-10) centrifugal-flow turbojet, and the Ne-12, which added a four-stage axial compressor to the front of the Ne-10. Tests of this powerplant soon revealed that it would not produce anywhere near the power required to propel the aircraft, and the project was temporarily stalled. It was then decided to produce a new axial flow turbojet based on the German BMW 003.

 

Development of the engine was troubled, based on little more than photographs and a single cut-away drawing of the BMW 003. A suitable unit, the Ishikawa-jima Ne-20, was finally built in January 1945. By that time, the Kikka project was making progress and the first prototype made its maiden flight. Due to the worsening war situation, the Navy considered employing the Kikka as a kamikaze weapon, but this was quickly rejected due to the high cost and complexity associated with manufacturing contemporary turbojet engines. Other more economical projects designed specifically for kamikaze attacks, such as the simpler Nakajima Tōka (designed to absorb Japanese stock of obsolete engines), the pulsejet-powered Kawanishi Baika, and the infamous Yokosuka Ohka, were either underway or already in mass production.

 

The following month the prototype was dismantled and delivered to Kisarazu Naval Airfield where it was re-assembled and prepared for flight testing. The aircraft performed well during a 20-minute test flight, with the only concern being the length of the takeoff run – the Ne 20 only had a thrust of 4.66 kN (1,047 lbf), and the engine pair had barely sufficient power to get the aircraft off the ground. This lack of thrust also resulted in a maximum speed of just 623 km/h (387 mph, 336 kn) at sea level and 696 km/h (432 mph; 376 kn) at 10,000 m (32,808 ft).

For the second test flight, four days later, rocket assisted take off (RATO) units were fitted to the aircraft, which worked and gave the aircraft acceptable field performance. The tests went on, together with a second prototype, but despite this early test stage, the J9N was immediately rushed into production.

 

By May 1945 approximately forty airframes had been completed and handed over to IJN home defense frontline units for operational use and conversion training. These were structurally identical with the prototypes, but they were powered by more potent and reliable Ne-130 (with 8.826 kN/900 kgf) or Ne-230 (8.679 kN/885 kgf) engines, which finally gave the aircraft a competitive performance and also made the RATO boosters obsolete - unless an 800 kg bomb was carried in overload configuration. Most were J9N1 day fighter single seaters, armed with two 30 mm Type 5 cannons with 50 rounds per gun in the nose. Some operational Kitsukas had, due to the lack of equipment, the 30 mm guns replaced with lighter 20 mm Ho-5 cannon. A few were unarmed two-seaters (J9N2) with dual controls and a second seat instead of the fuselage fuel tank. This markedly limited the aircraft’s range but was accepted for a dedicated trainer, but a ventral 500 l drop tank could be carried to extend the two-seater’s range to an acceptable level.

 

A small number, both single- and two-seaters, were furthermore adapted to night fighter duties and equipped with an experimental ”FD-2” centimeter waveband radar in the nose with an “antler” antenna array, similar to German radar sets of the time. The FD-2 used four forward-facing Yagi style antennae with initially five and later with seven elements (the sideway facing rods) each. These consisted of two pairs, each with a sending (top and bot) and a receiving antenna (left and right). The set used horizontal lobe switching to find the target, an electrical shifter would continuously switch between the sets. The signal strengths would then be compared to determine the range and azimuth of the target, and the results would then be shown on a CRT display.

 

In order to fit the electronics (the FD-2 weighed around 70 kg/155 lb) the night fighters typically had one of the nose-mounted guns replaced by a fixed, obliquely firing Ho-5 gun ("Schräge Musik"-style), which was mounted in the aircraft’s flank behind the cockpit, and the 500l drop tank became a permanent installation to extend loiter time, at the expense of top speed, though. These machines received the suffix “-S” and flew, despite the FD-2’s weaknesses and limitations, a few quite effective missions against American B-29 bombers, but their impact was minimal due to the aircrafts’ small numbers and poor reliability of the still experimental radar system. However, the FD-2’s performance was rather underwhelming, though, with an insufficient range of only 3 km. Increased drag due to the antennae and countermeasures deployed by B-29 further decreased the effectiveness, and the J9N2-S’s successes could be rather attributed to experienced and motivated crews than the primitive radar.

 

Proposed follow-on J9N versions had included a reconnaissance aircraft and a fast attack aircraft that was supposed to carry a single bomb under the fuselage against ships. There was also a modified version of the design to be launched from a 200 m long catapult, the "Nakajima Kikka-kai Prototype Turbojet Special Attacker". All these proposed versions were expected to be powered by more advanced developments of the Ne-20, the Ne-330 with 13 kN (1.330 kg) thrust, but none of them reached the hardware stage.

 

The J9Ns’ overall war contribution was negligible, and after the war, several airframes (including partial airframes) were captured by Allied forces. Three airframes (including a two-seat night fighter with FD-2 radar) were brought to the U.S. for study. Today, two J9N examples survive in the National Air and Space Museum: The first is a Kikka that was taken to the Patuxent River Naval Air Base, Maryland for analysis. This aircraft is very incomplete and is believed to have been patched together from a variety of semi-completed airframes. It is currently still in storage at the Paul E. Garber Preservation, Restoration and Storage Facility in Silver Hill, MD. The second Kikka is on display at the NASM Udvar-Hazy Center in the Mary Baker Engen Restoration Hangar.

  

General characteristics:

Crew: 2

Length: 8.13 m (26 ft 8 in) fuselage only

10.30 m (33 ft 8¾ in) with FD-2 antenna array

Wingspan: 10 m (32 ft 10 in)

Height: 2.95 m (9 ft 8 in)

Wing area: 13.2 m² (142 sq ft)

Empty weight: 2,300 kg (5,071 lb)

Gross weight: 3,500 kg (7,716 lb)

Max takeoff weight: 4,080 kg (8,995 lb)

 

Powerplant:

2× Ishikawajima Ne-130 or Ne-230 axial-flow turbojet engines

each with 8.83 kN/900 kg or 8.68 kN/885 kg thrust

 

Performance:

Maximum speed: 785 km/h (487 mph, 426 kn)

Range: 925 km (574 mi, 502 nmi) with internal fuel

Service ceiling: 12,000 m (39,000 ft)

Rate of climb: 10.5 m/s (2,064 ft/min)

Wing loading: 265 kg/m² (54 lb/sq ft)

Thrust-to-weight ratio: 0.43

 

Armament:

1× 30 mm (1.181 in) Type 5 cannon with 50 rounds in the nose

1× 20 mm (0.787 in) Type Ho-2 cannon with 80 rounds, mounted obliquely behind the cockpit

1× ventral hardpoint for a 500 l drop tank or a single 500 kg (1,102 lb) bomb

  

The kit and its assembly:

This is in fact the second Kikka I have built, and this time it’s a two-seater from AZ Models – actually the trainer boxing, but converted into a personal night fighter interpretation. The AZ Models kit is a simple affair, but that's also its problem. In the box things look quite good, detail level is on par with a classic Matchbox kit. But unlike a Matchbox kit, the AZ Models offering does not go together well. I had to fight everywhere with poor fit, lack of locator pins, ejection marks - anything a short run model kit can throw at you! Thanks to the experience with the single-seater kit some time ago, things did not become too traumatic, but it’s still not a kit for beginners. What worked surprisingly well was the IP canopy, though, which I cut into five sections for an optional open display – even though I am not certain if the kit’s designers had put some brain into their work because the canopy’s segmentation becomes more and more dubious the further you go backwards.

 

The only personal mods is a slightly changed armament, with one nose gun deleted and faired over with a piece of styrene sheet, while the leftover gun was mounted obliquely onto the left flank. I initially considered a position behind the canopy but rejected this because of CoG reasons. Then I planned to mount it directly behind the 2nd seat, so that the barrel would protrude through the canopy, but this appeared unrealistic because the (utterly tiny) sliding canopy for the rear crewman could not have been opened anymore? Finally, I settled for an offset position in the aircraft’s flanks, partly inspired by “Schräge Musik” arrangements on some German Fw 190 night fighters.

 

The antennae come from a Jadar Model PE set for Italeri’s Me 210s, turning it either into a night fighter or a naval surveillance aircraft.

  

Painting and markings:

This became rather lusterless; many late IJN night fighters carried a uniform dark green livery with minimalistic, toned-down markings, e. g. hinomaru without a white high-contrast edge, just the yellow ID bands on the wings’ leading edges were retained.

For this look the model received an overall basis coat of Humbrol 75 (Bronze Green), later treated with a black ink washing, dry-brushed aluminum and post-shading with lighter shades of dark green (including Humbrol 116 and Revell 67). The only colorful highlight is a red fin tip (Humbrol 19) and a thin red stripe underneath (decal). The yellow and white ID bands were created with decal material.

 

The cockpit interior was painted in a yellowish-green primer (trying to simulate a typical “bamboo” shade that was used in some late-war IJN cockpits), while the landing gear wells were painted in aodake iro, a clear bluish protective lacquer. The landing gear struts themselves became semi-matt black.

 

The markings are fictional and were puzzled together from various sources. The hinomaru came from the AZ Models’ Kikka single seater sheet (since it offers six roundels w/o white edge), the tactical code on the fin was created with red numbers from a Fujimi Aichi B7A2 Ryusei.

 

Finally, the kit received a coat of matt acrylic varnish and some grinded graphite around the jet exhausts and the gun nozzles.

  

Well, this fictional Kikka night fighter looks quite dry, but that makes it IMHO more credible. The large antler antenna array might look “a bit too much”, and a real night fighter probably had a simpler arrangement with a single Yagi-style/arrow-shaped antenna, but a description of the FD-2 radar suggested the layout I chose – and it does not look bad. The oblique cannon in the flank is another odd detail, but it is not unplausible. However, with all the equipment and esp. the draggy antennae on board, the Kikka’s mediocre performance would surely have seriously suffered, probably beyond an effective use. But this is whifworld, after all. ;-)

+++ DISCLAIMER +++Nothing you see here is real, even though the conversion or the presented background story might be based on historical facts. BEWARE!

  

Some background:

The Nakajima J9N Kitsuka (中島 橘花, "Orange Blossom", pronounced Kikka in Kanji used traditionally by the Japanese) was Japan's first jet aircraft. In internal IJN documents it was also called Kōkoku Nigō Heiki (皇国二号兵器, "Imperial Weapon No.2"). After the Japanese military attaché in Germany witnessed trials of the Messerschmitt Me 262 in 1942, the Imperial Japanese Navy issued a request to Nakajima to develop a similar aircraft to be used as a fast attack bomber. Among the specifications for the design were the requirements that it should be able to be built largely by unskilled labor, and that the wings should be foldable. This latter feature was not intended for potential use on aircraft carriers, but rather to enable the aircraft to be hidden in caves and tunnels around Japan as the navy began to prepare for the defense of the home islands.

 

Nakajima designers Kazuo Ohno and Kenichi Matsumura laid out an aircraft that bore a strong but superficial resemblance to the Me 262. Compared to the Me 262, the J9N airframe was noticeably smaller and more conventional in design, with straight wings and tail surfaces, lacking the slight sweepback of the Me 262. The triangular fuselage cross section characteristic of the German design was less pronounced, due to smaller fuel tanks. The main landing gear of the Kikka was taken from the A6M Zero and the nose wheel from the tail of a Yokosuka P1Y bomber.

The Kikka was designed in preliminary form to use the Tsu-11, a rudimentary motorjet style jet engine that was essentially a ducted fan with an afterburner. Subsequent designs were planned around the Ne-10 (TR-10) centrifugal-flow turbojet, and the Ne-12, which added a four-stage axial compressor to the front of the Ne-10. Tests of this powerplant soon revealed that it would not produce anywhere near the power required to propel the aircraft, and the project was temporarily stalled. It was then decided to produce a new axial flow turbojet based on the German BMW 003.

 

Development of the engine was troubled, based on little more than photographs and a single cut-away drawing of the BMW 003. A suitable unit, the Ishikawa-jima Ne-20, was finally built in January 1945. By that time, the Kikka project was making progress and the first prototype made its maiden flight. Due to the worsening war situation, the Navy considered employing the Kikka as a kamikaze weapon, but this was quickly rejected due to the high cost and complexity associated with manufacturing contemporary turbojet engines. Other more economical projects designed specifically for kamikaze attacks, such as the simpler Nakajima Tōka (designed to absorb Japanese stock of obsolete engines), the pulsejet-powered Kawanishi Baika, and the infamous Yokosuka Ohka, were either underway or already in mass production.

 

The following month the prototype was dismantled and delivered to Kisarazu Naval Airfield where it was re-assembled and prepared for flight testing. The aircraft performed well during a 20-minute test flight, with the only concern being the length of the takeoff run – the Ne 20 only had a thrust of 4.66 kN (1,047 lbf), and the engine pair had barely sufficient power to get the aircraft off the ground. This lack of thrust also resulted in a maximum speed of just 623 km/h (387 mph, 336 kn) at sea level and 696 km/h (432 mph; 376 kn) at 10,000 m (32,808 ft).

For the second test flight, four days later, rocket assisted take off (RATO) units were fitted to the aircraft, which worked and gave the aircraft acceptable field performance. The tests went on, together with a second prototype, but despite this early test stage, the J9N was immediately rushed into production.

 

By May 1945 approximately forty airframes had been completed and handed over to IJN home defense frontline units for operational use and conversion training. These were structurally identical with the prototypes, but they were powered by more potent and reliable Ne-130 (with 8.826 kN/900 kgf) or Ne-230 (8.679 kN/885 kgf) engines, which finally gave the aircraft a competitive performance and also made the RATO boosters obsolete - unless an 800 kg bomb was carried in overload configuration. Most were J9N1 day fighter single seaters, armed with two 30 mm Type 5 cannons with 50 rounds per gun in the nose. Some operational Kitsukas had, due to the lack of equipment, the 30 mm guns replaced with lighter 20 mm Ho-5 cannon. A few were unarmed two-seaters (J9N2) with dual controls and a second seat instead of the fuselage fuel tank. This markedly limited the aircraft’s range but was accepted for a dedicated trainer, but a ventral 500 l drop tank could be carried to extend the two-seater’s range to an acceptable level.

 

A small number, both single- and two-seaters, were furthermore adapted to night fighter duties and equipped with an experimental ”FD-2” centimeter waveband radar in the nose with an “antler” antenna array, similar to German radar sets of the time. The FD-2 used four forward-facing Yagi style antennae with initially five and later with seven elements (the sideway facing rods) each. These consisted of two pairs, each with a sending (top and bot) and a receiving antenna (left and right). The set used horizontal lobe switching to find the target, an electrical shifter would continuously switch between the sets. The signal strengths would then be compared to determine the range and azimuth of the target, and the results would then be shown on a CRT display.

 

In order to fit the electronics (the FD-2 weighed around 70 kg/155 lb) the night fighters typically had one of the nose-mounted guns replaced by a fixed, obliquely firing Ho-5 gun ("Schräge Musik"-style), which was mounted in the aircraft’s flank behind the cockpit, and the 500l drop tank became a permanent installation to extend loiter time, at the expense of top speed, though. These machines received the suffix “-S” and flew, despite the FD-2’s weaknesses and limitations, a few quite effective missions against American B-29 bombers, but their impact was minimal due to the aircrafts’ small numbers and poor reliability of the still experimental radar system. However, the FD-2’s performance was rather underwhelming, though, with an insufficient range of only 3 km. Increased drag due to the antennae and countermeasures deployed by B-29 further decreased the effectiveness, and the J9N2-S’s successes could be rather attributed to experienced and motivated crews than the primitive radar.

 

Proposed follow-on J9N versions had included a reconnaissance aircraft and a fast attack aircraft that was supposed to carry a single bomb under the fuselage against ships. There was also a modified version of the design to be launched from a 200 m long catapult, the "Nakajima Kikka-kai Prototype Turbojet Special Attacker". All these proposed versions were expected to be powered by more advanced developments of the Ne-20, the Ne-330 with 13 kN (1.330 kg) thrust, but none of them reached the hardware stage.

 

The J9Ns’ overall war contribution was negligible, and after the war, several airframes (including partial airframes) were captured by Allied forces. Three airframes (including a two-seat night fighter with FD-2 radar) were brought to the U.S. for study. Today, two J9N examples survive in the National Air and Space Museum: The first is a Kikka that was taken to the Patuxent River Naval Air Base, Maryland for analysis. This aircraft is very incomplete and is believed to have been patched together from a variety of semi-completed airframes. It is currently still in storage at the Paul E. Garber Preservation, Restoration and Storage Facility in Silver Hill, MD. The second Kikka is on display at the NASM Udvar-Hazy Center in the Mary Baker Engen Restoration Hangar.

  

General characteristics:

Crew: 2

Length: 8.13 m (26 ft 8 in) fuselage only

10.30 m (33 ft 8¾ in) with FD-2 antenna array

Wingspan: 10 m (32 ft 10 in)

Height: 2.95 m (9 ft 8 in)

Wing area: 13.2 m² (142 sq ft)

Empty weight: 2,300 kg (5,071 lb)

Gross weight: 3,500 kg (7,716 lb)

Max takeoff weight: 4,080 kg (8,995 lb)

 

Powerplant:

2× Ishikawajima Ne-130 or Ne-230 axial-flow turbojet engines

each with 8.83 kN/900 kg or 8.68 kN/885 kg thrust

 

Performance:

Maximum speed: 785 km/h (487 mph, 426 kn)

Range: 925 km (574 mi, 502 nmi) with internal fuel

Service ceiling: 12,000 m (39,000 ft)

Rate of climb: 10.5 m/s (2,064 ft/min)

Wing loading: 265 kg/m² (54 lb/sq ft)

Thrust-to-weight ratio: 0.43

 

Armament:

1× 30 mm (1.181 in) Type 5 cannon with 50 rounds in the nose

1× 20 mm (0.787 in) Type Ho-2 cannon with 80 rounds, mounted obliquely behind the cockpit

1× ventral hardpoint for a 500 l drop tank or a single 500 kg (1,102 lb) bomb

  

The kit and its assembly:

This is in fact the second Kikka I have built, and this time it’s a two-seater from AZ Models – actually the trainer boxing, but converted into a personal night fighter interpretation. The AZ Models kit is a simple affair, but that's also its problem. In the box things look quite good, detail level is on par with a classic Matchbox kit. But unlike a Matchbox kit, the AZ Models offering does not go together well. I had to fight everywhere with poor fit, lack of locator pins, ejection marks - anything a short run model kit can throw at you! Thanks to the experience with the single-seater kit some time ago, things did not become too traumatic, but it’s still not a kit for beginners. What worked surprisingly well was the IP canopy, though, which I cut into five sections for an optional open display – even though I am not certain if the kit’s designers had put some brain into their work because the canopy’s segmentation becomes more and more dubious the further you go backwards.

 

The only personal mods is a slightly changed armament, with one nose gun deleted and faired over with a piece of styrene sheet, while the leftover gun was mounted obliquely onto the left flank. I initially considered a position behind the canopy but rejected this because of CoG reasons. Then I planned to mount it directly behind the 2nd seat, so that the barrel would protrude through the canopy, but this appeared unrealistic because the (utterly tiny) sliding canopy for the rear crewman could not have been opened anymore? Finally, I settled for an offset position in the aircraft’s flanks, partly inspired by “Schräge Musik” arrangements on some German Fw 190 night fighters.

 

The antennae come from a Jadar Model PE set for Italeri’s Me 210s, turning it either into a night fighter or a naval surveillance aircraft.

  

Painting and markings:

This became rather lusterless; many late IJN night fighters carried a uniform dark green livery with minimalistic, toned-down markings, e. g. hinomaru without a white high-contrast edge, just the yellow ID bands on the wings’ leading edges were retained.

For this look the model received an overall basis coat of Humbrol 75 (Bronze Green), later treated with a black ink washing, dry-brushed aluminum and post-shading with lighter shades of dark green (including Humbrol 116 and Revell 67). The only colorful highlight is a red fin tip (Humbrol 19) and a thin red stripe underneath (decal). The yellow and white ID bands were created with decal material.

 

The cockpit interior was painted in a yellowish-green primer (trying to simulate a typical “bamboo” shade that was used in some late-war IJN cockpits), while the landing gear wells were painted in aodake iro, a clear bluish protective lacquer. The landing gear struts themselves became semi-matt black.

 

The markings are fictional and were puzzled together from various sources. The hinomaru came from the AZ Models’ Kikka single seater sheet (since it offers six roundels w/o white edge), the tactical code on the fin was created with red numbers from a Fujimi Aichi B7A2 Ryusei.

 

Finally, the kit received a coat of matt acrylic varnish and some grinded graphite around the jet exhausts and the gun nozzles.

  

Well, this fictional Kikka night fighter looks quite dry, but that makes it IMHO more credible. The large antler antenna array might look “a bit too much”, and a real night fighter probably had a simpler arrangement with a single Yagi-style/arrow-shaped antenna, but a description of the FD-2 radar suggested the layout I chose – and it does not look bad. The oblique cannon in the flank is another odd detail, but it is not unplausible. However, with all the equipment and esp. the draggy antennae on board, the Kikka’s mediocre performance would surely have seriously suffered, probably beyond an effective use. But this is whifworld, after all. ;-)

I've posted a blurry version of the same crowd a few weeks ago. Female teenagers waiting for a Tokio Hotel concert in Paris. All female teenagers but three mothers and one boy.

 

Marketing segmentation ?

Harris's hawk (Parabuteo unicinctus), formerly known as the bay-winged hawk, dusky hawk, and sometimes a wolf hawk, and known in Latin America as peuco, is a medium-large bird of prey that breeds from the southwestern United States south to Chile, central Argentina, and Brazil. This bird is sometimes reported to be at large in Western Europe, especially Britain, but it is a popular species in falconry and these records almost invariably all refer to escapes from captivity.

 

The name is derived from the Greek para, meaning beside, near or like, and the Latin buteo, referring to a kind of buzzard; uni meaning once; and cinctus meaning girdled, referring to the white band at the tip of the tail. John James Audubon gave this bird its English name in honor of his ornithological companion, financial supporter, and friend Edward Harris.

 

Harris's hawk is notable for its behavior of hunting cooperatively in packs consisting of tolerant groups, while other raptors often hunt alone. Harris hawks' social nature has been attributed to their intelligence, which makes them easy to train and has made them a popular bird for use in falconry.

 

Description

This medium-large hawk is roughly intermediate in size between a peregrine falcon (Falco peregrinus) and a red-tailed hawk (Buteo jamaicensis). Harris's hawks range in length from 46 to 59 cm (18 to 23 in) and generally have a wingspan of about 103 to 120 cm (41 to 47 in). These hawks have a brownish plumage, reddish shoulders, and tail feathers with a white base and white tip.

 

They exhibit sexual dimorphism with the females being larger by about 35%. In the United States, the average weight for adult males is about 701 g (1.545 lb), with a range of 546 to 850 g (1.204 to 1.874 lb), while the adult female average is 1,029 g (2.269 lb), with a range of 766 to 1,633 g (1.689 to 3.600 lb). They have dark brown plumage with chestnut shoulders, wing linings, and thighs, white on the base and tip of the tail, long, yellow legs, and a yellow cere. The vocalizations of Harris's hawk are very harsh sounds.

 

The lifespan of Harris's Hawk is 10–12 years in the wild and 20–25 years in captivity.

 

Juvenile

The juvenile Harris's hawk is mostly streaked with buff and appears much lighter than the dark adults. When in flight, the undersides of the juveniles' wings are buff-colored with brown streaking. They can look unlike adults at first glance, but the identical chestnut plumage is an aid for identification.

 

Subspecies

P. u. superior: found in Baja California, Arizona, Sonora, and Sinaloa. P. u. superior was believed to have longer tails and wings and to be more blackish than P. u. harrisi. However, the sample size of the original study was quite small, with only five males and six females. Later research has concluded that there is not as strong a physical difference as was originally assumed. Other ecological differences, such as latitudinal cline were also brought up as arguments against the validity of the subspecies segmentation.

P. u. harrisi: found in Texas, eastern Mexico, and much of Central America.

P. u. unicinctus: found exclusively in South America. It is smaller than the North American subspecies and the adult's dark brown ventrum is streaked or flecked with white or whitish.

Taxonomy

Robert Ridgway placed Harris' Hawk in its own new subgenus Urubitinga (Antenor) in 1873, and introduced the generic name Parabuteo in 1874. Richard Bowdler Sharpe also separated Harris' Hawk to a monotypic genus, Erythrocnema, in 1874. In his Catalogue of Birds in the British Museum, Sharpe gives an extensive synonymy, with various authors having earlier placed harrisii in three genera and unicinctus in eleven.

 

Distribution and habitat

Harris's hawks live in sparse woodland and semi-desert, as well as marshes (with some trees) in some parts of their range (Howell and Webb 1995), including mangrove swamps, as in parts of their South American range. Harris's hawks are permanent residents and do not migrate. Important perches and nest supports are provided by scattered larger trees or other features (e.g., power poles, woodland edges, standing dead trees, live trees, boulders, and saguaros).

 

The wild Harris's hawk population is declining due to habitat loss; however, under some circumstances, they have been known to move into developed areas.

 

Behaviour

This species occurs in relatively stable groups. A dominance hierarchy occurs in Harris's hawks, wherein the mature female is the dominant bird, followed by the adult male and then the young of previous years. Groups typically include from two to seven birds. Not only do birds cooperate in hunting, but they also assist in the nesting process. No other bird of prey is known to hunt in groups as routinely as this species.

 

Breeding

They nest in small trees, shrubby growth, or cacti. The nests are often compact, made of sticks, plant roots, and stems and are often lined with leaves, moss, bark, and plant roots. They are built mainly by the female. There are usually two to four white to blueish-white eggs sometimes with a speckling of pale brown or gray. The nestlings start light buff, but in five to six days turn a rich brown.

 

Very often, there will be three hawks attending one nest: two males and one female. Whether or not this is polyandry is debated, as it may be confused with backstanding (one bird standing on another's back). The female does most of the incubation. The eggs hatch in 31 to 36 days. The young begin to explore outside the nest at 38 days, and fledge, or start to fly, at 45 to 50 days. The female sometimes breeds two or three times in a year. Young may stay with their parents for up to three years, helping to raise later broods. Nests are known to be predated by coyotes (Canis latrans), golden eagles (Aquila chrysaetos), red-tailed hawks (Buteo jamaicensis), great horned owls (Bubo virginianus), and flocks of common ravens (Corvus corax), predators possibly too formidable to be fully displaced by Harris's hawk's cooperative nest defenses. No accounts show predation on adults in the United States and Harris's hawk may be considered an apex predator, although presumably predators like eagles and great horned owls would be capable of killing them. In Chile, black-chested buzzard-eagles (Geranoaetus melanoleucus) are likely predators.

 

Feeding

The majority of Harris hawk's prey are mammals, including ground squirrels, rabbits, and larger black-tailed jackrabbits (Lepus californicus). Birds from the size of small passerines such as diuca finch (Diuca diuca) to adult great egret (Ardea alba) and half-grown wild turkey (Meleagris gallapavo) can be taken. In one instance, the lone Harris hawk successfully killed a subadult great blue heron (Ardea herodias). Reptiles such as lizards and snakes are additionally taken as well as large insects.

 

When hunting in groups, Harris's hawk can take large prey effectively, such as desert cottontail (Syvilagus auduboni), the leading prey species in the north of Harris's hawk's range, usually weighs 800 g (1.8 lb) or less. Even adult black-tailed jackrabbits weighing more than 2,000 g (4.4 lb) can be successfully taken by a pack of harris hawks.

 

Undoubtedly because it pursues large prey often, this hawk has larger and stronger feet, with long talons, and a larger, more prominent hooked beak than most other raptors around its size. Locally, other buteonine hawks, including the ferruginous hawk, the red-tailed hawk, and the white-tailed hawk also hunt primarily cottontails and jackrabbits, but each is bigger, weighing about 500 g (18 oz), 300 g (11 oz) and 200 g (7.1 oz), respectively, more on average than a Harris's hawk.

 

In the Southwestern United States, the most common prey species (in descending order of prevalence) are desert cottontail (Syvilagus auduboni), eastern cottontail (Syvilagus floridanus), black-tailed jackrabbit (Lepus californicus), ground squirrels (Ammopsermophilus spp. and Spermophilus spp.), woodrats (Neotoma spp.), kangaroo rats (Dipodomys spp.), pocket gophers (Geomys and Thomomys spp.), Gambel's quail (Callipepla gambelii), scaled quail (C. squamata), northern bobwhite (Colinus virginianus), cactus wren (Campylorhynchus brunneicapillus), northern mockingbird (Mimus polyglottos), desert spiny lizards (Sceloporus magister), and skinks (Eumeces spp.) In the tropics, Harris's hawks have adapted to taking prey of several varieties, including those like chickens and European rabbits introduced by man. In Chile, the common degu (Octodon degus) makes up 67.5% of the prey.

 

Hunting

While most raptors are solitary, only coming together for breeding and migration, Harris's hawks will hunt in cooperative groups of two to six. This is believed to be an adaptation to the lack of prey in the desert climate in which they live. In one hunting technique, a small group flies ahead and scouts, then another group member flies ahead and scouts, and this continues until prey is bagged and shared. In another, all the hawks spread around the prey and one bird flushes it out. Harris's hawks will often chase prey on foot, and are quite fast on the ground and their long, yellow legs are adapted for this, as most hawks do not spend as much time on the ground. Groups of Harris's hawks tend to be more successful at capturing prey than lone hawks, with groups of two to four individuals having ~10% higher success rates per extra individual.

 

Relationship with humans

Falconry

Since about 1980, Harris's hawks have been increasingly used in falconry and are now the most popular hawks in the West (outside of Asia) for that purpose, as they are one of the easiest to train and the most social.

 

Trained Harris's hawks have been used to remove an unwanted pigeon population from London's Trafalgar Square, and from the tennis courts at Wimbledon.

 

Trained Harris's hawks have been used for bird abatement by falconry experts in Canada and the United States at various locations including airports, resorts, landfill sites, and industrial sites.

 

In art

John James Audubon illustrated Harris's hawk in The Birds of America (published in London, 1827–38) as Plate 392 with the title "Louisiana Hawk -Buteo harrisi". The image was engraved and colored by the Robert Havell, London workshops in 1837. The original watercolor by Audubon was purchased by the New York History Society where it remains to this day (January 2009).

I just got back from the Churchill Club’s 13th Annual Top 10 Tech Trends Debate (site).

 

Curt Carlson, CEO of SRI, presented their trends from the podium, which are meant to be “provocative, plausible, debatable, and that it will be clear within the next 1-3 years whether or not they will actually become trends.”

 

Then the panelists debated them. Speaking is Aneesh Chopra, CTO of the U.S., and smirking to his left is Paul Saffo, and then Ajay Senkut from Clarium, then me.

 

Here are SRI’s 2011 Top 10 Tech Trends [and my votes]:

 

Trend 1. Age Before Beauty. Technology is designed for—and disproportionately used by—the young. But the young are getting fewer. The big market will be older people. The aging generation has grown up with, and is comfortable with, most technology—but not with today’s latest technology products. Technology product designers will discover the Baby Boomer’s technology comfort zone and will leverage it in the design of new devices. One example today is the Jitterbug cell phone with a large keypad for easy dialing and powerful speakers for clear sound. The trend is for Baby Boomers to dictate the technology products of the future.

 

[I voted YES, it’s an important and underserved market, but for tech products, they are not the early adopters. The key issue is age-inspired entrepreneurship. How can we get the entrepreneurial mind focused on this important market?]

 

Trend 2. The Doctor Is In. Some of our political leaders say that we have "the best medical care system in the world". Think what it must be like in the rest of the world! There are many problems, but one is the high cost of delivering expert advice. With the development of practical virtual personal assistants, powered by artificial intelligence and pervasive low-cost sensors, “the doctor will be in”—online—for people around the world. Instead of the current Web paradigm: “fill out this form, and we’ll show you information about what might be ailing you”, this will be true diagnosis—supporting, and in some cases replacing—human medical practitioners. We were sending X-rays to India to be read; now India is connecting to doctors here for diagnosis in India. We see the idea in websites that now offer online videoconference interaction with a doctor. The next step is automation. The trend is toward complete automation: a combination of artificial intelligence, the Internet, and very low-cost medical instrumentation to provide high-quality diagnostics and advice—including answering patient questions—online to a worldwide audience.

 

[NO. Most doctor check-ups and diagnoses will still need to be conducted in-person (blood tests, physical exams, etc). Sensor technology can’t completely replace human medical practitioners in the near future. Once we have the physical interface (people for now), then the networking and AI capabilities can engage, bringing specialist reactions to locally collected data. The real near-term trend in point-of-care is the adoption of iPads/phones connected to cloud services like ePocrates and Athenahealth and soon EMRs.]

    

Trend 3. Made for Me. Manufacturing is undergoing a revolution. It is becoming technically and economically possible to create products that are unique to the specific needs of individuals. For example, a cell phone that has only the hardware you need to support the features you want—making it lighter, thinner, more efficient, much cheaper, and easier to use. This level of customization is being made possible by converging technical advances: new 3D printing technology is well documented, and networked micro-robotics is following. 3D printing now includes applications in jewelry, industrial design, and dentistry. While all of us may not be good product designers, we have different needs, and we know what we want. The trend is toward practical, one-off production of physical goods in widely distributed micro-factories: the ultimate customization of products. The trend is toward practical, one-off production of physical goods in widely distributed micro-factories: the ultimate customization of products.

 

[NO. Personalization is happening just fine at the software level. The UI skins and app code is changeable at zero incremental cost. Code permeates outward into the various vessels we build for it. The iPhone. Soon, the car (e.g. Tesla Sedan). Even the electrical circuits (when using an FPGA). This will extend naturally to biological code, with DNA synthesis costs plummeting (but that will likely stay centralized in BioFabs for the next 3 years. When it comes to building custom physical things, the cost and design challenges relegate it to prototyping, tinkering and hacks. Too many people have a difficult time in 3D content creation. The problem is the 2D interfaces of mouse and screen. Perhaps a multitouch interface to digital clay could help, where the polygons snap to fit after the form is molded by hand.]

     

Trend 4. Pay Me Now. Information about our personal behavior and characteristics is exploited regularly for commercial purposes, often returning little or no value to us, and sometimes without our knowledge. This knowledge is becoming a key asset and a major competitive advantage for the companies that gather it. Think of your supermarket club card. These knowledge-gatherers will need to get smarter and more aggressive in convincing us to share our information with them and not with their competitors. If TV advertisers could know who the viewers are, the value of the commercials would go up enormously. The trend is technology and business models based on attracting consumers to share large amounts of information exclusively with service providers.

 

[YES, but it’s nothing new. Amazon makes more on merchandising than product sales margin. And, certain companies are getting better and better at acquiring customer information and personalizing offerings specifically to these customers. RichRelevance provides this for ecommerce (driving 25% of all e-commerce on Black Friday). Across all those vendors, the average lift from personalizing the shopping experience: 15% increase in overall sales and 8% increase in long-term profitability. But, simply being explicit and transparent to the consumer about the source of the data can increase the effectiveness of targeted programs by up to 100% (e.g., saying “Because you bought this product and other consumers who bought it also bought this other product" yielded a 100% increase in product recommendation effectiveness in numerous A/B tests). Social graph is incredibly valuable as a marketing tool.]

       

Trend 5. Rosie, At Last. We’ve been waiting a long time for robots to live in and run our homes, like Rosie in the Jetsons’ household. It’s happening a little now: robots are finally starting to leave the manufacturing floor and enter people's homes, offices, and highways. Robots can climb walls, fly, and run. We all know the Roomba for cleaning floors—and now there’s the Verro for your pool. Real-time vision and other sensors, and affordable precise manipulation, are enabling robots to assist in our care, drive our cars, and protect our homes and property. We need to broaden our view of robots and the forms they will take—think of a self-loading robot-compliant dishwasher or a self-protecting house. The trend is robots becoming embedded in our environments, and taking advantage of the cloud, to understand and fulfill our needs.

 

[NO. Not in 3 years. Wanting it badly does not make it so. But I just love that Google RoboCar. Robots are not leaving the factory floor – that’s where the opportunity for newer robots and even humanoid robots will begin. There is plenty of factory work still to be automated. Rodney Brooks of MIT thinks they can be cheaper than the cheapest outsourced labor. So the robots are coming, to the factory and the roads to start, and then the home.]

  

Trend 6. Social, Really. The rise of social networks is well documented, but they're not really social networks. They're a mix of friends, strangers, organizations, hucksters—it’s more like walking through a rowdy crowd in Times Square at night with a group of friends. There is a growing need for social networks that reflect the fundamental nature of human relationships: known identities, mutual trust, controlled levels of intimacy, and boundaries of shared information. The trend is the rise of true social networks, designed to maintain real, respectful relationships online.

  

[YES. The ambient intimacy of Facebook is leading to some startling statistics on fB evidence reuse by divorce lawyers (80%) and employment rejections (70%). There are differing approaches to solve this problem: Altly’s alternative networks with partioning and control, Jildy’s better filtering and auto-segmentation, and Path’s 50 friend limit.]

  

Trend 7. In-Your-Face Augmented Reality. With ever-cheaper computation and advances in computer vision technology, augmented reality is becoming practical, even in mobile devices. We will move beyond expensive telepresence environments and virtual reality games to fully immersive environments—in the office, on the factory floor, in medical care facilities, and in new entertainment venues. I once did an experiment where a person came into a room and sat down at a desk against a large, 3D, high-definition TV display. The projected image showed a room with a similar desk up against the screen. The person would put on 3D glasses, and then a projected person would enter and sit down at the other table. After talking for 5 to 10 minutes, the projected person would stand up and put their hand out. Most of the time, the first person would also stand up and put their hand into the screen—they had quickly adapted and forgotten that the other person was not in the room. Augmented reality will become indistinguishable from reality. The trend is an enchanted world— The trend is hyper-resolution augmented reality and hyper-accurate artificial people and objects that fundamentally enhance people's experience of the world.

 

[NO, lenticular screens are too expensive and 3D glasses are a pain in the cortex. Augmented reality with iPhones is great, and pragmatic, but not a top 10 trend IMHO]

   

Trend 8. Engineering by Biologists.

Biologists and engineers are different kinds of people—unless they are working on synthetic biology. We know about genetically engineered foods and creatures, such as gold fish in multiple other colors. Next we’ll have biologically engineered circuits and devices. Evolution has created adaptive processing and system resiliency that is much more advanced than anything we’ve been able to design. We are learning how to tap into that natural expertise, designing devices using the mechanisms of biology. We have already seen simple biological circuits in the laboratory. The trend is practical, engineered artifacts, devices, and computers based on biology rather than just on silicon.

 

[YES, and NO because it was so badly mangled as a trend. For the next few years, these approaches will be used for fuels and chemicals and materials processing because they lend themselves to a 3D fluid medium. Then 2D self-assembling monolayers. And eventually chips , starting with memory and sensor arrays long before heterogeneous logic. And processes of biology will be an inspiration throughout (evolution, self-assembly, etc.). Having made predictions along these themes for about a decade now, the wording of this one frustrated me]

 

Trend 9. ‘Tis a Gift to be Simple. Cyber attacks are ever more frequent and effective. Most attacks exploit holes that are inevitable given the complexity of the software products we use every day. Cyber researchers really understand this. To avoid these vulnerabilities, some cyber researchers are beginning to use only simple infrastructure and applications that are throwbacks to the computing world of two decades ago. As simplicity is shown to be an effective approach for avoiding attack, it will become the guiding principle of software design. The trend is cyber defense through widespread adoption of simple, low-feature software for consumers and businesses.

 

[No. I understand the advantages of being open, and of heterogencity of code (to avoid monoculture collapse), but we have long ago left the domain of simple. Yes, Internet transport protocols won via simplicity. The presentation layer, not so much. If you want dumb pipes, you need smart edges, and smart edges can be hacked. Graham Spencer gave a great talk at SFI: the trend towards transport simplicity (e.g. dumb pipes) and "intelligence in the edges" led to mixing code and data, which in turn led to all kinds of XSS-like attacks. Drive-by downloading (enabled by XSS) is the most popular vehicle for delivering malware these days.]

 

Trend 10. Reverse Innovation. Mobile communication is proliferating at an astonishing rate in developing countries as price-points drop and wireless infrastructure improves. As developing countries leapfrog the need for physical infrastructure and brokers, using mobile apps to conduct micro-scale business and to improve quality of life, they are innovating new applications. The developing world is quickly becoming the largest market we’ve ever seen—for mobile computing and much more. The trend is for developing countries to turn around the flow of innovation: Silicon Valley will begin to learn more from them about innovative applications than they need to learn from us about the underlying technology.

 

[YES, globalization is a megatrend still in the making. The mobile markets are clearly China, India and Korea, with app layer innovation increasingly originating there. Not completely of course, but we have a lot to learn from the early-adopter economies.]

 

In watercolour style. Paper from cgtextures.com

Taken at the Show 'N Tell Car Show held in the Reading suburb of Cincinnati, Ohio. When I was a kid, my father bought a secondhand LaSalle four door sedan to use as the family car. We didn't have the car long, but I remember it fondly.

 

This LaSalle was thought to be near the top of the line. Only 185 were built in 1939 which represented 1% of LaSalle's production that year. There are only 5 registered remaining ones and probably less than 20 left. It is powered by a 322 cu. in. flat head V8 and has a three speed manual transmission. The rear windscreen is dealer installed. The owner, Greg Thomas, told me that he owns other classic cars, but I can't remember what he told me they are.

 

From Wikipedia:

 

"LaSalle was an American brand of luxury automobiles manufactured and marketed by General Motors' Cadillac division from 1927 through 1940. Alfred P. Sloan developed the concept for LaSalle and certain other General Motors' marques in order to fill pricing gaps he perceived in the General Motors product portfolio. Sloan created LaSalle as a companion marque for Cadillac. LaSalle automobiles were manufactured by Cadillac, but were priced lower than Cadillac-branded automobiles and were marketed as the second-most prestigious marque in the General Motors portfolio.

 

The LaSalle had its beginnings when General Motors' CEO, Alfred P. Sloan, noticed that his carefully crafted market segmentation program was beginning to develop price gaps in which General Motors had no products to sell.[citation needed] In an era where automotive brands were somewhat restricted to building a specific car per model year, Sloan surmised that the best way to bridge the gaps was to develop "companion" marques that could be sold through the current sales network.[citation needed]

As originally developed by Sloan, General Motors' market segmentation strategy placed each of the company's individual automobile marques into specific price points, called the General Motors Companion Make Program. The Chevrolet was designated as the entry level product. Next, (in ascending order), came the Pontiac, Oakland, Oldsmobile, Viking, Marquette, Buick, LaSalle, and ultimately, Cadillac. By the 1920s, certain General Motors products began to shift out of the plan as the products improved and engine advances were made."

Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms. Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. As of November 2015, at least 45,700 spider species, and 114 families have been recorded by taxonomists. However, there has been dissension within the scientific community as to how all these families should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.

 

Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.

 

Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appeared in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets. True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving suborder, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before 200 million years ago.

 

A herbivorous species, Bagheera kiplingi, was described in 2008, but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, and they liquefy their food by flooding it with digestive enzymes and grinding it with the bases of their pedipalps, as they do not have true jaws.

 

Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity.

 

While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers. An abnormal fear of spiders is called arachnophobia.

 

DESCRIPTION

BODY PLAN

Spiders are chelicerates and therefore arthropods. As arthropods they have: segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo.[7] Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the cephalothorax or prosoma, is a complete fusion of the segments that in an insect would form two separate tagmata, the head and thorax; the rear tagma is called the abdomen or opisthosoma. In spiders, the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel. The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods. In fact, chelicerates' only appendages ahead of the mouth are a pair of chelicerae, and they lack anything that would function directly as "jaws". The first appendages behind the mouth are called pedipalps, and serve different functions within different groups of chelicerates.

 

Spiders and scorpions are members of one chelicerate group, the arachnids. Scorpions' chelicerae have three sections and are used in feeding. Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use. The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food. Scorpions' pedipalps generally form large claws for capturing prey, while those of spiders are fairly small appendages whose bases also act as an extension of the mouth; in addition, those of male spiders have enlarged last sections used for sperm transfer.

 

In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk. The upper surface of the cephalothorax is covered by a single, convex carapace, while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface.

 

Like other arthropods, spiders are coelomates in which the coelom is reduced to small areas round the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows. The heart is a tube in the upper part of the body, with a few ostia that act as non-return valves allowing blood to enter the heart from the hemocoel but prevent it from leaving before it reaches the front end. However, in spiders, it occupies only the upper part of the abdomen, and blood is discharged into the hemocoel by one artery that opens at the rear end of the abdomen and by branching arteries that pass through the pedicle and open into several parts of the cephalothorax. Hence spiders have open circulatory systems. The blood of many spiders that have book lungs contains the respiratory pigment hemocyanin to make oxygen transport more efficient.

 

Spiders have developed several different respiratory anatomies, based on book lungs, a tracheal system, or both. Mygalomorph and Mesothelae spiders have two pairs of book lungs filled with haemolymph, where openings on the ventral surface of the abdomen allow air to enter and diffuse oxygen. This is also the case for some basal araneomorph spiders, like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs. The trachea system has most likely evolved in small ancestors to help resist desiccation. The trachea were originally connected to the surroundings through a pair of openings called spiracles, but in the majority of spiders this pair of spiracles has fused into a single one in the middle, and moved backwards close to the spinnerets. Spiders that have tracheae generally have higher metabolic rates and better water conservation. Spiders are ectotherms, so environmental temperatures affect their activity.

 

FEEDING, DIGESTION AND EXCRETION

Uniquely among chelicerates, the final sections of spiders' chelicerae are fangs, and the great majority of spiders can use them to inject venom into prey from venom glands in the roots of the chelicerae. The family Uloboridae has lost its venom glands, and kills its prey with silk instead. Like most arachnids, including scorpions, spiders have a narrow gut that can only cope with liquid food and spiders have two sets of filters to keep solids out. They use one of two different systems of external digestion. Some pump digestive enzymes from the midgut into the prey and then suck the liquified tissues of the prey into the gut, eventually leaving behind the empty husk of the prey. Others grind the prey to pulp using the chelicerae and the bases of the pedipalps, while flooding it with enzymes; in these species, the chelicerae and the bases of the pedipalps form a preoral cavity that holds the food they are processing.

 

The stomach in the cephalothorax acts as a pump that sends the food deeper into the digestive system. The mid gut bears many digestive ceca, compartments with no other exit, that extract nutrients from the food; most are in the abdomen, which is dominated by the digestive system, but a few are found in the cephalothorax.

 

Most spiders convert nitrogenous waste products into uric acid, which can be excreted as a dry material. Malphigian tubules ("little tubes") extract these wastes from the blood in the hemocoel and dump them into the cloacal chamber, from which they are expelled through the anus. Production of uric acid and its removal via Malphigian tubules are a water-conserving feature that has evolved independently in several arthropod lineages that can live far away from water,[14] for example the tubules of insects and arachnids develop from completely different parts of the embryo. However, a few primitive spiders, the sub-order Mesothelae and infra-order Mygalomorphae, retain the ancestral arthropod nephridia ("little kidneys"), which use large amounts of water to excrete nitrogenous waste products as ammonia.

 

CENTRAL NERVOS SYSTEM

The basic arthropod central nervous system consists of a pair of nerve cords running below the gut, with paired ganglia as local control centers in all segments; a brain formed by fusion of the ganglia for the head segments ahead of and behind the mouth, so that the esophagus is encircled by this conglomeration of ganglia. Except for the primitive Mesothelae, of which the Liphistiidae are the sole surviving family, spiders have the much more centralized nervous system that is typical of arachnids: all the ganglia of all segments behind the esophagus are fused, so that the cephalothorax is largely filled with nervous tissue and there are no ganglia in the abdomen; in the Mesothelae, the ganglia of the abdomen and the rear part of the cephalothorax remain unfused.

 

Despite the relatively small central nervous system, some spiders (like Portia) exhibit complex behaviour, including the ability to use a trial-and-error approach.

 

SENSE ORGANS

EYES

Most spiders have four pairs of eyes on the top-front area of the cephalothorax, arranged in patterns that vary from one family to another. The pair at the front are of the type called pigment-cup ocelli ("little eyes"), which in most arthropods are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup. However, the main eyes at the front of spiders' heads are pigment-cup ocelli that are capable of forming images. The other eyes are thought to be derived from the compound eyes of the ancestral chelicerates, but no longer have the separate facets typical of compound eyes. Unlike the main eyes, in many spiders these secondary eyes detect light reflected from a reflective tapetum lucidum, and wolf spiders can be spotted by torch light reflected from the tapeta. On the other hand, jumping spiders' secondary eyes have no tapeta. Some jumping spiders' visual acuity exceeds by a factor of ten that of dragonflies, which have by far the best vision among insects; in fact the human eye is only about five times sharper than a jumping spider's. They achieve this by a telephoto-like series of lenses, a four-layer retina and the ability to swivel their eyes and integrate images from different stages in the scan. The downside is that the scanning and integrating processes are relatively slow.

 

There are spiders with a reduced number of eyes, of these those with six-eyes are the most numerous and are missing a pair of eyes on the anterior median line, others species have four-eyes and some just two. Cave dwelling species have no eyes, or possess vestigial eyes incapable of sight.

 

OTHER SENSES

As with other arthropods, spiders' cuticles would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly bristles called setae, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell, often by means of setae. Pedipalps carry a large number of such setae sensitive to contact chemicals and air-borne smells, such as female pheromones. Spiders also have in the joints of their limbs slit sensillae that detect forces and vibrations. In web-building spiders, all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively.

 

Like most arthropods, spiders lack balance and acceleration sensors and rely on their eyes to tell them which way is up. Arthropods' proprioceptors, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well understood. On the other hand, little is known about what other internal sensors spiders or other arthropods may have.

 

LOCOMOTION

Each of the eight legs of a spider consists of seven distinct parts. The part closest to and attaching the leg to the cephalothorax is the coxa; the next segment is the short trochanter that works as a hinge for the following long segment, the femur; next is the spider's knee, the patella, which acts as the hinge for the tibia; the metatarsus is next, and it connects the tibia to the tarsus (which may be thought of as a foot of sorts); the tarsus ends in a claw made up of either two or three points, depending on the family to which the spider belongs. Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, spiders and a few other groups still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors. The only extensor muscles in spider legs are located in the three hip joints (bordering the coxa and the trochanter). As a result, a spider with a punctured cephalothorax cannot extend its legs, and the legs of dead spiders curl up. Spiders can generate pressures up to eight times their resting level to extend their legs, and jumping spiders can jump up to 50 times their own length by suddenly increasing the blood pressure in the third or fourth pair of legs. Although larger spiders use hydraulics to straighten their legs, unlike smaller jumping spiders they depend on their flexor muscles to generate the propulsive force for their jumps.

 

Most spiders that hunt actively, rather than relying on webs, have dense tufts of fine hairs between the paired claws at the tips of their legs. These tufts, known as scopulae, consist of bristles whose ends are split into as many as 1,000 branches, and enable spiders with scopulae to walk up vertical glass and upside down on ceilings. It appears that scopulae get their grip from contact with extremely thin layers of water on surfaces. Spiders, like most other arachnids, keep at least four legs on the surface while walking or running.

 

SILK PRODUCTION

The abdomen has no appendages except those that have been modified to form one to four (usually three) pairs of short, movable spinnerets, which emit silk. Each spinneret has many spigots, each of which is connected to one silk gland. There are at least six types of silk gland, each producing a different type of silk.

 

Silk is mainly composed of a protein very similar to that used in insect silk. It is initially a liquid, and hardens not by exposure to air but as a result of being drawn out, which changes the internal structure of the protein. It is similar in tensile strength to nylon and biological materials such as chitin, collagen and cellulose, but is much more elastic. In other words, it can stretch much further before breaking or losing shape.

 

Some spiders have a cribellum, a modified spinneret with up to 40,000 spigots, each of which produces a single very fine fiber. The fibers are pulled out by the calamistrum, a comb-like set of bristles on the jointed tip of the cribellum, and combined into a composite woolly thread that is very effective in snagging the bristles of insects. The earliest spiders had cribella, which produced the first silk capable of capturing insects, before spiders developed silk coated with sticky droplets. However, most modern groups of spiders have lost the cribellum.

 

Tarantulas also have silk glands in their feet.

 

Even species that do not build webs to catch prey use silk in several ways: as wrappers for sperm and for fertilized eggs; as a "safety rope"; for nest-building; and as "parachutes" by the young of some species.

 

REPRODUCTION AND LIFE CYCLE

Spiders reproduce sexually and fertilization is internal but indirect, in other words the sperm is not inserted into the female's body by the male's genitals but by an intermediate stage. Unlike many land-living arthropods, male spiders do not produce ready-made spermatophores (packages of sperm), but spin small sperm webs on to which they ejaculate and then transfer the sperm to special syringe-like structures, palpal bulbs or palpal organs, borne on the tips of the pedipalps of mature males. When a male detects signs of a female nearby he checks whether she is of the same species and whether she is ready to mate; for example in species that produce webs or "safety ropes", the male can identify the species and sex of these objects by "smell".

 

Spiders generally use elaborate courtship rituals to prevent the large females from eating the small males before fertilization, except where the male is so much smaller that he is not worth eating. In web-weaving species, precise patterns of vibrations in the web are a major part of the rituals, while patterns of touches on the female's body are important in many spiders that hunt actively, and may "hypnotize" the female. Gestures and dances by the male are important for jumping spiders, which have excellent eyesight. If courtship is successful, the male injects his sperm from the palpal bulbs into the female's genital opening, known as the epigyne, on the underside of her abdomen. Female's reproductive tracts vary from simple tubes to systems that include seminal receptacles in which females store sperm and release it when they are ready.

 

Males of the genus Tidarren amputate one of their palps before maturation and enter adult life with one palp only. The palps are 20% of male's body mass in this species, and detaching one of the two improves mobility. In the Yemeni species Tidarren argo, the remaining palp is then torn off by the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime, the female feeds on the palpless male. In over 60% of cases, the female of the Australian redback spider kills and eats the male after it inserts its second palp into the female's genital opening; in fact, the males co-operate by trying to impale themselves on the females' fangs. Observation shows that most male redbacks never get an opportunity to mate, and the "lucky" ones increase the likely number of offspring by ensuring that the females are well-fed. However, males of most species survive a few matings, limited mainly by their short life spans. Some even live for a while in their mates' webs.

 

Females lay up to 3,000 eggs in one or more silk egg sacs, which maintain a fairly constant humidity level. In some species, the females die afterwards, but females of other species protect the sacs by attaching them to their webs, hiding them in nests, carrying them in the chelicerae or attaching them to the spinnerets and dragging them along.

 

Baby spiders pass all their larval stages inside the egg and hatch as spiderlings, very small and sexually immature but similar in shape to adults. Some spiders care for their young, for example a wolf spider's brood cling to rough bristles on the mother's back, and females of some species respond to the "begging" behaviour of their young by giving them their prey, provided it is no longer struggling, or even regurgitate food.

 

Like other arthropods, spiders have to molt to grow as their cuticle ("skin") cannot stretch. In some species males mate with newly molted females, which are too weak to be dangerous to the males. Most spiders live for only one to two years, although some tarantulas can live in captivity for over 20 years.

 

SIZE

Spiders occur in a large range of sizes. The smallest, Patu digua from Colombia, are less than 0.37 mm in body length. The largest and heaviest spiders occur among tarantulas, which can have body lengths up to 90 mm and leg spans up to 250 mm.

 

ECOLOGY AND BEHAVIOR

NON-PREDATORY FEEDING

Although spiders are generally regarded as predatory, the jumping spider Bagheera kiplingi gets over 90% of its food from fairly solid plant material produced by acacias as part of a mutually beneficial relationship with a species of ant.

 

Juveniles of some spiders in the families Anyphaenidae, Corinnidae, Clubionidae, Thomisidae and Salticidae feed on plant nectar. Laboratory studies show that they do so deliberately and over extended periods, and periodically clean themselves while feeding. These spiders also prefer sugar solutions to plain water, which indicates that they are seeking nutrients. Since many spiders are nocturnal, the extent of nectar consumption by spiders may have been underestimated. Nectar contains amino acids, lipids, vitamins and minerals in addition to sugars, and studies have shown that other spider species live longer when nectar is available. Feeding on nectar avoids the risks of struggles with prey, and the costs of producing venom and digestive enzymes.

 

Various species are known to feed on dead arthropods (scavenging), web silk, and their own shed exoskeletons. Pollen caught in webs may also be eaten, and studies have shown that young spiders have a better chance of survival if they have the opportunity to eat pollen. In captivity, several spider species are also known to feed on bananas, marmalade, milk, egg yolk and sausages.

 

METHODS OF CAPTURING PREY

The best-known method of prey capture is by means of sticky webs. Varying placement of webs allows different species of spider to trap different insects in the same area, for example flat horizontal webs trap insects that fly up from vegetation underneath while flat vertical webs trap insects in horizontal flight. Web-building spiders have poor vision, but are extremely sensitive to vibrations.

 

Females of the water spider Argyroneta aquatica build underwater "diving bell" webs that they fill with air and use for digesting prey, molting, mating and raising offspring. They live almost entirely within the bells, darting out to catch prey animals that touch the bell or the threads that anchor it. A few spiders use the surfaces of lakes and ponds as "webs", detecting trapped insects by the vibrations that these cause while struggling.

 

Net-casting spiders weave only small webs, but then manipulate them to trap prey. Those of the genus Hyptiotes and the family Theridiosomatidae stretch their webs and then release them when prey strike them, but do not actively move their webs. Those of the family Deinopidae weave even smaller webs, hold them outstretched between their first two pairs of legs, and lunge and push the webs as much as twice their own body length to trap prey, and this move may increase the webs' area by a factor of up to ten. Experiments have shown that Deinopis spinosus has two different techniques for trapping prey: backwards strikes to catch flying insects, whose vibrations it detects; and forward strikes to catch ground-walking prey that it sees. These two techniques have also been observed in other deinopids. Walking insects form most of the prey of most deinopids, but one population of Deinopis subrufa appears to live mainly on tipulid flies that they catch with the backwards strike.

 

Mature female bolas spiders of the genus Mastophora build "webs" that consist of only a single "trapeze line", which they patrol. They also construct a bolas made of a single thread, tipped with a large ball of very wet sticky silk. They emit chemicals that resemble the pheromones of moths, and then swing the bolas at the moths. Although they miss on about 50% of strikes, they catch about the same weight of insects per night as web-weaving spiders of similar size. The spiders eat the bolas if they have not made a kill in about 30 minutes, rest for a while, and then make new bolas. Juveniles and adult males are much smaller and do not make bolas. Instead they release different pheromones that attract moth flies, and catch them with their front pairs of legs.

 

The primitive Liphistiidae, the "trapdoor spiders" of the family Ctenizidae and many tarantulas are ambush predators that lurk in burrows, often closed by trapdoors and often surrounded by networks of silk threads that alert these spiders to the presence of prey. Other ambush predators do without such aids, including many crab spiders, and a few species that prey on bees, which see ultraviolet, can adjust their ultraviolet reflectance to match the flowers in which they are lurking. Wolf spiders, jumping spiders, fishing spiders and some crab spiders capture prey by chasing it, and rely mainly on vision to locate prey.Some jumping spiders of the genus Portia hunt other spiders in ways that seem intelligent, outflanking their victims or luring them from their webs. Laboratory studies show that Portia's instinctive tactics are only starting points for a trial-and-error approach from which these spiders learn very quickly how to overcome new prey species. However, they seem to be relatively slow "thinkers", which is not surprising, as their brains are vastly smaller than those of mammalian predators.

 

Ant-mimicking spiders face several challenges: they generally develop slimmer abdomens and false "waists" in the cephalothorax to mimic the three distinct regions (tagmata) of an ant's body; they wave the first pair of legs in front of their heads to mimic antennae, which spiders lack, and to conceal the fact that they have eight legs rather than six; they develop large color patches round one pair of eyes to disguise the fact that they generally have eight simple eyes, while ants have two compound eyes; they cover their bodies with reflective hairs to resemble the shiny bodies of ants. In some spider species, males and females mimic different ant species, as female spiders are usually much larger than males. Ant-mimicking spiders also modify their behavior to resemble that of the target species of ant; for example, many adopt a zig-zag pattern of movement, ant-mimicking jumping spiders avoid jumping, and spiders of the genus Synemosyna walk on the outer edges of leaves in the same way as Pseudomyrmex. Ant-mimicry in many spiders and other arthropods may be for protection from predators that hunt by sight, including birds, lizards and spiders. However, several ant-mimicking spiders prey either on ants or on the ants' "livestock", such as aphids. When at rest, the ant-mimicking crab spider Amyciaea does not closely resemble Oecophylla, but while hunting it imitates the behavior of a dying ant to attract worker ants. After a kill, some ant-mimicking spiders hold their victims between themselves and large groups of ants to avoid being attacked.

 

DEFENSE

There is strong evidence that spiders' coloration is camouflage that helps them to evade their major predators, birds and parasitic wasps, both of which have good color vision. Many spider species are colored so as to merge with their most common backgrounds, and some have disruptive coloration, stripes and blotches that break up their outlines. In a few species, such as the Hawaiian happy-face spider, Theridion grallator, several coloration schemes are present in a ratio that appears to remain constant, and this may make it more difficult for predators to recognize the species. Most spiders are insufficiently dangerous or unpleasant-tasting for warning coloration to offer much benefit. However, a few species with powerful venoms, large jaws or irritant hairs have patches of warning colors, and some actively display these colors when threatened.

 

Many of the family Theraphosidae, which includes tarantulas and baboon spiders, have urticating hairs on their abdomens and use their legs to flick them at attackers. These hairs are fine setae (bristles) with fragile bases and a row of barbs on the tip. The barbs cause intense irritation but there is no evidence that they carry any kind of venom. A few defend themselves against wasps by including networks of very robust threads in their webs, giving the spider time to flee while the wasps are struggling with the obstacles. The golden wheeling spider, Carparachne aureoflava, of the Namibian desert escapes parasitic wasps by flipping onto its side and cartwheeling down sand dunes.

 

SOZIAL SPIDERS

A few spider species that build webs live together in large colonies and show social behavior, although not as complex as in social insects. Anelosimus eximius (in the family Theridiidae) can form colonies of up to 50,000 individuals. The genus Anelosimus has a strong tendency towards sociality: all known American species are social, and species in Madagascar are at least somewhat social. Members of other species in the same family but several different genera have independently developed social behavior. For example, although Theridion nigroannulatum belongs to a genus with no other social species, T. nigroannulatum build colonies that may contain several thousand individuals that co-operate in prey capture and share food. Other communal spiders include several Philoponella species (family Uloboridae), Agelena consociata (family Agelenidae) and Mallos gregalis (family Dictynidae). Social predatory spiders need to defend their prey against kleptoparasites ("thieves"), and larger colonies are more successful in this. The herbivorous spider Bagheera kiplingi lives in small colonies which help to protect eggs and spiderlings. Even widow spiders (genus Latrodectus), which are notoriously cannibalistic, have formed small colonies in captivity, sharing webs and feeding together.

 

WEB TYPES

There is no consistent relationship between the classification of spiders and the types of web they build: species in the same genus may build very similar or significantly different webs. Nor is there much correspondence between spiders' classification and the chemical composition of their silks. Convergent evolution in web construction, in other words use of similar techniques by remotely related species, is rampant. Orb web designs and the spinning behaviors that produce them are the best understood. The basic radial-then-spiral sequence visible in orb webs and the sense of direction required to build them may have been inherited from the common ancestors of most spider groups. However, the majority of spiders build non-orb webs. It used to be thought that the sticky orb web was an evolutionary innovation resulting in the diversification of the Orbiculariae. Now, however, it appears that non-orb spiders are a sub-group that evolved from orb-web spiders, and non-orb spiders have over 40% more species and are four times as abundant as orb-web spiders. Their greater success may be because sphecid wasps, which are often the dominant predators of spiders, much prefer to attack spiders that have flat webs.

 

ORB WEBS

About half the potential prey that hit orb webs escape. A web has to perform three functions: intercepting the prey (intersection), absorbing its momentum without breaking (stopping), and trapping the prey by entangling it or sticking to it (retention). No single design is best for all prey. For example: wider spacing of lines will increase the web's area and hence its ability to intercept prey, but reduce its stopping power and retention; closer spacing, larger sticky droplets and thicker lines would improve retention, but would make it easier for potential prey to see and avoid the web, at least during the day. However, there are no consistent differences between orb webs built for use during the day and those built for use at night. In fact, there is no simple relationship between orb web design features and the prey they capture, as each orb-weaving species takes a wide range of prey.

 

The hubs of orb webs, where the spiders lurk, are usually above the center, as the spiders can move downwards faster than upwards. If there is an obvious direction in which the spider can retreat to avoid its own predators, the hub is usually offset towards that direction.

 

Horizontal orb webs are fairly common, despite being less effective at intercepting and retaining prey and more vulnerable to damage by rain and falling debris. Various researchers have suggested that horizontal webs offer compensating advantages, such as reduced vulnerability to wind damage; reduced visibility to prey flying upwards, because of the back-lighting from the sky; enabling oscillations to catch insects in slow horizontal flight. However, there is no single explanation for the common use of horizontal orb webs.

 

Spiders often attach highly visible silk bands, called decorations or stabilimenta, to their webs. Field research suggests that webs with more decorative bands captured more prey per hour. However, a laboratory study showed that spiders reduce the building of these decorations if they sense the presence of predators.

 

In 1973, Skylab 3 took two orb-web spiders into space to test their web-spinning capabilities in zero gravity. At first, both produced rather sloppy webs, but they adapted quickly.

Tangleweb spiders (cobweb spiders)

 

Members of the family Theridiidae weave irregular, tangled, three-dimensional webs, popularly known as cobwebs. There seems to be an evolutionary trend towards a reduction in the amount of sticky silk used, leading to its total absence in some species. The construction of cobwebs is less stereotyped than that of orb-webs, and may take several days.

 

OTHER TYPES OF WEBS

The Linyphiidae generally make horizontal but uneven sheets, with tangles of stopping threads above. Insects that hit the stopping threads fall onto the sheet or are shaken onto it by the spider, and are held by sticky threads on the sheet until the spider can attack from below.

 

EVOLUTION

FOSSIL RECORD

Although the fossil record of spiders is considered poor, almost 1000 species have been described from fossils. Because spiders' bodies are quite soft, the vast majority of fossil spiders have been found preserved in amber. The oldest known amber that contains fossil arthropods dates from 130 million years ago in the Early Cretaceous period. In addition to preserving spiders' anatomy in very fine detail, pieces of amber show spiders mating, killing prey, producing silk and possibly caring for their young. In a few cases, amber has preserved spiders' egg sacs and webs, occasionally with prey attached; the oldest fossil web found so far is 100 million years old. Earlier spider fossils come from a few lagerstätten, places where conditions were exceptionally suited to preserving fairly soft tissues.

 

The oldest known exclusively terrestrial arachnid is the trigonotarbid Palaeotarbus jerami, from about 420 million years ago in the Silurian period, and had a triangular cephalothorax and segmented abdomen, as well as eight legs and a pair of pedipalps. Attercopus fimbriunguis, from 386 million years ago in the Devonian period, bears the earliest known silk-producing spigots, and was therefore hailed as a spider at the time of its discovery. However, these spigots may have been mounted on the underside of the abdomen rather than on spinnerets, which are modified appendages and whose mobility is important in the building of webs. Hence Attercopus and the similar Permian arachnid Permarachne may not have been true spiders, and probably used silk for lining nests or producing egg-cases rather than for building webs. The largest known fossil spider as of 2011 is the araneid Nephila jurassica, from about 165 million years ago, recorded from Daohuogo, Inner Mongolia in China. Its body length is almost 25 mm.

 

Several Carboniferous spiders were members of the Mesothelae, a primitive group now represented only by the Liphistiidae. The mesothelid Paleothele montceauensis, from the Late Carboniferous over 299 million years ago, had five spinnerets. Although the Permian period 299 to 251 million years ago saw rapid diversification of flying insects, there are very few fossil spiders from this period.

 

The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the Triassic well before 200 million years ago. Some Triassic mygalomorphs appear to be members of the family Hexathelidae, whose modern members include the notorious Sydney funnel-web spider, and their spinnerets appear adapted for building funnel-shaped webs to catch jumping insects. Araneomorphae account for the great majority of modern spiders, including those that weave the familiar orb-shaped webs. The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families.

 

FAMILY TREE

It is now agreed that spiders (Araneae) are monophyletic (i.e., members of a group of organisms that form a clade, consisting of a last common ancestor and all of its descendants). There has been debate about what their closest evolutionary relatives are, and how all of these evolved from the ancestral chelicerates, which were marine animals. The cladogram on the right is based on J. W. Shultz' analysis (2007). Other views include proposals that: scorpions are more closely related to the extinct marine scorpion-like eurypterids than to spiders; spiders and Amblypygi are a monophyletic group. The appearance of several multi-way branchings in the tree on the right shows that there are still uncertainties about relationships between the groups involved.

 

Arachnids lack some features of other chelicerates, including backward-pointing mouths and gnathobases ("jaw bases") at the bases of their legs; both of these features are part of the ancestral arthropod feeding system. Instead, they have mouths that point forwards and downwards, and all have some means of breathing air. Spiders (Araneae) are distinguished from other arachnid groups by several characteristics, including spinnerets and, in males, pedipalps that are specially adapted for sperm transfer.

 

TAXONOMY

Spiders are divided into two suborders, Mesothelae and Opisthothelae, of which the latter contains two infraorders, Mygalomorphae and Araneomorphae. Nearly 46,000 living species of spiders (order Araneae) have been identified and are currently grouped into about 114 families and about 4,000 genera by arachnologists.

 

WIKIPEDIA

Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms. Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. As of November 2015, at least 45,700 spider species, and 114 families have been recorded by taxonomists. However, there has been dissension within the scientific community as to how all these families should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.

 

Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.

 

Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appeared in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets. True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving suborder, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before 200 million years ago.

 

A herbivorous species, Bagheera kiplingi, was described in 2008, but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, and they liquefy their food by flooding it with digestive enzymes and grinding it with the bases of their pedipalps, as they do not have true jaws.

 

Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity.

 

While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers. An abnormal fear of spiders is called arachnophobia.

 

DESCRIPTION

BODY PLAN

Spiders are chelicerates and therefore arthropods. As arthropods they have: segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo.[7] Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the cephalothorax or prosoma, is a complete fusion of the segments that in an insect would form two separate tagmata, the head and thorax; the rear tagma is called the abdomen or opisthosoma. In spiders, the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel. The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods. In fact, chelicerates' only appendages ahead of the mouth are a pair of chelicerae, and they lack anything that would function directly as "jaws". The first appendages behind the mouth are called pedipalps, and serve different functions within different groups of chelicerates.

 

Spiders and scorpions are members of one chelicerate group, the arachnids. Scorpions' chelicerae have three sections and are used in feeding. Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use. The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food. Scorpions' pedipalps generally form large claws for capturing prey, while those of spiders are fairly small appendages whose bases also act as an extension of the mouth; in addition, those of male spiders have enlarged last sections used for sperm transfer.

 

In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk. The upper surface of the cephalothorax is covered by a single, convex carapace, while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface.

 

Like other arthropods, spiders are coelomates in which the coelom is reduced to small areas round the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows. The heart is a tube in the upper part of the body, with a few ostia that act as non-return valves allowing blood to enter the heart from the hemocoel but prevent it from leaving before it reaches the front end. However, in spiders, it occupies only the upper part of the abdomen, and blood is discharged into the hemocoel by one artery that opens at the rear end of the abdomen and by branching arteries that pass through the pedicle and open into several parts of the cephalothorax. Hence spiders have open circulatory systems. The blood of many spiders that have book lungs contains the respiratory pigment hemocyanin to make oxygen transport more efficient.

 

Spiders have developed several different respiratory anatomies, based on book lungs, a tracheal system, or both. Mygalomorph and Mesothelae spiders have two pairs of book lungs filled with haemolymph, where openings on the ventral surface of the abdomen allow air to enter and diffuse oxygen. This is also the case for some basal araneomorph spiders, like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs. The trachea system has most likely evolved in small ancestors to help resist desiccation. The trachea were originally connected to the surroundings through a pair of openings called spiracles, but in the majority of spiders this pair of spiracles has fused into a single one in the middle, and moved backwards close to the spinnerets. Spiders that have tracheae generally have higher metabolic rates and better water conservation. Spiders are ectotherms, so environmental temperatures affect their activity.

 

FEEDING, DIGESTION AND EXCRETION

Uniquely among chelicerates, the final sections of spiders' chelicerae are fangs, and the great majority of spiders can use them to inject venom into prey from venom glands in the roots of the chelicerae. The family Uloboridae has lost its venom glands, and kills its prey with silk instead. Like most arachnids, including scorpions, spiders have a narrow gut that can only cope with liquid food and spiders have two sets of filters to keep solids out. They use one of two different systems of external digestion. Some pump digestive enzymes from the midgut into the prey and then suck the liquified tissues of the prey into the gut, eventually leaving behind the empty husk of the prey. Others grind the prey to pulp using the chelicerae and the bases of the pedipalps, while flooding it with enzymes; in these species, the chelicerae and the bases of the pedipalps form a preoral cavity that holds the food they are processing.

 

The stomach in the cephalothorax acts as a pump that sends the food deeper into the digestive system. The mid gut bears many digestive ceca, compartments with no other exit, that extract nutrients from the food; most are in the abdomen, which is dominated by the digestive system, but a few are found in the cephalothorax.

 

Most spiders convert nitrogenous waste products into uric acid, which can be excreted as a dry material. Malphigian tubules ("little tubes") extract these wastes from the blood in the hemocoel and dump them into the cloacal chamber, from which they are expelled through the anus. Production of uric acid and its removal via Malphigian tubules are a water-conserving feature that has evolved independently in several arthropod lineages that can live far away from water,[14] for example the tubules of insects and arachnids develop from completely different parts of the embryo. However, a few primitive spiders, the sub-order Mesothelae and infra-order Mygalomorphae, retain the ancestral arthropod nephridia ("little kidneys"), which use large amounts of water to excrete nitrogenous waste products as ammonia.

 

CENTRAL NERVOS SYSTEM

The basic arthropod central nervous system consists of a pair of nerve cords running below the gut, with paired ganglia as local control centers in all segments; a brain formed by fusion of the ganglia for the head segments ahead of and behind the mouth, so that the esophagus is encircled by this conglomeration of ganglia. Except for the primitive Mesothelae, of which the Liphistiidae are the sole surviving family, spiders have the much more centralized nervous system that is typical of arachnids: all the ganglia of all segments behind the esophagus are fused, so that the cephalothorax is largely filled with nervous tissue and there are no ganglia in the abdomen; in the Mesothelae, the ganglia of the abdomen and the rear part of the cephalothorax remain unfused.

 

Despite the relatively small central nervous system, some spiders (like Portia) exhibit complex behaviour, including the ability to use a trial-and-error approach.

 

SENSE ORGANS

EYES

Most spiders have four pairs of eyes on the top-front area of the cephalothorax, arranged in patterns that vary from one family to another. The pair at the front are of the type called pigment-cup ocelli ("little eyes"), which in most arthropods are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup. However, the main eyes at the front of spiders' heads are pigment-cup ocelli that are capable of forming images. The other eyes are thought to be derived from the compound eyes of the ancestral chelicerates, but no longer have the separate facets typical of compound eyes. Unlike the main eyes, in many spiders these secondary eyes detect light reflected from a reflective tapetum lucidum, and wolf spiders can be spotted by torch light reflected from the tapeta. On the other hand, jumping spiders' secondary eyes have no tapeta. Some jumping spiders' visual acuity exceeds by a factor of ten that of dragonflies, which have by far the best vision among insects; in fact the human eye is only about five times sharper than a jumping spider's. They achieve this by a telephoto-like series of lenses, a four-layer retina and the ability to swivel their eyes and integrate images from different stages in the scan. The downside is that the scanning and integrating processes are relatively slow.

 

There are spiders with a reduced number of eyes, of these those with six-eyes are the most numerous and are missing a pair of eyes on the anterior median line, others species have four-eyes and some just two. Cave dwelling species have no eyes, or possess vestigial eyes incapable of sight.

 

OTHER SENSES

As with other arthropods, spiders' cuticles would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly bristles called setae, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell, often by means of setae. Pedipalps carry a large number of such setae sensitive to contact chemicals and air-borne smells, such as female pheromones. Spiders also have in the joints of their limbs slit sensillae that detect forces and vibrations. In web-building spiders, all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively.

 

Like most arthropods, spiders lack balance and acceleration sensors and rely on their eyes to tell them which way is up. Arthropods' proprioceptors, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well understood. On the other hand, little is known about what other internal sensors spiders or other arthropods may have.

 

LOCOMOTION

Each of the eight legs of a spider consists of seven distinct parts. The part closest to and attaching the leg to the cephalothorax is the coxa; the next segment is the short trochanter that works as a hinge for the following long segment, the femur; next is the spider's knee, the patella, which acts as the hinge for the tibia; the metatarsus is next, and it connects the tibia to the tarsus (which may be thought of as a foot of sorts); the tarsus ends in a claw made up of either two or three points, depending on the family to which the spider belongs. Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, spiders and a few other groups still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors. The only extensor muscles in spider legs are located in the three hip joints (bordering the coxa and the trochanter). As a result, a spider with a punctured cephalothorax cannot extend its legs, and the legs of dead spiders curl up. Spiders can generate pressures up to eight times their resting level to extend their legs, and jumping spiders can jump up to 50 times their own length by suddenly increasing the blood pressure in the third or fourth pair of legs. Although larger spiders use hydraulics to straighten their legs, unlike smaller jumping spiders they depend on their flexor muscles to generate the propulsive force for their jumps.

 

Most spiders that hunt actively, rather than relying on webs, have dense tufts of fine hairs between the paired claws at the tips of their legs. These tufts, known as scopulae, consist of bristles whose ends are split into as many as 1,000 branches, and enable spiders with scopulae to walk up vertical glass and upside down on ceilings. It appears that scopulae get their grip from contact with extremely thin layers of water on surfaces. Spiders, like most other arachnids, keep at least four legs on the surface while walking or running.

 

SILK PRODUCTION

The abdomen has no appendages except those that have been modified to form one to four (usually three) pairs of short, movable spinnerets, which emit silk. Each spinneret has many spigots, each of which is connected to one silk gland. There are at least six types of silk gland, each producing a different type of silk.

 

Silk is mainly composed of a protein very similar to that used in insect silk. It is initially a liquid, and hardens not by exposure to air but as a result of being drawn out, which changes the internal structure of the protein. It is similar in tensile strength to nylon and biological materials such as chitin, collagen and cellulose, but is much more elastic. In other words, it can stretch much further before breaking or losing shape.

 

Some spiders have a cribellum, a modified spinneret with up to 40,000 spigots, each of which produces a single very fine fiber. The fibers are pulled out by the calamistrum, a comb-like set of bristles on the jointed tip of the cribellum, and combined into a composite woolly thread that is very effective in snagging the bristles of insects. The earliest spiders had cribella, which produced the first silk capable of capturing insects, before spiders developed silk coated with sticky droplets. However, most modern groups of spiders have lost the cribellum.

 

Tarantulas also have silk glands in their feet.

 

Even species that do not build webs to catch prey use silk in several ways: as wrappers for sperm and for fertilized eggs; as a "safety rope"; for nest-building; and as "parachutes" by the young of some species.

 

REPRODUCTION AND LIFE CYCLE

Spiders reproduce sexually and fertilization is internal but indirect, in other words the sperm is not inserted into the female's body by the male's genitals but by an intermediate stage. Unlike many land-living arthropods, male spiders do not produce ready-made spermatophores (packages of sperm), but spin small sperm webs on to which they ejaculate and then transfer the sperm to special syringe-like structures, palpal bulbs or palpal organs, borne on the tips of the pedipalps of mature males. When a male detects signs of a female nearby he checks whether she is of the same species and whether she is ready to mate; for example in species that produce webs or "safety ropes", the male can identify the species and sex of these objects by "smell".

 

Spiders generally use elaborate courtship rituals to prevent the large females from eating the small males before fertilization, except where the male is so much smaller that he is not worth eating. In web-weaving species, precise patterns of vibrations in the web are a major part of the rituals, while patterns of touches on the female's body are important in many spiders that hunt actively, and may "hypnotize" the female. Gestures and dances by the male are important for jumping spiders, which have excellent eyesight. If courtship is successful, the male injects his sperm from the palpal bulbs into the female's genital opening, known as the epigyne, on the underside of her abdomen. Female's reproductive tracts vary from simple tubes to systems that include seminal receptacles in which females store sperm and release it when they are ready.

 

Males of the genus Tidarren amputate one of their palps before maturation and enter adult life with one palp only. The palps are 20% of male's body mass in this species, and detaching one of the two improves mobility. In the Yemeni species Tidarren argo, the remaining palp is then torn off by the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime, the female feeds on the palpless male. In over 60% of cases, the female of the Australian redback spider kills and eats the male after it inserts its second palp into the female's genital opening; in fact, the males co-operate by trying to impale themselves on the females' fangs. Observation shows that most male redbacks never get an opportunity to mate, and the "lucky" ones increase the likely number of offspring by ensuring that the females are well-fed. However, males of most species survive a few matings, limited mainly by their short life spans. Some even live for a while in their mates' webs.

 

Females lay up to 3,000 eggs in one or more silk egg sacs, which maintain a fairly constant humidity level. In some species, the females die afterwards, but females of other species protect the sacs by attaching them to their webs, hiding them in nests, carrying them in the chelicerae or attaching them to the spinnerets and dragging them along.

 

Baby spiders pass all their larval stages inside the egg and hatch as spiderlings, very small and sexually immature but similar in shape to adults. Some spiders care for their young, for example a wolf spider's brood cling to rough bristles on the mother's back, and females of some species respond to the "begging" behaviour of their young by giving them their prey, provided it is no longer struggling, or even regurgitate food.

 

Like other arthropods, spiders have to molt to grow as their cuticle ("skin") cannot stretch. In some species males mate with newly molted females, which are too weak to be dangerous to the males. Most spiders live for only one to two years, although some tarantulas can live in captivity for over 20 years.

 

SIZE

Spiders occur in a large range of sizes. The smallest, Patu digua from Colombia, are less than 0.37 mm in body length. The largest and heaviest spiders occur among tarantulas, which can have body lengths up to 90 mm and leg spans up to 250 mm.

 

ECOLOGY AND BEHAVIOR

NON-PREDATORY FEEDING

Although spiders are generally regarded as predatory, the jumping spider Bagheera kiplingi gets over 90% of its food from fairly solid plant material produced by acacias as part of a mutually beneficial relationship with a species of ant.

 

Juveniles of some spiders in the families Anyphaenidae, Corinnidae, Clubionidae, Thomisidae and Salticidae feed on plant nectar. Laboratory studies show that they do so deliberately and over extended periods, and periodically clean themselves while feeding. These spiders also prefer sugar solutions to plain water, which indicates that they are seeking nutrients. Since many spiders are nocturnal, the extent of nectar consumption by spiders may have been underestimated. Nectar contains amino acids, lipids, vitamins and minerals in addition to sugars, and studies have shown that other spider species live longer when nectar is available. Feeding on nectar avoids the risks of struggles with prey, and the costs of producing venom and digestive enzymes.

 

Various species are known to feed on dead arthropods (scavenging), web silk, and their own shed exoskeletons. Pollen caught in webs may also be eaten, and studies have shown that young spiders have a better chance of survival if they have the opportunity to eat pollen. In captivity, several spider species are also known to feed on bananas, marmalade, milk, egg yolk and sausages.

 

METHODS OF CAPTURING PREY

The best-known method of prey capture is by means of sticky webs. Varying placement of webs allows different species of spider to trap different insects in the same area, for example flat horizontal webs trap insects that fly up from vegetation underneath while flat vertical webs trap insects in horizontal flight. Web-building spiders have poor vision, but are extremely sensitive to vibrations.

 

Females of the water spider Argyroneta aquatica build underwater "diving bell" webs that they fill with air and use for digesting prey, molting, mating and raising offspring. They live almost entirely within the bells, darting out to catch prey animals that touch the bell or the threads that anchor it. A few spiders use the surfaces of lakes and ponds as "webs", detecting trapped insects by the vibrations that these cause while struggling.

 

Net-casting spiders weave only small webs, but then manipulate them to trap prey. Those of the genus Hyptiotes and the family Theridiosomatidae stretch their webs and then release them when prey strike them, but do not actively move their webs. Those of the family Deinopidae weave even smaller webs, hold them outstretched between their first two pairs of legs, and lunge and push the webs as much as twice their own body length to trap prey, and this move may increase the webs' area by a factor of up to ten. Experiments have shown that Deinopis spinosus has two different techniques for trapping prey: backwards strikes to catch flying insects, whose vibrations it detects; and forward strikes to catch ground-walking prey that it sees. These two techniques have also been observed in other deinopids. Walking insects form most of the prey of most deinopids, but one population of Deinopis subrufa appears to live mainly on tipulid flies that they catch with the backwards strike.

 

Mature female bolas spiders of the genus Mastophora build "webs" that consist of only a single "trapeze line", which they patrol. They also construct a bolas made of a single thread, tipped with a large ball of very wet sticky silk. They emit chemicals that resemble the pheromones of moths, and then swing the bolas at the moths. Although they miss on about 50% of strikes, they catch about the same weight of insects per night as web-weaving spiders of similar size. The spiders eat the bolas if they have not made a kill in about 30 minutes, rest for a while, and then make new bolas. Juveniles and adult males are much smaller and do not make bolas. Instead they release different pheromones that attract moth flies, and catch them with their front pairs of legs.

 

The primitive Liphistiidae, the "trapdoor spiders" of the family Ctenizidae and many tarantulas are ambush predators that lurk in burrows, often closed by trapdoors and often surrounded by networks of silk threads that alert these spiders to the presence of prey. Other ambush predators do without such aids, including many crab spiders, and a few species that prey on bees, which see ultraviolet, can adjust their ultraviolet reflectance to match the flowers in which they are lurking. Wolf spiders, jumping spiders, fishing spiders and some crab spiders capture prey by chasing it, and rely mainly on vision to locate prey.Some jumping spiders of the genus Portia hunt other spiders in ways that seem intelligent, outflanking their victims or luring them from their webs. Laboratory studies show that Portia's instinctive tactics are only starting points for a trial-and-error approach from which these spiders learn very quickly how to overcome new prey species. However, they seem to be relatively slow "thinkers", which is not surprising, as their brains are vastly smaller than those of mammalian predators.

 

Ant-mimicking spiders face several challenges: they generally develop slimmer abdomens and false "waists" in the cephalothorax to mimic the three distinct regions (tagmata) of an ant's body; they wave the first pair of legs in front of their heads to mimic antennae, which spiders lack, and to conceal the fact that they have eight legs rather than six; they develop large color patches round one pair of eyes to disguise the fact that they generally have eight simple eyes, while ants have two compound eyes; they cover their bodies with reflective hairs to resemble the shiny bodies of ants. In some spider species, males and females mimic different ant species, as female spiders are usually much larger than males. Ant-mimicking spiders also modify their behavior to resemble that of the target species of ant; for example, many adopt a zig-zag pattern of movement, ant-mimicking jumping spiders avoid jumping, and spiders of the genus Synemosyna walk on the outer edges of leaves in the same way as Pseudomyrmex. Ant-mimicry in many spiders and other arthropods may be for protection from predators that hunt by sight, including birds, lizards and spiders. However, several ant-mimicking spiders prey either on ants or on the ants' "livestock", such as aphids. When at rest, the ant-mimicking crab spider Amyciaea does not closely resemble Oecophylla, but while hunting it imitates the behavior of a dying ant to attract worker ants. After a kill, some ant-mimicking spiders hold their victims between themselves and large groups of ants to avoid being attacked.

 

DEFENSE

There is strong evidence that spiders' coloration is camouflage that helps them to evade their major predators, birds and parasitic wasps, both of which have good color vision. Many spider species are colored so as to merge with their most common backgrounds, and some have disruptive coloration, stripes and blotches that break up their outlines. In a few species, such as the Hawaiian happy-face spider, Theridion grallator, several coloration schemes are present in a ratio that appears to remain constant, and this may make it more difficult for predators to recognize the species. Most spiders are insufficiently dangerous or unpleasant-tasting for warning coloration to offer much benefit. However, a few species with powerful venoms, large jaws or irritant hairs have patches of warning colors, and some actively display these colors when threatened.

 

Many of the family Theraphosidae, which includes tarantulas and baboon spiders, have urticating hairs on their abdomens and use their legs to flick them at attackers. These hairs are fine setae (bristles) with fragile bases and a row of barbs on the tip. The barbs cause intense irritation but there is no evidence that they carry any kind of venom. A few defend themselves against wasps by including networks of very robust threads in their webs, giving the spider time to flee while the wasps are struggling with the obstacles. The golden wheeling spider, Carparachne aureoflava, of the Namibian desert escapes parasitic wasps by flipping onto its side and cartwheeling down sand dunes.

 

SOZIAL SPIDERS

A few spider species that build webs live together in large colonies and show social behavior, although not as complex as in social insects. Anelosimus eximius (in the family Theridiidae) can form colonies of up to 50,000 individuals. The genus Anelosimus has a strong tendency towards sociality: all known American species are social, and species in Madagascar are at least somewhat social. Members of other species in the same family but several different genera have independently developed social behavior. For example, although Theridion nigroannulatum belongs to a genus with no other social species, T. nigroannulatum build colonies that may contain several thousand individuals that co-operate in prey capture and share food. Other communal spiders include several Philoponella species (family Uloboridae), Agelena consociata (family Agelenidae) and Mallos gregalis (family Dictynidae). Social predatory spiders need to defend their prey against kleptoparasites ("thieves"), and larger colonies are more successful in this. The herbivorous spider Bagheera kiplingi lives in small colonies which help to protect eggs and spiderlings. Even widow spiders (genus Latrodectus), which are notoriously cannibalistic, have formed small colonies in captivity, sharing webs and feeding together.

 

WEB TYPES

There is no consistent relationship between the classification of spiders and the types of web they build: species in the same genus may build very similar or significantly different webs. Nor is there much correspondence between spiders' classification and the chemical composition of their silks. Convergent evolution in web construction, in other words use of similar techniques by remotely related species, is rampant. Orb web designs and the spinning behaviors that produce them are the best understood. The basic radial-then-spiral sequence visible in orb webs and the sense of direction required to build them may have been inherited from the common ancestors of most spider groups. However, the majority of spiders build non-orb webs. It used to be thought that the sticky orb web was an evolutionary innovation resulting in the diversification of the Orbiculariae. Now, however, it appears that non-orb spiders are a sub-group that evolved from orb-web spiders, and non-orb spiders have over 40% more species and are four times as abundant as orb-web spiders. Their greater success may be because sphecid wasps, which are often the dominant predators of spiders, much prefer to attack spiders that have flat webs.

 

ORB WEBS

About half the potential prey that hit orb webs escape. A web has to perform three functions: intercepting the prey (intersection), absorbing its momentum without breaking (stopping), and trapping the prey by entangling it or sticking to it (retention). No single design is best for all prey. For example: wider spacing of lines will increase the web's area and hence its ability to intercept prey, but reduce its stopping power and retention; closer spacing, larger sticky droplets and thicker lines would improve retention, but would make it easier for potential prey to see and avoid the web, at least during the day. However, there are no consistent differences between orb webs built for use during the day and those built for use at night. In fact, there is no simple relationship between orb web design features and the prey they capture, as each orb-weaving species takes a wide range of prey.

 

The hubs of orb webs, where the spiders lurk, are usually above the center, as the spiders can move downwards faster than upwards. If there is an obvious direction in which the spider can retreat to avoid its own predators, the hub is usually offset towards that direction.

 

Horizontal orb webs are fairly common, despite being less effective at intercepting and retaining prey and more vulnerable to damage by rain and falling debris. Various researchers have suggested that horizontal webs offer compensating advantages, such as reduced vulnerability to wind damage; reduced visibility to prey flying upwards, because of the back-lighting from the sky; enabling oscillations to catch insects in slow horizontal flight. However, there is no single explanation for the common use of horizontal orb webs.

 

Spiders often attach highly visible silk bands, called decorations or stabilimenta, to their webs. Field research suggests that webs with more decorative bands captured more prey per hour. However, a laboratory study showed that spiders reduce the building of these decorations if they sense the presence of predators.

 

In 1973, Skylab 3 took two orb-web spiders into space to test their web-spinning capabilities in zero gravity. At first, both produced rather sloppy webs, but they adapted quickly.

Tangleweb spiders (cobweb spiders)

 

Members of the family Theridiidae weave irregular, tangled, three-dimensional webs, popularly known as cobwebs. There seems to be an evolutionary trend towards a reduction in the amount of sticky silk used, leading to its total absence in some species. The construction of cobwebs is less stereotyped than that of orb-webs, and may take several days.

 

OTHER TYPES OF WEBS

The Linyphiidae generally make horizontal but uneven sheets, with tangles of stopping threads above. Insects that hit the stopping threads fall onto the sheet or are shaken onto it by the spider, and are held by sticky threads on the sheet until the spider can attack from below.

 

EVOLUTION

FOSSIL RECORD

Although the fossil record of spiders is considered poor, almost 1000 species have been described from fossils. Because spiders' bodies are quite soft, the vast majority of fossil spiders have been found preserved in amber. The oldest known amber that contains fossil arthropods dates from 130 million years ago in the Early Cretaceous period. In addition to preserving spiders' anatomy in very fine detail, pieces of amber show spiders mating, killing prey, producing silk and possibly caring for their young. In a few cases, amber has preserved spiders' egg sacs and webs, occasionally with prey attached; the oldest fossil web found so far is 100 million years old. Earlier spider fossils come from a few lagerstätten, places where conditions were exceptionally suited to preserving fairly soft tissues.

 

The oldest known exclusively terrestrial arachnid is the trigonotarbid Palaeotarbus jerami, from about 420 million years ago in the Silurian period, and had a triangular cephalothorax and segmented abdomen, as well as eight legs and a pair of pedipalps. Attercopus fimbriunguis, from 386 million years ago in the Devonian period, bears the earliest known silk-producing spigots, and was therefore hailed as a spider at the time of its discovery. However, these spigots may have been mounted on the underside of the abdomen rather than on spinnerets, which are modified appendages and whose mobility is important in the building of webs. Hence Attercopus and the similar Permian arachnid Permarachne may not have been true spiders, and probably used silk for lining nests or producing egg-cases rather than for building webs. The largest known fossil spider as of 2011 is the araneid Nephila jurassica, from about 165 million years ago, recorded from Daohuogo, Inner Mongolia in China. Its body length is almost 25 mm.

 

Several Carboniferous spiders were members of the Mesothelae, a primitive group now represented only by the Liphistiidae. The mesothelid Paleothele montceauensis, from the Late Carboniferous over 299 million years ago, had five spinnerets. Although the Permian period 299 to 251 million years ago saw rapid diversification of flying insects, there are very few fossil spiders from this period.

 

The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the Triassic well before 200 million years ago. Some Triassic mygalomorphs appear to be members of the family Hexathelidae, whose modern members include the notorious Sydney funnel-web spider, and their spinnerets appear adapted for building funnel-shaped webs to catch jumping insects. Araneomorphae account for the great majority of modern spiders, including those that weave the familiar orb-shaped webs. The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families.

 

FAMILY TREE

It is now agreed that spiders (Araneae) are monophyletic (i.e., members of a group of organisms that form a clade, consisting of a last common ancestor and all of its descendants). There has been debate about what their closest evolutionary relatives are, and how all of these evolved from the ancestral chelicerates, which were marine animals. The cladogram on the right is based on J. W. Shultz' analysis (2007). Other views include proposals that: scorpions are more closely related to the extinct marine scorpion-like eurypterids than to spiders; spiders and Amblypygi are a monophyletic group. The appearance of several multi-way branchings in the tree on the right shows that there are still uncertainties about relationships between the groups involved.

 

Arachnids lack some features of other chelicerates, including backward-pointing mouths and gnathobases ("jaw bases") at the bases of their legs; both of these features are part of the ancestral arthropod feeding system. Instead, they have mouths that point forwards and downwards, and all have some means of breathing air. Spiders (Araneae) are distinguished from other arachnid groups by several characteristics, including spinnerets and, in males, pedipalps that are specially adapted for sperm transfer.

 

TAXONOMY

Spiders are divided into two suborders, Mesothelae and Opisthothelae, of which the latter contains two infraorders, Mygalomorphae and Araneomorphae. Nearly 46,000 living species of spiders (order Araneae) have been identified and are currently grouped into about 114 families and about 4,000 genera by arachnologists.

 

WIKIPEDIA

Abstract

To understand the evolutionary significance of geographic variation, one must identify the factors that generate phenotypic differences among populations. I examined the causes of geographic variation in and evolutionary history of number of trunk vertebrae in slender salamanders. Batrachoseps (Caudata: Plethodontidae). Number of trunk vertebrae varies at many taxonomic levels within Batrachoseps. Parallel clines in number occur along an environmental gradient in three lineages in the Coast Ranges of California. These parallel clines may signal either adaptation or a shared phenotypically plastic response to the environmental gradient. By raising eggs from 10 populations representing four species of Batrachoseps, I demonstrated that number of trunk vertebrae can be altered by the developmental temperature; however, the degree of plasticity is insufficient to account for geographic variation. Thus, the geographic variation results largely from genetic variation. Number of trunk vertebrae covaries with body size and shape in diverse vertebrate taxa, including Batrachoseps. I hypothesize that selection for different degrees of elongation, possibly related to fossoriality, has led to the extensive evolution of number of trunk vertebrae in Batrachoseps. Analysis of intrapopulational variation revealed sexual dimorphism in both body shape and number of trunk vertebrae, but no correlation between these variables in either sex. Females are more elongate than males, a pattern that has been attributed to fecundity selection in other taxa. Patterns of covariation among different classes of vertebrae suggest that some intrapopulational variation in number results from changes in vertebral identity rather than changes in segmentation.

Elizabeth L. Jockusch

Evolution

 

MORE INFORMATION

 

Images in this gallery were captured by:

 

Mark Smith M.S. Geoscientist mark@macroscopicsolutions.com

 

Daniel Saftner B.S. Geoscientist and Returned Peace Corps Volunteer daniel@macroscopicsolutions.com

 

Annette Evans Ph.D. Student at the University of Connecticut annette@macroscopicsolutions.com

Harris's hawk (Parabuteo unicinctus), formerly known as the bay-winged hawk, dusky hawk, and sometimes a wolf hawk, and known in Latin America as peuco, is a medium-large bird of prey that breeds from the southwestern United States south to Chile, central Argentina, and Brazil. This bird is sometimes reported to be at large in Western Europe, especially Britain, but it is a popular species in falconry and these records almost invariably all refer to escapes from captivity.

 

The name is derived from the Greek para, meaning beside, near or like, and the Latin buteo, referring to a kind of buzzard; uni meaning once; and cinctus meaning girdled, referring to the white band at the tip of the tail. John James Audubon gave this bird its English name in honor of his ornithological companion, financial supporter, and friend Edward Harris.

 

Harris's hawk is notable for its behavior of hunting cooperatively in packs consisting of tolerant groups, while other raptors often hunt alone. Harris hawks' social nature has been attributed to their intelligence, which makes them easy to train and has made them a popular bird for use in falconry.

 

Description

This medium-large hawk is roughly intermediate in size between a peregrine falcon (Falco peregrinus) and a red-tailed hawk (Buteo jamaicensis). Harris's hawks range in length from 46 to 59 cm (18 to 23 in) and generally have a wingspan of about 103 to 120 cm (41 to 47 in). These hawks have a brownish plumage, reddish shoulders, and tail feathers with a white base and white tip.

 

They exhibit sexual dimorphism with the females being larger by about 35%. In the United States, the average weight for adult males is about 701 g (1.545 lb), with a range of 546 to 850 g (1.204 to 1.874 lb), while the adult female average is 1,029 g (2.269 lb), with a range of 766 to 1,633 g (1.689 to 3.600 lb). They have dark brown plumage with chestnut shoulders, wing linings, and thighs, white on the base and tip of the tail, long, yellow legs, and a yellow cere. The vocalizations of Harris's hawk are very harsh sounds.

 

The lifespan of Harris's Hawk is 10–12 years in the wild and 20–25 years in captivity.

 

Juvenile

The juvenile Harris's hawk is mostly streaked with buff and appears much lighter than the dark adults. When in flight, the undersides of the juveniles' wings are buff-colored with brown streaking. They can look unlike adults at first glance, but the identical chestnut plumage is an aid for identification.

 

Subspecies

P. u. superior: found in Baja California, Arizona, Sonora, and Sinaloa. P. u. superior was believed to have longer tails and wings and to be more blackish than P. u. harrisi. However, the sample size of the original study was quite small, with only five males and six females. Later research has concluded that there is not as strong a physical difference as was originally assumed. Other ecological differences, such as latitudinal cline were also brought up as arguments against the validity of the subspecies segmentation.

P. u. harrisi: found in Texas, eastern Mexico, and much of Central America.

P. u. unicinctus: found exclusively in South America. It is smaller than the North American subspecies and the adult's dark brown ventrum is streaked or flecked with white or whitish.

Taxonomy

Robert Ridgway placed Harris' Hawk in its own new subgenus Urubitinga (Antenor) in 1873, and introduced the generic name Parabuteo in 1874. Richard Bowdler Sharpe also separated Harris' Hawk to a monotypic genus, Erythrocnema, in 1874. In his Catalogue of Birds in the British Museum, Sharpe gives an extensive synonymy, with various authors having earlier placed harrisii in three genera and unicinctus in eleven.

 

Distribution and habitat

Harris's hawks live in sparse woodland and semi-desert, as well as marshes (with some trees) in some parts of their range (Howell and Webb 1995), including mangrove swamps, as in parts of their South American range. Harris's hawks are permanent residents and do not migrate. Important perches and nest supports are provided by scattered larger trees or other features (e.g., power poles, woodland edges, standing dead trees, live trees, boulders, and saguaros).

 

The wild Harris's hawk population is declining due to habitat loss; however, under some circumstances, they have been known to move into developed areas.

 

Behaviour

This species occurs in relatively stable groups. A dominance hierarchy occurs in Harris's hawks, wherein the mature female is the dominant bird, followed by the adult male and then the young of previous years. Groups typically include from two to seven birds. Not only do birds cooperate in hunting, but they also assist in the nesting process. No other bird of prey is known to hunt in groups as routinely as this species.

 

Breeding

They nest in small trees, shrubby growth, or cacti. The nests are often compact, made of sticks, plant roots, and stems and are often lined with leaves, moss, bark, and plant roots. They are built mainly by the female. There are usually two to four white to blueish-white eggs sometimes with a speckling of pale brown or gray. The nestlings start light buff, but in five to six days turn a rich brown.

 

Very often, there will be three hawks attending one nest: two males and one female. Whether or not this is polyandry is debated, as it may be confused with backstanding (one bird standing on another's back). The female does most of the incubation. The eggs hatch in 31 to 36 days. The young begin to explore outside the nest at 38 days, and fledge, or start to fly, at 45 to 50 days. The female sometimes breeds two or three times in a year. Young may stay with their parents for up to three years, helping to raise later broods. Nests are known to be predated by coyotes (Canis latrans), golden eagles (Aquila chrysaetos), red-tailed hawks (Buteo jamaicensis), great horned owls (Bubo virginianus), and flocks of common ravens (Corvus corax), predators possibly too formidable to be fully displaced by Harris's hawk's cooperative nest defenses. No accounts show predation on adults in the United States and Harris's hawk may be considered an apex predator, although presumably predators like eagles and great horned owls would be capable of killing them. In Chile, black-chested buzzard-eagles (Geranoaetus melanoleucus) are likely predators.

 

Feeding

The majority of Harris hawk's prey are mammals, including ground squirrels, rabbits, and larger black-tailed jackrabbits (Lepus californicus). Birds from the size of small passerines such as diuca finch (Diuca diuca) to adult great egret (Ardea alba) and half-grown wild turkey (Meleagris gallapavo) can be taken. In one instance, the lone Harris hawk successfully killed a subadult great blue heron (Ardea herodias). Reptiles such as lizards and snakes are additionally taken as well as large insects.

 

When hunting in groups, Harris's hawk can take large prey effectively, such as desert cottontail (Syvilagus auduboni), the leading prey species in the north of Harris's hawk's range, usually weighs 800 g (1.8 lb) or less. Even adult black-tailed jackrabbits weighing more than 2,000 g (4.4 lb) can be successfully taken by a pack of harris hawks.

 

Undoubtedly because it pursues large prey often, this hawk has larger and stronger feet, with long talons, and a larger, more prominent hooked beak than most other raptors around its size. Locally, other buteonine hawks, including the ferruginous hawk, the red-tailed hawk, and the white-tailed hawk also hunt primarily cottontails and jackrabbits, but each is bigger, weighing about 500 g (18 oz), 300 g (11 oz) and 200 g (7.1 oz), respectively, more on average than a Harris's hawk.

 

In the Southwestern United States, the most common prey species (in descending order of prevalence) are desert cottontail (Syvilagus auduboni), eastern cottontail (Syvilagus floridanus), black-tailed jackrabbit (Lepus californicus), ground squirrels (Ammopsermophilus spp. and Spermophilus spp.), woodrats (Neotoma spp.), kangaroo rats (Dipodomys spp.), pocket gophers (Geomys and Thomomys spp.), Gambel's quail (Callipepla gambelii), scaled quail (C. squamata), northern bobwhite (Colinus virginianus), cactus wren (Campylorhynchus brunneicapillus), northern mockingbird (Mimus polyglottos), desert spiny lizards (Sceloporus magister), and skinks (Eumeces spp.) In the tropics, Harris's hawks have adapted to taking prey of several varieties, including those like chickens and European rabbits introduced by man. In Chile, the common degu (Octodon degus) makes up 67.5% of the prey.

 

Hunting

While most raptors are solitary, only coming together for breeding and migration, Harris's hawks will hunt in cooperative groups of two to six. This is believed to be an adaptation to the lack of prey in the desert climate in which they live. In one hunting technique, a small group flies ahead and scouts, then another group member flies ahead and scouts, and this continues until prey is bagged and shared. In another, all the hawks spread around the prey and one bird flushes it out. Harris's hawks will often chase prey on foot, and are quite fast on the ground and their long, yellow legs are adapted for this, as most hawks do not spend as much time on the ground. Groups of Harris's hawks tend to be more successful at capturing prey than lone hawks, with groups of two to four individuals having ~10% higher success rates per extra individual.

 

Relationship with humans

Falconry

Since about 1980, Harris's hawks have been increasingly used in falconry and are now the most popular hawks in the West (outside of Asia) for that purpose, as they are one of the easiest to train and the most social.

 

Trained Harris's hawks have been used to remove an unwanted pigeon population from London's Trafalgar Square, and from the tennis courts at Wimbledon.

 

Trained Harris's hawks have been used for bird abatement by falconry experts in Canada and the United States at various locations including airports, resorts, landfill sites, and industrial sites.

 

In art

John James Audubon illustrated Harris's hawk in The Birds of America (published in London, 1827–38) as Plate 392 with the title "Louisiana Hawk -Buteo harrisi". The image was engraved and colored by the Robert Havell, London workshops in 1837. The original watercolor by Audubon was purchased by the New York History Society where it remains to this day (January 2009).

Spotted this brothers sitting at the pavement. The torn clothes they are wearing, scar on the knees, soiled slippers, and the barefoot baby brother, really thought provoking on the condition they are living in.

 

This village they are staying in is located behind a dumping ground. moving uphill, populated by shelters built with wooden foundation and some concrete foundation. Within the village itself shows class segmentation of people.

The Brachycera are a suborder of the order Diptera. It is a major suborder consisting of around 120 families. Their most distinguishing characteristic is reduced antenna segmentation

1976 Bristol VRT/ECW C5038 in the Bristol Omnibus fleet was rebuilt to open top in February 1985 and renumbered 8618 and named "Dolphin". On 28 September 1985 it is seen in Weston-Super-Mare with Weston Badgerline fleetnames as part of the segmentation of Bristol Omnibus areas.

In approximately 7 months time (on October 7th, 2016 to be exact), the last Australian-designed & manufactured Ford Falcon will exit the production line at Broadmeadows in Melbourne. This will marktthe end of 57 years of Falcon production, and 92 years of Ford production in Australia.

 

The Falcon, rather than the Territory (which is also assembled in Broadmeadows) has been chosen due to the many years that this nameplate has been at the forefront of the Australian automotive market.

 

Unfortunately, increased competition, globalisation and market segmentation have all played their part in reducing the viability of producing cars in Australia. After Ford's exit in October 2016, the two other automotive producers in Australia, Holden (part of General Motors) and Toyota Australia are expected to close within 12 months or so.

 

The remaining bright spot is that Ford's Product Development activities in Australia have never been stronger.

 

The office campus in Broadmeadows has been turned over solely to Product Development and Design, becoming the Asia-Pacific Product Development Campus (APPDC) - a bit of a mouthful, such that employees still just call it 'Head Office'.

 

This facility is supported by full-vehicle testing at the You-Yangs Proving Ground outside Lara, and the Ford Reasearch & Development Centre in Geelong (at one end of the existing vehicle production site).

 

The model shown the FGX G6-E displays the current Ford 'look' draped over the FG platform, first launched in 2008. the model has a 4.0 litre, inline six-cylinder engine producing 195 kW in standard form, and up to 325 kW in its final turbocharged edition (The XR6 Sprint). An intermediate 270 kW tune is used for the G6-E Turbo, - a luxury-sport model.

Today only this gate remains to remember the palace of Tamerlane.

"The overall scale of the palace was impressive: the main courtyard alone, which has been reconstituted from the microrelief, was 120 - 125 m wide and 240 - 250 m long. The size of the other courtyards and of the outer perimeter of the palace has not been reconstructed owing to severe disturbance of the microrelief in the 15th - 16th centuries. Calculation of the proportions of the surviving elements of the site makes it fairly certain that the height of the main portal reached 70 m. It was topped by arched pinnacles (ko'ngra), while corner towers on a multifaceted pedestal were at least 80 m high. The main entrance portal was 50 m wide, and the arch had the largest span, 22.5 m, in Central Asia.

 

The architectural decor, featuring a wide variety of designs and colours, is particularly noteworthy in the artistic appearance of Ak-Saray. When using various techniques, however, the craftsmen bore in mind that the palace's main portal faced north, towards the capital, Samarkand. Given the poor light, the architects used only flat segmentation here and hence a continuous decorative treatment. The use of brick mosaic work, mainly dark and light blue in colour, forming large geometrical and epigraphic designs on a background of polished building brick, gives the portal a special softness of colour and an air of grand mystery."

(from "The architectural masterpieces of the emerald city" by Zafar Khakimov)

Urban Scenes and Scapes

 

"Usual Blurb" © by Wil Wardle. Please do not use this or any of my images without my permission.

 

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+++ DISCLAIMER +++Nothing you see here is real, even though the conversion or the presented background story might be based on historical facts. BEWARE!

  

Some background:

The Nakajima J9N Kitsuka (中島 橘花, "Orange Blossom", pronounced Kikka in Kanji used traditionally by the Japanese) was Japan's first jet aircraft. In internal IJN documents it was also called Kōkoku Nigō Heiki (皇国二号兵器, "Imperial Weapon No.2"). After the Japanese military attaché in Germany witnessed trials of the Messerschmitt Me 262 in 1942, the Imperial Japanese Navy issued a request to Nakajima to develop a similar aircraft to be used as a fast attack bomber. Among the specifications for the design were the requirements that it should be able to be built largely by unskilled labor, and that the wings should be foldable. This latter feature was not intended for potential use on aircraft carriers, but rather to enable the aircraft to be hidden in caves and tunnels around Japan as the navy began to prepare for the defense of the home islands.

 

Nakajima designers Kazuo Ohno and Kenichi Matsumura laid out an aircraft that bore a strong but superficial resemblance to the Me 262. Compared to the Me 262, the J9N airframe was noticeably smaller and more conventional in design, with straight wings and tail surfaces, lacking the slight sweepback of the Me 262. The triangular fuselage cross section characteristic of the German design was less pronounced, due to smaller fuel tanks. The main landing gear of the Kikka was taken from the A6M Zero and the nose wheel from the tail of a Yokosuka P1Y bomber.

The Kikka was designed in preliminary form to use the Tsu-11, a rudimentary motorjet style jet engine that was essentially a ducted fan with an afterburner. Subsequent designs were planned around the Ne-10 (TR-10) centrifugal-flow turbojet, and the Ne-12, which added a four-stage axial compressor to the front of the Ne-10. Tests of this powerplant soon revealed that it would not produce anywhere near the power required to propel the aircraft, and the project was temporarily stalled. It was then decided to produce a new axial flow turbojet based on the German BMW 003.

 

Development of the engine was troubled, based on little more than photographs and a single cut-away drawing of the BMW 003. A suitable unit, the Ishikawa-jima Ne-20, was finally built in January 1945. By that time, the Kikka project was making progress and the first prototype made its maiden flight. Due to the worsening war situation, the Navy considered employing the Kikka as a kamikaze weapon, but this was quickly rejected due to the high cost and complexity associated with manufacturing contemporary turbojet engines. Other more economical projects designed specifically for kamikaze attacks, such as the simpler Nakajima Tōka (designed to absorb Japanese stock of obsolete engines), the pulsejet-powered Kawanishi Baika, and the infamous Yokosuka Ohka, were either underway or already in mass production.

 

The following month the prototype was dismantled and delivered to Kisarazu Naval Airfield where it was re-assembled and prepared for flight testing. The aircraft performed well during a 20-minute test flight, with the only concern being the length of the takeoff run – the Ne 20 only had a thrust of 4.66 kN (1,047 lbf), and the engine pair had barely sufficient power to get the aircraft off the ground. This lack of thrust also resulted in a maximum speed of just 623 km/h (387 mph, 336 kn) at sea level and 696 km/h (432 mph; 376 kn) at 10,000 m (32,808 ft).

For the second test flight, four days later, rocket assisted take off (RATO) units were fitted to the aircraft, which worked and gave the aircraft acceptable field performance. The tests went on, together with a second prototype, but despite this early test stage, the J9N was immediately rushed into production.

 

By May 1945 approximately forty airframes had been completed and handed over to IJN home defense frontline units for operational use and conversion training. These were structurally identical with the prototypes, but they were powered by more potent and reliable Ne-130 (with 8.826 kN/900 kgf) or Ne-230 (8.679 kN/885 kgf) engines, which finally gave the aircraft a competitive performance and also made the RATO boosters obsolete - unless an 800 kg bomb was carried in overload configuration. Most were J9N1 day fighter single seaters, armed with two 30 mm Type 5 cannons with 50 rounds per gun in the nose. Some operational Kitsukas had, due to the lack of equipment, the 30 mm guns replaced with lighter 20 mm Ho-5 cannon. A few were unarmed two-seaters (J9N2) with dual controls and a second seat instead of the fuselage fuel tank. This markedly limited the aircraft’s range but was accepted for a dedicated trainer, but a ventral 500 l drop tank could be carried to extend the two-seater’s range to an acceptable level.

 

A small number, both single- and two-seaters, were furthermore adapted to night fighter duties and equipped with an experimental ”FD-2” centimeter waveband radar in the nose with an “antler” antenna array, similar to German radar sets of the time. The FD-2 used four forward-facing Yagi style antennae with initially five and later with seven elements (the sideway facing rods) each. These consisted of two pairs, each with a sending (top and bot) and a receiving antenna (left and right). The set used horizontal lobe switching to find the target, an electrical shifter would continuously switch between the sets. The signal strengths would then be compared to determine the range and azimuth of the target, and the results would then be shown on a CRT display.

 

In order to fit the electronics (the FD-2 weighed around 70 kg/155 lb) the night fighters typically had one of the nose-mounted guns replaced by a fixed, obliquely firing Ho-5 gun ("Schräge Musik"-style), which was mounted in the aircraft’s flank behind the cockpit, and the 500l drop tank became a permanent installation to extend loiter time, at the expense of top speed, though. These machines received the suffix “-S” and flew, despite the FD-2’s weaknesses and limitations, a few quite effective missions against American B-29 bombers, but their impact was minimal due to the aircrafts’ small numbers and poor reliability of the still experimental radar system. However, the FD-2’s performance was rather underwhelming, though, with an insufficient range of only 3 km. Increased drag due to the antennae and countermeasures deployed by B-29 further decreased the effectiveness, and the J9N2-S’s successes could be rather attributed to experienced and motivated crews than the primitive radar.

 

Proposed follow-on J9N versions had included a reconnaissance aircraft and a fast attack aircraft that was supposed to carry a single bomb under the fuselage against ships. There was also a modified version of the design to be launched from a 200 m long catapult, the "Nakajima Kikka-kai Prototype Turbojet Special Attacker". All these proposed versions were expected to be powered by more advanced developments of the Ne-20, the Ne-330 with 13 kN (1.330 kg) thrust, but none of them reached the hardware stage.

 

The J9Ns’ overall war contribution was negligible, and after the war, several airframes (including partial airframes) were captured by Allied forces. Three airframes (including a two-seat night fighter with FD-2 radar) were brought to the U.S. for study. Today, two J9N examples survive in the National Air and Space Museum: The first is a Kikka that was taken to the Patuxent River Naval Air Base, Maryland for analysis. This aircraft is very incomplete and is believed to have been patched together from a variety of semi-completed airframes. It is currently still in storage at the Paul E. Garber Preservation, Restoration and Storage Facility in Silver Hill, MD. The second Kikka is on display at the NASM Udvar-Hazy Center in the Mary Baker Engen Restoration Hangar.

  

General characteristics:

Crew: 2

Length: 8.13 m (26 ft 8 in) fuselage only

10.30 m (33 ft 8¾ in) with FD-2 antenna array

Wingspan: 10 m (32 ft 10 in)

Height: 2.95 m (9 ft 8 in)

Wing area: 13.2 m² (142 sq ft)

Empty weight: 2,300 kg (5,071 lb)

Gross weight: 3,500 kg (7,716 lb)

Max takeoff weight: 4,080 kg (8,995 lb)

 

Powerplant:

2× Ishikawajima Ne-130 or Ne-230 axial-flow turbojet engines

each with 8.83 kN/900 kg or 8.68 kN/885 kg thrust

 

Performance:

Maximum speed: 785 km/h (487 mph, 426 kn)

Range: 925 km (574 mi, 502 nmi) with internal fuel

Service ceiling: 12,000 m (39,000 ft)

Rate of climb: 10.5 m/s (2,064 ft/min)

Wing loading: 265 kg/m² (54 lb/sq ft)

Thrust-to-weight ratio: 0.43

 

Armament:

1× 30 mm (1.181 in) Type 5 cannon with 50 rounds in the nose

1× 20 mm (0.787 in) Type Ho-2 cannon with 80 rounds, mounted obliquely behind the cockpit

1× ventral hardpoint for a 500 l drop tank or a single 500 kg (1,102 lb) bomb

  

The kit and its assembly:

This is in fact the second Kikka I have built, and this time it’s a two-seater from AZ Models – actually the trainer boxing, but converted into a personal night fighter interpretation. The AZ Models kit is a simple affair, but that's also its problem. In the box things look quite good, detail level is on par with a classic Matchbox kit. But unlike a Matchbox kit, the AZ Models offering does not go together well. I had to fight everywhere with poor fit, lack of locator pins, ejection marks - anything a short run model kit can throw at you! Thanks to the experience with the single-seater kit some time ago, things did not become too traumatic, but it’s still not a kit for beginners. What worked surprisingly well was the IP canopy, though, which I cut into five sections for an optional open display – even though I am not certain if the kit’s designers had put some brain into their work because the canopy’s segmentation becomes more and more dubious the further you go backwards.

 

The only personal mods is a slightly changed armament, with one nose gun deleted and faired over with a piece of styrene sheet, while the leftover gun was mounted obliquely onto the left flank. I initially considered a position behind the canopy but rejected this because of CoG reasons. Then I planned to mount it directly behind the 2nd seat, so that the barrel would protrude through the canopy, but this appeared unrealistic because the (utterly tiny) sliding canopy for the rear crewman could not have been opened anymore? Finally, I settled for an offset position in the aircraft’s flanks, partly inspired by “Schräge Musik” arrangements on some German Fw 190 night fighters.

 

The antennae come from a Jadar Model PE set for Italeri’s Me 210s, turning it either into a night fighter or a naval surveillance aircraft.

  

Painting and markings:

This became rather lusterless; many late IJN night fighters carried a uniform dark green livery with minimalistic, toned-down markings, e. g. hinomaru without a white high-contrast edge, just the yellow ID bands on the wings’ leading edges were retained.

For this look the model received an overall basis coat of Humbrol 75 (Bronze Green), later treated with a black ink washing, dry-brushed aluminum and post-shading with lighter shades of dark green (including Humbrol 116 and Revell 67). The only colorful highlight is a red fin tip (Humbrol 19) and a thin red stripe underneath (decal). The yellow and white ID bands were created with decal material.

 

The cockpit interior was painted in a yellowish-green primer (trying to simulate a typical “bamboo” shade that was used in some late-war IJN cockpits), while the landing gear wells were painted in aodake iro, a clear bluish protective lacquer. The landing gear struts themselves became semi-matt black.

 

The markings are fictional and were puzzled together from various sources. The hinomaru came from the AZ Models’ Kikka single seater sheet (since it offers six roundels w/o white edge), the tactical code on the fin was created with red numbers from a Fujimi Aichi B7A2 Ryusei.

 

Finally, the kit received a coat of matt acrylic varnish and some grinded graphite around the jet exhausts and the gun nozzles.

  

Well, this fictional Kikka night fighter looks quite dry, but that makes it IMHO more credible. The large antler antenna array might look “a bit too much”, and a real night fighter probably had a simpler arrangement with a single Yagi-style/arrow-shaped antenna, but a description of the FD-2 radar suggested the layout I chose – and it does not look bad. The oblique cannon in the flank is another odd detail, but it is not unplausible. However, with all the equipment and esp. the draggy antennae on board, the Kikka’s mediocre performance would surely have seriously suffered, probably beyond an effective use. But this is whifworld, after all. ;-)

Three Legged Cross, Dorset

 

COLLEMBOLA (Springtails) > ENTOMOBRYOMORPHA > Entomobryidae > Orchesellinae > Orchesella villosa

____________________________________________________

 

Hidden Worlds

Whilst previously classified with insects, the COLLEMBOLA (Springtails) are now treated as a separate subclass with the other non-insect hexapods – DIPLURA (the Two-pronged Bristletails) and PROTURA (Proturans or Coneheads); all being grouped together into ENTOGNATHA, the class for wingless ARTHROPODS, that sits alongside INSECTA in the subphylum HEXAPODA.

 

{EDIT: see this photo for the current higher taxonomy in accordance with the comments below}

 

Springtails, the most abundant arthropods on earth, are very small wingless creatures, just a few millimetres long that live mainly in soil and leaf litter. They are so named due to their forked springing organ, or furca, which enables them to jump considerable distances of up to several centimetres when disturbed. They have reduced eyes, variable length antennae, simple bodies and short legs. They have two distinct forms; elongate in which the six abdomen segments are clearly visible, and globular bodies where the segmentation is far from apparent. There are around 250 species in Britain, the majority of which are so small that I wouldn’t even attempt to photograph them. However, there are a few in the 2-5mm range that are of interest and over the past few weeks I have managed to get some reasonable photos of some of them.

 

This is Orchesella villosa, one of the more common and widespread species. It is also one of the largest reaching 5mm in length.

 

Algorithmic Drive. Daïmôn. October 2018.

francois-quevillon.com/w/?p=1466

  

Conduite algorithmique. Daïmôn. Octobre 2018.

francois-quevillon.com/w/?p=1470&lang=fr

While wandering around office, my friend Venkataramanan found this little caterpillar, which was mimicking the neem flower petals. He invited me to capture the pics of this beauty!

 

Left side sequence (4 pictures): So, I placed a neem flower near it and watched its moves. It swayed based on the breeze force as though it is a petal of the neem flower.

 

Right side picture: Then he started to move one step showcasing that he is a true caterpillar after all!

 

Thanks to Venkat for getting me this nice natural history sequence and appreciate his eyes for spotting this!

 

Since this tiny insect might be confused with leech, due to its similar motion, thought of penning down some points. This is a caterpillar and not a leech for the following reasons:

 

(1) Leeches do not have legs. They only have suction cups at either ends. This fellow had at least 3 pairs of legs near head (anterior) and 2 pairs near the posterior base - take a close look at the right side image!

 

(2) Leeches belong to Phylum Annelida (meaning little rings as bodies), while caterpillars are insects and belong to Phylum Arthropoda (meaning jointed legs) and Class Insecta, which are young ones of moths/butterflies.

 

(3) Also, caterpillars move in a characteristic U motion with both ends lying on ground firmly (check right side of picture), while leeches do have a V motion where only tips of each end touches ground for locomotion!

 

(4) Leeches are found only in humid areas like Munnar/Kodai/Ooty or near water bodies if in Chennai, not in dry / arid areas.

 

(5) The body segmentation is very significant in leeches (well sequenced rings), wherein caterpillars do not have such demarcation, though they have distinct coloration patterns.

 

(6) One common thing of both leeches and caterpillars is not to touch them. Leeches may stick and start to suck blood and Caterpillars have toxins on their body surface that may cause irritation and pain in skin of sensitive people.

Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms. Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. As of November 2015, at least 45,700 spider species, and 114 families have been recorded by taxonomists. However, there has been dissension within the scientific community as to how all these families should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.

 

Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.

 

Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appeared in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets. True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving suborder, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before 200 million years ago.

 

A herbivorous species, Bagheera kiplingi, was described in 2008,[5] but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, and they liquefy their food by flooding it with digestive enzymes and grinding it with the bases of their pedipalps, as they do not have true jaws.

 

Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity.

 

While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers. An abnormal fear of spiders is called arachnophobia.

 

BODY PLAN

Spiders are chelicerates and therefore arthropods.[6] As arthropods they have: segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo. Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the cephalothorax or prosoma, is a complete fusion of the segments that in an insect would form two separate tagmata, the head and thorax; the rear tagma is called the abdomen or opisthosoma. In spiders, the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel. The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods. In fact, chelicerates' only appendages ahead of the mouth are a pair of chelicerae, and they lack anything that would function directly as "jaws". The first appendages behind the mouth are called pedipalps, and serve different functions within different groups of chelicerates.

 

Spiders and scorpions are members of one chelicerate group, the arachnids. Scorpions' chelicerae have three sections and are used in feeding. Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use. The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food.[8] Scorpions' pedipalps generally form large claws for capturing prey, while those of spiders are fairly small appendages whose bases also act as an extension of the mouth; in addition, those of male spiders have enlarged last sections used for sperm transfer.

 

In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk. The upper surface of the cephalothorax is covered by a single, convex carapace, while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface.

 

CIRCULATION AND RESPIRATION

Like other arthropods, spiders are coelomates in which the coelom is reduced to small areas round the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows. The heart is a tube in the upper part of the body, with a few ostia that act as non-return valves allowing blood to enter the heart from the hemocoel but prevent it from leaving before it reaches the front end. However, in spiders, it occupies only the upper part of the abdomen, and blood is discharged into the hemocoel by one artery that opens at the rear end of the abdomen and by branching arteries that pass through the pedicle and open into several parts of the cephalothorax. Hence spiders have open circulatory systems. The blood of many spiders that have book lungs contains the respiratory pigment hemocyanin to make oxygen transport more efficient.

 

Spiders have developed several different respiratory anatomies, based on book lungs, a tracheal system, or both. Mygalomorph and Mesothelae spiders have two pairs of book lungs filled with haemolymph, where openings on the ventral surface of the abdomen allow air to enter and diffuse oxygen. This is also the case for some basal araneomorph spiders, like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs. The trachea system has most likely evolved in small ancestors to help resist desiccation. The trachea were originally connected to the surroundings through a pair of openings called spiracles, but in the majority of spiders this pair of spiracles has fused into a single one in the middle, and moved backwards close to the spinnerets. Spiders that have tracheae generally have higher metabolic rates and better water conservation. Spiders are ectotherms, so environmental temperatures affect their activity.

 

FEEDING, DIGESTION AND EXCRETION

Uniquely among chelicerates, the final sections of spiders' chelicerae are fangs, and the great majority of spiders can use them to inject venom into prey from venom glands in the roots of the chelicerae. The family Uloboridae has lost its venom glands, and kills its prey with silk instead. Like most arachnids, including scorpions, spiders have a narrow gut that can only cope with liquid food and spiders have two sets of filters to keep solids out. They use one of two different systems of external digestion. Some pump digestive enzymes from the midgut into the prey and then suck the liquified tissues of the prey into the gut, eventually leaving behind the empty husk of the prey. Others grind the prey to pulp using the chelicerae and the bases of the pedipalps, while flooding it with enzymes; in these species, the chelicerae and the bases of the pedipalps form a preoral cavity that holds the food they are processing.

 

The stomach in the cephalothorax acts as a pump that sends the food deeper into the digestive system. The mid gut bears many digestive ceca, compartments with no other exit, that extract nutrients from the food; most are in the abdomen, which is dominated by the digestive system, but a few are found in the cephalothorax.

 

Most spiders convert nitrogenous waste products into uric acid, which can be excreted as a dry material. Malphigian tubules ("little tubes") extract these wastes from the blood in the hemocoel and dump them into the cloacal chamber, from which they are expelled through the anus. Production of uric acid and its removal via Malphigian tubules are a water-conserving feature that has evolved independently in several arthropod lineages that can live far away from water, for example the tubules of insects and arachnids develop from completely different parts of the embryo. However, a few primitive spiders, the sub-order Mesothelae and infra-order Mygalomorphae, retain the ancestral arthropod nephridia ("little kidneys"), which use large amounts of water to excrete nitrogenous waste products as ammonia.

 

CENTRAL NERVOUS SYSTEM

The basic arthropod central nervous system consists of a pair of nerve cords running below the gut, with paired ganglia as local control centers in all segments; a brain formed by fusion of the ganglia for the head segments ahead of and behind the mouth, so that the esophagus is encircled by this conglomeration of ganglia. Except for the primitive Mesothelae, of which the Liphistiidae are the sole surviving family, spiders have the much more centralized nervous system that is typical of arachnids: all the ganglia of all segments behind the esophagus are fused, so that the cephalothorax is largely filled with nervous tissue and there are no ganglia in the abdomen; in the Mesothelae, the ganglia of the abdomen and the rear part of the cephalothorax remain unfused.

 

Despite the relatively small central nervous system, some spiders (like Portia) exhibit complex behaviour, including the ability to use a trial-and-error approach.

Sense organs

 

EYES

Most spiders have four pairs of eyes on the top-front area of the cephalothorax, arranged in patterns that vary from one family to another. The pair at the front are of the type called pigment-cup ocelli ("little eyes"), which in most arthropods are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup. However, the main eyes at the front of spiders' heads are pigment-cup ocelli that are capable of forming images. The other eyes are thought to be derived from the compound eyes of the ancestral chelicerates, but no longer have the separate facets typical of compound eyes. Unlike the main eyes, in many spiders these secondary eyes detect light reflected from a reflective tapetum lucidum, and wolf spiders can be spotted by torch light reflected from the tapeta. On the other hand, jumping spiders' secondary eyes have no tapeta. Some jumping spiders' visual acuity exceeds by a factor of ten that of dragonflies, which have by far the best vision among insects; in fact the human eye is only about five times sharper than a jumping spider's. They achieve this by a telephoto-like series of lenses, a four-layer retina and the ability to swivel their eyes and integrate images from different stages in the scan. The downside is that the scanning and integrating processes are relatively slow.

 

There are spiders with a reduced number of eyes, of these those with six-eyes are the most numerous and are missing a pair of eyes on the anterior median line, others species have four-eyes and some just two. Cave dwelling species have no eyes, or possess vestigial eyes incapable of sight.

 

OTHER SENSES

As with other arthropods, spiders' cuticles would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly bristles called setae, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell, often by means of setae. Pedipalps carry a large number of such setae sensitive to contact chemicals and air-borne smells, such as female pheromones. Spiders also have in the joints of their limbs slit sensillae that detect forces and vibrations. In web-building spiders, all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively.

 

Like most arthropods, spiders lack balance and acceleration sensors and rely on their eyes to tell them which way is up. Arthropods' proprioceptors, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well understood. On the other hand, little is known about what other internal sensors spiders or other arthropods may have.

 

LOCMOTION

Each of the eight legs of a spider consists of seven distinct parts. The part closest to and attaching the leg to the cephalothorax is the coxa; the next segment is the short trochanter that works as a hinge for the following long segment, the femur; next is the spider's knee, the patella, which acts as the hinge for the tibia; the metatarsus is next, and it connects the tibia to the tarsus (which may be thought of as a foot of sorts); the tarsus ends in a claw made up of either two or three points, depending on the family to which the spider belongs. Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, spiders and a few other groups still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors. The only extensor muscles in spider legs are located in the three hip joints (bordering the coxa and the trochanter). As a result, a spider with a punctured cephalothorax cannot extend its legs, and the legs of dead spiders curl up. Spiders can generate pressures up to eight times their resting level to extend their legs, and jumping spiders can jump up to 50 times their own length by suddenly increasing the blood pressure in the third or fourth pair of legs. Although larger spiders use hydraulics to straighten their legs, unlike smaller jumping spiders they depend on their flexor muscles to generate the propulsive force for their jumps.

 

Most spiders that hunt actively, rather than relying on webs, have dense tufts of fine hairs between the paired claws at the tips of their legs. These tufts, known as scopulae, consist of bristles whose ends are split into as many as 1,000 branches, and enable spiders with scopulae to walk up vertical glass and upside down on ceilings. It appears that scopulae get their grip from contact with extremely thin layers of water on surfaces.[8] Spiders, like most other arachnids, keep at least four legs on the surface while walking or running.

 

SILK PRODUCTION

The abdomen has no appendages except those that have been modified to form one to four (usually three) pairs of short, movable spinnerets, which emit silk. Each spinneret has many spigots, each of which is connected to one silk gland. There are at least six types of silk gland, each producing a different type of silk.

 

Silk is mainly composed of a protein very similar to that used in insect silk. It is initially a liquid, and hardens not by exposure to air but as a result of being drawn out, which changes the internal structure of the protein. It is similar in tensile strength to nylon and biological materials such as chitin, collagen and cellulose, but is much more elastic. In other words, it can stretch much further before breaking or losing shape.

 

Some spiders have a cribellum, a modified spinneret with up to 40,000 spigots, each of which produces a single very fine fiber. The fibers are pulled out by the calamistrum, a comb-like set of bristles on the jointed tip of the cribellum, and combined into a composite woolly thread that is very effective in snagging the bristles of insects. The earliest spiders had cribella, which produced the first silk capable of capturing insects, before spiders developed silk coated with sticky droplets. However, most modern groups of spiders have lost the cribellum.

 

Tarantulas also have silk glands in their feet.

 

Even species that do not build webs to catch prey use silk in several ways: as wrappers for sperm and for fertilized eggs; as a "safety rope"; for nest-building; and as "parachutes" by the young of some species.

 

REPRODUCTION AND LIFE CYCLE

Spiders reproduce sexually and fertilization is internal but indirect, in other words the sperm is not inserted into the female's body by the male's genitals but by an intermediate stage. Unlike many land-living arthropods, male spiders do not produce ready-made spermatophores (packages of sperm), but spin small sperm webs on to which they ejaculate and then transfer the sperm to special syringe-like structures, palpal bulbs or palpal organs, borne on the tips of the pedipalps of mature males. When a male detects signs of a female nearby he checks whether she is of the same species and whether she is ready to mate; for example in species that produce webs or "safety ropes", the male can identify the species and sex of these objects by "smell".

 

Spiders generally use elaborate courtship rituals to prevent the large females from eating the small males before fertilization, except where the male is so much smaller that he is not worth eating. In web-weaving species, precise patterns of vibrations in the web are a major part of the rituals, while patterns of touches on the female's body are important in many spiders that hunt actively, and may "hypnotize" the female. Gestures and dances by the male are important for jumping spiders, which have excellent eyesight. If courtship is successful, the male injects his sperm from the palpal bulbs into the female's genital opening, known as the epigyne, on the underside of her abdomen. Female's reproductive tracts vary from simple tubes to systems that include seminal receptacles in which females store sperm and release it when they are ready.

 

Males of the genus Tidarren amputate one of their palps before maturation and enter adult life with one palp only. The palps are 20% of male's body mass in this species, and detaching one of the two improves mobility. In the Yemeni species Tidarren argo, the remaining palp is then torn off by the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime, the female feeds on the palpless male. In over 60% of cases, the female of the Australian redback spider kills and eats the male after it inserts its second palp into the female's genital opening; in fact, the males co-operate by trying to impale themselves on the females' fangs. Observation shows that most male redbacks never get an opportunity to mate, and the "lucky" ones increase the likely number of offspring by ensuring that the females are well-fed. However, males of most species survive a few matings, limited mainly by their short life spans. Some even live for a while in their mates' webs.

 

Females lay up to 3,000 eggs in one or more silk egg sacs, which maintain a fairly constant humidity level. In some species, the females die afterwards, but females of other species protect the sacs by attaching them to their webs, hiding them in nests, carrying them in the chelicerae or attaching them to the spinnerets and dragging them along.

 

Baby spiders pass all their larval stages inside the egg and hatch as spiderlings, very small and sexually immature but similar in shape to adults. Some spiders care for their young, for example a wolf spider's brood cling to rough bristles on the mother's back, and females of some species respond to the "begging" behaviour of their young by giving them their prey, provided it is no longer struggling, or even regurgitate food.

 

Like other arthropods, spiders have to molt to grow as their cuticle ("skin") cannot stretch. In some species males mate with newly molted females, which are too weak to be dangerous to the males. Most spiders live for only one to two years, although some tarantulas can live in captivity for over 20 years.

 

SIZE

Spiders occur in a large range of sizes. The smallest, Patu digua from Colombia, are less than 0.37 mm in body length. The largest and heaviest spiders occur among tarantulas, which can have body lengths up to 90 mm and leg spans up to 250 mm.

 

COLORATION

Only three classes of pigment (ommochromes, bilins and guanine) have been identified in spiders, although other pigments have been detected but not yet characterized. Melanins, carotenoids and pterins, very common in other animals, are apparently absent. In some species, the exocuticle of the legs and prosoma is modified by a tanning process, resulting in brown coloration. Bilins are found, for example, in Micrommata virescens, resulting in its green color. Guanine is responsible for the white markings of the European garden spider Araneus diadematus. It is in many species accumulated in specialized cells called guanocytes. In genera such as Tetragnatha, Leucauge, Argyrodes or Theridiosoma, guanine creates their silvery appearance. While guanine is originally an end-product of protein metabolism, its excretion can be blocked in spiders, leading to an increase in its storage. Structural colors occur in some species, which are the result of the diffraction, scattering or interference of light, for example by modified setae or scales. The white prosoma of Argiope results from hairs reflecting the light, Lycosa and Josa both have areas of modified cuticle that act as light reflectors.

 

ECOGOGY AND BEHAVIOR

NON-PREDATORY FEEDING

Although spiders are generally regarded as predatory, the jumping spider Bagheera kiplingi gets over 90% of its food from fairly solid plant material produced by acacias as part of a mutually beneficial relationship with a species of ant.

 

Juveniles of some spiders in the families Anyphaenidae, Corinnidae, Clubionidae, Thomisidae and Salticidae feed on plant nectar. Laboratory studies show that they do so deliberately and over extended periods, and periodically clean themselves while feeding. These spiders also prefer sugar solutions to plain water, which indicates that they are seeking nutrients. Since many spiders are nocturnal, the extent of nectar consumption by spiders may have been underestimated. Nectar contains amino acids, lipids, vitamins and minerals in addition to sugars, and studies have shown that other spider species live longer when nectar is available. Feeding on nectar avoids the risks of struggles with prey, and the costs of producing venom and digestive enzymes.

 

Various species are known to feed on dead arthropods (scavenging), web silk, and their own shed exoskeletons. Pollen caught in webs may also be eaten, and studies have shown that young spiders have a better chance of survival if they have the opportunity to eat pollen. In captivity, several spider species are also known to feed on bananas, marmalade, milk, egg yolk and sausages.

 

METHODS OF CAPTURING PREY

The best-known method of prey capture is by means of sticky webs. Varying placement of webs allows different species of spider to trap different insects in the same area, for example flat horizontal webs trap insects that fly up from vegetation underneath while flat vertical webs trap insects in horizontal flight. Web-building spiders have poor vision, but are extremely sensitive to vibrations.

 

Females of the water spider Argyroneta aquatica build underwater "diving bell" webs that they fill with air and use for digesting prey, molting, mating and raising offspring. They live almost entirely within the bells, darting out to catch prey animals that touch the bell or the threads that anchor it. A few spiders use the surfaces of lakes and ponds as "webs", detecting trapped insects by the vibrations that these cause while struggling.

 

Net-casting spiders weave only small webs, but then manipulate them to trap prey. Those of the genus Hyptiotes and the family Theridiosomatidae stretch their webs and then release them when prey strike them, but do not actively move their webs. Those of the family Deinopidae weave even smaller webs, hold them outstretched between their first two pairs of legs, and lunge and push the webs as much as twice their own body length to trap prey, and this move may increase the webs' area by a factor of up to ten. Experiments have shown that Deinopis spinosus has two different techniques for trapping prey: backwards strikes to catch flying insects, whose vibrations it detects; and forward strikes to catch ground-walking prey that it sees. These two techniques have also been observed in other deinopids. Walking insects form most of the prey of most deinopids, but one population of Deinopis subrufa appears to live mainly on tipulid flies that they catch with the backwards strike.

 

Mature female bolas spiders of the genus Mastophora build "webs" that consist of only a single "trapeze line", which they patrol. They also construct a bolas made of a single thread, tipped with a large ball of very wet sticky silk. They emit chemicals that resemble the pheromones of moths, and then swing the bolas at the moths. Although they miss on about 50% of strikes, they catch about the same weight of insects per night as web-weaving spiders of similar size. The spiders eat the bolas if they have not made a kill in about 30 minutes, rest for a while, and then make new bolas. Juveniles and adult males are much smaller and do not make bolas. Instead they release different pheromones that attract moth flies, and catch them with their front pairs of legs.

 

The primitive Liphistiidae, the "trapdoor spiders" of the family Ctenizidae and many tarantulas are ambush predators that lurk in burrows, often closed by trapdoors and often surrounded by networks of silk threads that alert these spiders to the presence of prey. Other ambush predators do without such aids, including many crab spiders, and a few species that prey on bees, which see ultraviolet, can adjust their ultraviolet reflectance to match the flowers in which they are lurking. Wolf spiders, jumping spiders, fishing spiders and some crab spiders capture prey by chasing it, and rely mainly on vision to locate prey.Some jumping spiders of the genus Portia hunt other spiders in ways that seem intelligent, outflanking their victims or luring them from their webs. Laboratory studies show that Portia's instinctive tactics are only starting points for a trial-and-error approach from which these spiders learn very quickly how to overcome new prey species. However, they seem to be relatively slow "thinkers", which is not surprising, as their brains are vastly smaller than those of mammalian predators.Ant-mimicking spiders face several challenges: they generally develop slimmer abdomens and false "waists" in the cephalothorax to mimic the three distinct regions (tagmata) of an ant's body; they wave the first pair of legs in front of their heads to mimic antennae, which spiders lack, and to conceal the fact that they have eight legs rather than six; they develop large color patches round one pair of eyes to disguise the fact that they generally have eight simple eyes, while ants have two compound eyes; they cover their bodies with reflective hairs to resemble the shiny bodies of ants. In some spider species, males and females mimic different ant species, as female spiders are usually much larger than males. Ant-mimicking spiders also modify their behavior to resemble that of the target species of ant; for example, many adopt a zig-zag pattern of movement, ant-mimicking jumping spiders avoid jumping, and spiders of the genus Synemosyna walk on the outer edges of leaves in the same way as Pseudomyrmex. Ant-mimicry in many spiders and other arthropods may be for protection from predators that hunt by sight, including birds, lizards and spiders. However, several ant-mimicking spiders prey either on ants or on the ants' "livestock", such as aphids. When at rest, the ant-mimicking crab spider Amyciaea does not closely resemble Oecophylla, but while hunting it imitates the behavior of a dying ant to attract worker ants. After a kill, some ant-mimicking spiders hold their victims between themselves and large groups of ants to avoid being attacked.

 

DEFENSE

There is strong evidence that spiders' coloration is camouflage that helps them to evade their major predators, birds and parasitic wasps, both of which have good color vision. Many spider species are colored so as to merge with their most common backgrounds, and some have disruptive coloration, stripes and blotches that break up their outlines. In a few species, such as the Hawaiian happy-face spider, Theridion grallator, several coloration schemes are present in a ratio that appears to remain constant, and this may make it more difficult for predators to recognize the species. Most spiders are insufficiently dangerous or unpleasant-tasting for warning coloration to offer much benefit. However, a few species with powerful venoms, large jaws or irritant hairs have patches of warning colors, and some actively display these colors when threatened.

 

Many of the family Theraphosidae, which includes tarantulas and baboon spiders, have urticating hairs on their abdomens and use their legs to flick them at attackers. These hairs are fine setae (bristles) with fragile bases and a row of barbs on the tip. The barbs cause intense irritation but there is no evidence that they carry any kind of venom. A few defend themselves against wasps by including networks of very robust threads in their webs, giving the spider time to flee while the wasps are struggling with the obstacles. The golden wheeling spider, Carparachne aureoflava, of the Namibian desert escapes parasitic wasps by flipping onto its side and cartwheeling down sand dunes.

 

SOCIAL SPIDERS

A few spider species that build webs live together in large colonies and show social behavior, although not as complex as in social insects. Anelosimus eximius (in the family Theridiidae) can form colonies of up to 50,000 individuals. The genus Anelosimus has a strong tendency towards sociality: all known American species are social, and species in Madagascar are at least somewhat social. Members of other species in the same family but several different genera have independently developed social behavior. For example, although Theridion nigroannulatum belongs to a genus with no other social species, T. nigroannulatum build colonies that may contain several thousand individuals that co-operate in prey capture and share food. Other communal spiders include several Philoponella species (family Uloboridae), Agelena consociata (family Agelenidae) and Mallos gregalis (family Dictynidae). Social predatory spiders need to defend their prey against kleptoparasites ("thieves"), and larger colonies are more successful in this. The herbivorous spider Bagheera kiplingi lives in small colonies which help to protect eggs and spiderlings. Even widow spiders (genus Latrodectus), which are notoriously cannibalistic, have formed small colonies in captivity, sharing webs and feeding together.

 

WEB TYPES

There is no consistent relationship between the classification of spiders and the types of web they build: species in the same genus may build very similar or significantly different webs. Nor is there much correspondence between spiders' classification and the chemical composition of their silks. Convergent evolution in web construction, in other words use of similar techniques by remotely related species, is rampant. Orb web designs and the spinning behaviors that produce them are the best understood. The basic radial-then-spiral sequence visible in orb webs and the sense of direction required to build them may have been inherited from the common ancestors of most spider groups. However, the majority of spiders build non-orb webs. It used to be thought that the sticky orb web was an evolutionary innovation resulting in the diversification of the Orbiculariae. Now, however, it appears that non-orb spiders are a sub-group that evolved from orb-web spiders, and non-orb spiders have over 40% more species and are four times as abundant as orb-web spiders. Their greater success may be because sphecid wasps, which are often the dominant predators of spiders, much prefer to attack spiders that have flat webs.

 

ORB WEBS

About half the potential prey that hit orb webs escape. A web has to perform three functions: intercepting the prey (intersection), absorbing its momentum without breaking (stopping), and trapping the prey by entangling it or sticking to it (retention). No single design is best for all prey. For example: wider spacing of lines will increase the web's area and hence its ability to intercept prey, but reduce its stopping power and retention; closer spacing, larger sticky droplets and thicker lines would improve retention, but would make it easier for potential prey to see and avoid the web, at least during the day. However, there are no consistent differences between orb webs built for use during the day and those built for use at night. In fact, there is no simple relationship between orb web design features and the prey they capture, as each orb-weaving species takes a wide range of prey.

 

The hubs of orb webs, where the spiders lurk, are usually above the center, as the spiders can move downwards faster than upwards. If there is an obvious direction in which the spider can retreat to avoid its own predators, the hub is usually offset towards that direction.

 

Horizontal orb webs are fairly common, despite being less effective at intercepting and retaining prey and more vulnerable to damage by rain and falling debris. Various researchers have suggested that horizontal webs offer compensating advantages, such as reduced vulnerability to wind damage; reduced visibility to prey flying upwards, because of the back-lighting from the sky; enabling oscillations to catch insects in slow horizontal flight. However, there is no single explanation for the common use of horizontal orb webs.

 

Spiders often attach highly visible silk bands, called decorations or stabilimenta, to their webs. Field research suggests that webs with more decorative bands captured more prey per hour. However, a laboratory study showed that spiders reduce the building of these decorations if they sense the presence of predators.

 

There are several unusual variants of orb web, many of them convergently evolved, including: attachment of lines to the surface of water, possibly to trap insects in or on the surface; webs with twigs through their centers, possibly to hide the spiders from predators; "ladder-like" webs that appear most effective in catching moths. However, the significance of many variations is unclear.

 

In 1973, Skylab 3 took two orb-web spiders into space to test their web-spinning capabilities in zero gravity. At first, both produced rather sloppy webs, but they adapted quickly.

 

TANGLEWEB SPIDERS (COBWEB SPIDERS)

Members of the family Theridiidae weave irregular, tangled, three-dimensional webs, popularly known as cobwebs. There seems to be an evolutionary trend towards a reduction in the amount of sticky silk used, leading to its total absence in some species. The construction of cobwebs is less stereotyped than that of orb-webs, and may take several days.

 

OTHER TYPES OF WEBS

The Linyphiidae generally make horizontal but uneven sheets, with tangles of stopping threads above. Insects that hit the stopping threads fall onto the sheet or are shaken onto it by the spider, and are held by sticky threads on the sheet until the spider can attack from below.

 

EVOLUTION

FOSSIL RECORD

Although the fossil record of spiders is considered poor, almost 1000 species have been described from fossils. Because spiders' bodies are quite soft, the vast majority of fossil spiders have been found preserved in amber. The oldest known amber that contains fossil arthropods dates from 130 million years ago in the Early Cretaceous period. In addition to preserving spiders' anatomy in very fine detail, pieces of amber show spiders mating, killing prey, producing silk and possibly caring for their young. In a few cases, amber has preserved spiders' egg sacs and webs, occasionally with prey attached; the oldest fossil web found so far is 100 million years old. Earlier spider fossils come from a few lagerstätten, places where conditions were exceptionally suited to preserving fairly soft tissues.

 

The oldest known exclusively terrestrial arachnid is the trigonotarbid Palaeotarbus jerami, from about 420 million years ago in the Silurian period, and had a triangular cephalothorax and segmented abdomen, as well as eight legs and a pair of pedipalps. Attercopus fimbriunguis, from 386 million years ago in the Devonian period, bears the earliest known silk-producing spigots, and was therefore hailed as a spider at the time of its discovery. However, these spigots may have been mounted on the underside of the abdomen rather than on spinnerets, which are modified appendages and whose mobility is important in the building of webs. Hence Attercopus and the similar Permian arachnid Permarachne may not have been true spiders, and probably used silk for lining nests or producing egg-cases rather than for building webs. The largest known fossil spider as of 2011 is the araneid Nephila jurassica, from about 165 million years ago, recorded from Daohuogo, Inner Mongolia in China. Its body length is almost 25 mm.

 

Several Carboniferous spiders were members of the Mesothelae, a primitive group now represented only by the Liphistiidae. The mesothelid Paleothele montceauensis, from the Late Carboniferous over 299 million years ago, had five spinnerets. Although the Permian period 299 to 251 million years ago saw rapid diversification of flying insects, there are very few fossil spiders from this period.

 

The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the Triassic well before 200 million years ago. Some Triassic mygalomorphs appear to be members of the family Hexathelidae, whose modern members include the notorious Sydney funnel-web spider, and their spinnerets appear adapted for building funnel-shaped webs to catch jumping insects. Araneomorphae account for the great majority of modern spiders, including those that weave the familiar orb-shaped webs. The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families.

 

WIKIPEDIA

(@Orly Airport)

People Counter

The People Counter determines the number of people within a specific area and detects their direction of movement.

Thanks to the 3D MLI SensorTM technology and its unique tracking and segmentation ability, the People Counter delivers real-time data, thereby enabling the following people counting applications:

Occupancy monitoring to control maximum or minimum occupancy, support evacuation measures and trigger demand-controlled ventilation (DCV)

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Flow monitoring

The new alltours head office building in Düsseldorf stands prominently on the Mannesmannufer, directly on the banks of the Rhine. Designed by HPP Architects, this significant new build aims to be a harmonious addition to its prestigious surroundings, nestled between the historic Behrensbau and the Mannesmann Tower. The building, completed around the first quarter of 2023, is a multi-functional ensemble, featuring not only modern office spaces for alltours but also freehold apartments, retirement housing, and a nursing and care facility, contributing to a vibrant mixed-use urban quarter.

 

Architecturally, the alltours headquarters is characterized by its elegant and finely structured facade. It features a vertical segmentation made of stone pilaster strips, creating a distinct yet calm architectural language. This design subtly references the nearby Behrensbau, with recurring "floor packages" and vertical window divisions. The main office building, spanning approximately 13,500 square meters over several floors (reportedly up to 10 or 11, with 2 underground), is designed with high transparency to maximize views of the Rhine and integrate naturally into the cityscape.

 

Inside, the building prioritizes a positive working environment and sustainability. A central, light-flooded atrium serves as the heart of the complex, offering generous communication and meeting zones. One of its most striking features is a massive 28-meter-high indoor green wall, considered one of Europe's largest, featuring over 5,600 plants. This vertical garden not only enhances the aesthetics but also contributes to air purification and a pleasant microclimate. The building also incorporates modern amenities such as a fitness area, chill-out zone, and employee restaurant with an outdoor terrace on the top floor, along with sustainable features like an intelligent energy concept and advanced cooling systems for year-round comfort.

Abstract

To understand the evolutionary significance of geographic variation, one must identify the factors that generate phenotypic differences among populations. I examined the causes of geographic variation in and evolutionary history of number of trunk vertebrae in slender salamanders. Batrachoseps (Caudata: Plethodontidae). Number of trunk vertebrae varies at many taxonomic levels within Batrachoseps. Parallel clines in number occur along an environmental gradient in three lineages in the Coast Ranges of California. These parallel clines may signal either adaptation or a shared phenotypically plastic response to the environmental gradient. By raising eggs from 10 populations representing four species of Batrachoseps, I demonstrated that number of trunk vertebrae can be altered by the developmental temperature; however, the degree of plasticity is insufficient to account for geographic variation. Thus, the geographic variation results largely from genetic variation. Number of trunk vertebrae covaries with body size and shape in diverse vertebrate taxa, including Batrachoseps. I hypothesize that selection for different degrees of elongation, possibly related to fossoriality, has led to the extensive evolution of number of trunk vertebrae in Batrachoseps. Analysis of intrapopulational variation revealed sexual dimorphism in both body shape and number of trunk vertebrae, but no correlation between these variables in either sex. Females are more elongate than males, a pattern that has been attributed to fecundity selection in other taxa. Patterns of covariation among different classes of vertebrae suggest that some intrapopulational variation in number results from changes in vertebral identity rather than changes in segmentation.

Elizabeth L. Jockusch

Evolution

 

MORE INFORMATION

 

Images in this gallery were captured by:

 

Mark Smith M.S. Geoscientist mark@macroscopicsolutions.com

 

Daniel Saftner B.S. Geoscientist and Returned Peace Corps Volunteer daniel@macroscopicsolutions.com

 

Annette Evans Ph.D. Student at the University of Connecticut annette@macroscopicsolutions.com

Three Legged Cross, Dorset

 

COLLEMBOLA (Springtails) > ENTOMOBRYOMORPHA >

Tomoceridae > Tomocerus cf. minor

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Hidden Worlds

COLLEMBOLA were previously classified with insects, but are now treated as a class in their own right, sitting alongside DIPLURA (the Two-pronged Bristletails) and PROTURA (Proturans or Coneheads). They are the wingless ARTHROPODS, which together with INSECTA are the four classes within the superclass HEXAPODA.

 

Springtails, the most abundant arthropods on earth, are very small wingless creatures, just a few millimetres long that live mainly in soil and leaf litter. They are so named due to their forked springing organ, or furca, which enables them to jump considerable distances of up to several centimetres when disturbed. They have reduced eyes, variable length antennae, simple bodies and short legs. They have two distinct forms; elongate in which the six abdomen segments are clearly visible, and globular bodies where the segmentation is far from apparent. There are around 250 species in Britain, the majority of which are so small that I wouldn’t even attempt to photograph them. However, there are a few in the 2-5mm range that are of interest and over the past few weeks I have managed to get some reasonable photos of some of them.

 

This Tomocerus species is closely related Pogonognathellus. It can grow to around 4.5mm and normally has a characteristic uniform silvery-bluish iridescence but, as with all the species in this family, their scales are easily shed giving pale-coloured specimens. There are three very similar Tomocerus species in Britain, which can only be definitively identified by microscopic examination. However, one of those species is not that common in the South West and another is a rare montane species and, consequently, it is very likely that the species I’ve seen and photographed is Tomocerus minor.

 

. . . looks like this spider knows how to write . . .

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Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms. Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. As of November 2015, at least 45,700 spider species, and 113 families have been recorded by taxonomists. However, there has been dissension within the scientific community as to how all these families should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.

 

Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.

 

Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appeared in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets. True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving suborder, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before 200 million years ago.

 

A herbivorous species, Bagheera kiplingi, was described in 2008, but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. It is estimated that 25 million tons of spiders kill 400–800 million tons of prey per year. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, and they liquefy their food by flooding it with digestive enzymes. They also grind food with the bases of their pedipalps, as arachnids do not have the mandibles that crustaceans and insects have.

 

Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity.

 

While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers. An abnormal fear of spiders is called arachnophobia.

 

DESCRIPTION

BODY PLAN

Spiders are chelicerates and therefore arthropods. As arthropods they have: segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo. Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the cephalothorax or prosoma, is a complete fusion of the segments that in an insect would form two separate tagmata, the head and thorax; the rear tagma is called the abdomen or opisthosoma. In spiders, the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel. The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods. In fact, chelicerates' only appendages ahead of the mouth are a pair of chelicerae, and they lack anything that would function directly as "jaws". The first appendages behind the mouth are called pedipalps, and serve different functions within different groups of chelicerates.

 

Spiders and scorpions are members of one chelicerate group, the arachnids. Scorpions' chelicerae have three sections and are used in feeding. Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use. The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food. Scorpions' pedipalps generally form large claws for capturing prey, while those of spiders are fairly small appendages whose bases also act as an extension of the mouth; in addition, those of male spiders have enlarged last sections used for sperm transfer.

 

In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk. The upper surface of the cephalothorax is covered by a single, convex carapace, while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface

 

CIRCULATION AND RESPIRATION

Like other arthropods, spiders are coelomates in which the coelom is reduced to small areas round the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows. The heart is a tube in the upper part of the body, with a few ostia that act as non-return valves allowing blood to enter the heart from the hemocoel but prevent it from leaving before it reaches the front end. However, in spiders, it occupies only the upper part of the abdomen, and blood is discharged into the hemocoel by one artery that opens at the rear end of the abdomen and by branching arteries that pass through the pedicle and open into several parts of the cephalothorax. Hence spiders have open circulatory systems. The blood of many spiders that have book lungs contains the respiratory pigment hemocyanin to make oxygen transport more efficient.

 

Spiders have developed several different respiratory anatomies, based on book lungs, a tracheal system, or both. Mygalomorph and Mesothelae spiders have two pairs of book lungs filled with haemolymph, where openings on the ventral surface of the abdomen allow air to enter and diffuse oxygen. This is also the case for some basal araneomorph spiders, like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs. The trachea system has most likely evolved in small ancestors to help resist desiccation. The trachea were originally connected to the surroundings through a pair of openings called spiracles, but in the majority of spiders this pair of spiracles has fused into a single one in the middle, and moved backwards close to the spinnerets. Spiders that have tracheae generally have higher metabolic rates and better water conservation. Spiders are ectotherms, so environmental temperatures affect their activity.

 

FEEDING, DIGESTION AND EXCRETION

Uniquely among chelicerates, the final sections of spiders' chelicerae are fangs, and the great majority of spiders can use them to inject venom into prey from venom glands in the roots of the chelicerae. The families Uloboridae and Holarchaeidae, and some Liphistiidae spiders, have lost their venom glands, and kill their prey with silk instead. Like most arachnids, including scorpions, spiders have a narrow gut that can only cope with liquid food and spiders have two sets of filters to keep solids out. They use one of two different systems of external digestion. Some pump digestive enzymes from the midgut into the prey and then suck the liquified tissues of the prey into the gut, eventually leaving behind the empty husk of the prey. Others grind the prey to pulp using the chelicerae and the bases of the pedipalps, while flooding it with enzymes; in these species, the chelicerae and the bases of the pedipalps form a preoral cavity that holds the food they are processing.

 

The stomach in the cephalothorax acts as a pump that sends the food deeper into the digestive system. The mid gut bears many digestive ceca, compartments with no other exit, that extract nutrients from the food; most are in the abdomen, which is dominated by the digestive system, but a few are found in the cephalothorax.

 

Most spiders convert nitrogenous waste products into uric acid, which can be excreted as a dry material. Malphigian tubules ("little tubes") extract these wastes from the blood in the hemocoel and dump them into the cloacal chamber, from which they are expelled through the anus.[8] Production of uric acid and its removal via Malphigian tubules are a water-conserving feature that has evolved independently in several arthropod lineages that can live far away from water, for example the tubules of insects and arachnids develop from completely different parts of the embryo. However, a few primitive spiders, the sub-order Mesothelae and infra-order Mygalomorphae, retain the ancestral arthropod nephridia ("little kidneys"), which use large amounts of water to excrete nitrogenous waste products as ammonia.

 

CENTRAL NERVOUS SYSTEM

The basic arthropod central nervous system consists of a pair of nerve cords running below the gut, with paired ganglia as local control centers in all segments; a brain formed by fusion of the ganglia for the head segments ahead of and behind the mouth, so that the esophagus is encircled by this conglomeration of ganglia. Except for the primitive Mesothelae, of which the Liphistiidae are the sole surviving family, spiders have the much more centralized nervous system that is typical of arachnids: all the ganglia of all segments behind the esophagus are fused, so that the cephalothorax is largely filled with nervous tissue and there are no ganglia in the abdomen in the Mesothelae, the ganglia of the abdomen and the rear part of the cephalothorax remain unfused.

 

Despite the relatively small central nervous system, some spiders (like Portia) exhibit complex behaviour, including the ability to use a trial-and-error approach.

 

SENSE ORGANS

EYES

Spiders have primarily four pairs of eyes on the top-front area of the cephalothorax, arranged in patterns that vary from one family to another. The principal pair at the front are of the type called pigment-cup ocelli ("little eyes"), which in most arthropods are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup. However, in spiders these eyes are capable of forming images. The other pairs, called secondary eyes, are thought to be derived from the compound eyes of the ancestral chelicerates, but no longer have the separate facets typical of compound eyes. Unlike the principal eyes, in many spiders these secondary eyes detect light reflected from a reflective tapetum lucidum, and wolf spiders can be spotted by torch light reflected from the tapeta. On the other hand, jumping spiders' secondary eyes have no tapeta.

 

Other differences between the principal and secondary eyes are that the latter have rhabdomeres that point away from incoming light, just like in vertebrates, while the arrangement is the opposite in the former. The principal eyes are also the only ones with eye muscles, allowing them to move the retina. Having no muscles, the secondary eyes are immobile.

 

Some jumping spiders' visual acuity exceeds by a factor of ten that of dragonflies, which have by far the best vision among insects; in fact the human eye is only about five times sharper than a jumping spider's. They achieve this by a telephoto-like series of lenses, a four-layer retina and the ability to swivel their eyes and integrate images from different stages in the scan. The downside is that the scanning and integrating processes are relatively slow.

 

There are spiders with a reduced number of eyes, of these those with six-eyes are the most numerous and are missing a pair of eyes on the anterior median line, others species have four-eyes and some just two. Cave dwelling species have no eyes, or possess vestigial eyes incapable of sight.

 

OTHER SENSES

As with other arthropods, spiders' cuticles would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly bristles called setae, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell, often by means of setae. Pedipalps carry a large number of such setae sensitive to contact chemicals and air-borne smells, such as female pheromones. Spiders also have in the joints of their limbs slit sensillae that detect forces and vibrations. In web-building spiders, all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively.

 

Like most arthropods, spiders lack balance and acceleration sensors and rely on their eyes to tell them which way is up. Arthropods' proprioceptors, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well understood. On the other hand, little is known about what other internal sensors spiders or other arthropods may have.

 

LOCOMOTION

Each of the eight legs of a spider consists of seven distinct parts. The part closest to and attaching the leg to the cephalothorax is the coxa; the next segment is the short trochanter that works as a hinge for the following long segment, the femur; next is the spider's knee, the patella, which acts as the hinge for the tibia; the metatarsus is next, and it connects the tibia to the tarsus (which may be thought of as a foot of sorts); the tarsus ends in a claw made up of either two or three points, depending on the family to which the spider belongs. Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, spiders and a few other groups still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors. The only extensor muscles in spider legs are located in the three hip joints (bordering the coxa and the trochanter). As a result, a spider with a punctured cephalothorax cannot extend its legs, and the legs of dead spiders curl up. Spiders can generate pressures up to eight times their resting level to extend their legs, and jumping spiders can jump up to 50 times their own length by suddenly increasing the blood pressure in the third or fourth pair of legs. Although larger spiders use hydraulics to straighten their legs, unlike smaller jumping spiders they depend on their flexor muscles to generate the propulsive force for their jumps.

 

Most spiders that hunt actively, rather than relying on webs, have dense tufts of fine hairs between the paired claws at the tips of their legs. These tufts, known as scopulae, consist of bristles whose ends are split into as many as 1,000 branches, and enable spiders with scopulae to walk up vertical glass and upside down on ceilings. It appears that scopulae get their grip from contact with extremely thin layers of water on surfaces. Spiders, like most other arachnids, keep at least four legs on the surface while walking or running.

 

SILK PRODUCTION

The abdomen has no appendages except those that have been modified to form one to four (usually three) pairs of short, movable spinnerets, which emit silk. Each spinneret has many spigots, each of which is connected to one silk gland. There are at least six types of silk gland, each producing a different type of silk.

 

Silk is mainly composed of a protein very similar to that used in insect silk. It is initially a liquid, and hardens not by exposure to air but as a result of being drawn out, which changes the internal structure of the protein. It is similar in tensile strength to nylon and biological materials such as chitin, collagen and cellulose, but is much more elastic. In other words, it can stretch much further before breaking or losing shape.

 

Some spiders have a cribellum, a modified spinneret with up to 40,000 spigots, each of which produces a single very fine fiber. The fibers are pulled out by the calamistrum, a comb-like set of bristles on the jointed tip of the cribellum, and combined into a composite woolly thread that is very effective in snagging the bristles of insects. The earliest spiders had cribella, which produced the first silk capable of capturing insects, before spiders developed silk coated with sticky droplets. However, most modern groups of spiders have lost the cribellum.

 

Tarantulas also have silk glands in their feet.

 

Even species that do not build webs to catch prey use silk in several ways: as wrappers for sperm and for fertilized eggs; as a "safety rope"; for nest-building; and as "parachutes" by the young of some species.

 

REPRODUCTION AND LIFE CYCLE

Spiders reproduce sexually and fertilization is internal but indirect, in other words the sperm is not inserted into the female's body by the male's genitals but by an intermediate stage. Unlike many land-living arthropods, male spiders do not produce ready-made spermatophores (packages of sperm), but spin small sperm webs on to which they ejaculate and then transfer the sperm to special syringe-like structures, palpal bulbs or palpal organs, borne on the tips of the pedipalps of mature males. When a male detects signs of a female nearby he checks whether she is of the same species and whether she is ready to mate; for example in species that produce webs or "safety ropes", the male can identify the species and sex of these objects by "smell".

 

Spiders generally use elaborate courtship rituals to prevent the large females from eating the small males before fertilization, except where the male is so much smaller that he is not worth eating. In web-weaving species, precise patterns of vibrations in the web are a major part of the rituals, while patterns of touches on the female's body are important in many spiders that hunt actively, and may "hypnotize" the female. Gestures and dances by the male are important for jumping spiders, which have excellent eyesight. If courtship is successful, the male injects his sperm from the palpal bulbs into the female's genital opening, known as the epigyne, on the underside of her abdomen. Female's reproductive tracts vary from simple tubes to systems that include seminal receptacles in which females store sperm and release it when they are ready.

 

Males of the genus Tidarren amputate one of their palps before maturation and enter adult life with one palp only. The palps are 20% of male's body mass in this species, and detaching one of the two improves mobility. In the Yemeni species Tidarren argo, the remaining palp is then torn off by the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime, the female feeds on the palpless male. In over 60% of cases, the female of the Australian redback spider kills and eats the male after it inserts its second palp into the female's genital opening; in fact, the males co-operate by trying to impale themselves on the females' fangs. Observation shows that most male redbacks never get an opportunity to mate, and the "lucky" ones increase the likely number of offspring by ensuring that the females are well-fed. However, males of most species survive a few matings, limited mainly by their short life spans. Some even live for a while in their mates' webs.

 

Females lay up to 3,000 eggs in one or more silk egg sacs, which maintain a fairly constant humidity level. In some species, the females die afterwards, but females of other species protect the sacs by attaching them to their webs, hiding them in nests, carrying them in the chelicerae or attaching them to the spinnerets and dragging them along.

 

Baby spiders pass all their larval stages inside the egg and hatch as spiderlings, very small and sexually immature but similar in shape to adults. Some spiders care for their young, for example a wolf spider's brood cling to rough bristles on the mother's back, and females of some species respond to the "begging" behaviour of their young by giving them their prey, provided it is no longer struggling, or even regurgitate food.

 

Like other arthropods, spiders have to molt to grow as their cuticle ("skin") cannot stretch. In some species males mate with newly molted females, which are too weak to be dangerous to the males. Most spiders live for only one to two years, although some tarantulas can live in captivity for over 20 years.

 

SIZE

Spiders occur in a large range of sizes. The smallest, Patu digua from Colombia, are less than 0.37 mm in body length. The largest and heaviest spiders occur among tarantulas, which can have body lengths up to 90 mm and leg spans up to 250 mm.

 

EVOLUTION

FOSSIL RECORD

Although the fossil record of spiders is considered poor, almost 1000 species have been described from fossils. Because spiders' bodies are quite soft, the vast majority of fossil spiders have been found preserved in amber. The oldest known amber that contains fossil arthropods dates from 130 million years ago in the Early Cretaceous period. In addition to preserving spiders' anatomy in very fine detail, pieces of amber show spiders mating, killing prey, producing silk and possibly caring for their young. In a few cases, amber has preserved spiders' egg sacs and webs, occasionally with prey attached; the oldest fossil web found so far is 100 million years old. Earlier spider fossils come from a few lagerstätten, places where conditions were exceptionally suited to preserving fairly soft tissues.

 

The oldest known exclusively terrestrial arachnid is the trigonotarbid Palaeotarbus jerami, from about 420 million years ago in the Silurian period, and had a triangular cephalothorax and segmented abdomen, as well as eight legs and a pair of pedipalps. Attercopus fimbriunguis, from 386 million years ago in the Devonian period, bears the earliest known silk-producing spigots, and was therefore hailed as a spider at the time of its discovery. However, these spigots may have been mounted on the underside of the abdomen rather than on spinnerets, which are modified appendages and whose mobility is important in the building of webs. Hence Attercopus and the similar Permian arachnid Permarachne may not have been true spiders, and probably used silk for lining nests or producing egg-cases rather than for building webs. The largest known fossil spider as of 2011 is the araneid Nephila jurassica, from about 165 million years ago, recorded from Daohuogo, Inner Mongolia in China. Its body length is almost 25 mm.

 

Several Carboniferous spiders were members of the Mesothelae, a primitive group now represented only by the Liphistiidae. The mesothelid Paleothele montceauensis, from the Late Carboniferous over 299 million years ago, had five spinnerets. Although the Permian period 299 to 251 million years ago saw rapid diversification of flying insects, there are very few fossil spiders from this period.

 

The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the Triassic well before 200 million years ago. Some Triassic mygalomorphs appear to be members of the family Hexathelidae, whose modern members include the notorious Sydney funnel-web spider, and their spinnerets appear adapted for building funnel-shaped webs to catch jumping insects. Araneomorphae account for the great majority of modern spiders, including those that weave the familiar orb-shaped webs. The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families.

 

WIKIPEDIA

Auction#181

 

Dimensions: 9" x 9" / 22.8cm x 22.8cm, hanging panel

 

Tesserae: Image transfer jigsaw ceramic tile, mixed media contents based upon photo selection

 

With extensive training in ceramic art and lead lighting in the 80’s, at Chisholm Institute in Melbourne, Kathryn majored in flat glass and acquired a love of strong colour placement and segmentation.

 

Kathryn spent three years working in two studios in Boston USA, designing and manufacturing stained glass and sandblasted art for commercial venues and custom designs for private residences.

 

Upon return home to Australia, she designed and built her own mudbrick house in the peaceful Central Victorian countryside, in Pipers Creek, a few kilometers from the township of Kyneton. It was the perfect environment in which to experiment with many different mosaicking techniques, which led to retail sales, public and private commissions, workshops, exhibitions and awards.

 

Best known for the Black Saturday Memorial in Kyneton, Kathryn has also created mosaic installations for the local sculpture park, schools, kindergarten and the nearby tourist venue – Kyneton Bushland Resort.

Open Studio bus tours are hosted weekly and to the general public annually, and work for sale is on display at two local galleries.

 

Kathryn Portelli ~ KP Mosaic Words

Website: www.kpmosaicwords.com

Central Victoria, Australia

 

MORE THAN YOU EVER WANTED TO KNOW ABOUT SPIDERS!

 

Spiders are chelicerates and therefore arthropods. As arthropods they have: segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo. Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the cephalothorax or prosoma, is a complete fusion of the segments that in an insect would form two separate tagmata, the head and thorax; the rear tagma is called the abdomen or opisthosoma.[6] In spiders, the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel. The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods. In fact, chelicerates' only appendages ahead of the mouth are a pair of chelicerae, and they lack anything that would function directly as "jaws". The first appendages behind the mouth are called pedipalps, and serve different functions within different groups of chelicerates.

 

Spiders and scorpions are members of one chelicerate group, the arachnids. Scorpions' chelicerae have three sections and are used in feeding. Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use. The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food. Scorpions' pedipalps generally form large claws for capturing prey, while those of spiders are fairly small appendages whose bases also act as an extension of the mouth; in addition, those of male spiders have enlarged last sections used for sperm transfer.

 

In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk. The upper surface of the cephalothorax is covered by a single, convex carapace, while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface

 

Like other arthropods, spiders are coelomates in which the coelom is reduced to small areas round the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows. The heart is a tube in the upper part of the body, with a few ostia that act as non-return valves allowing blood to enter the heart from the hemocoel but prevent it from leaving before it reaches the front end. However, in spiders, it occupies only the upper part of the abdomen, and blood is discharged into the hemocoel by one artery that opens at the rear end of the abdomen and by branching arteries that pass through the pedicle and open into several parts of the cephalothorax. Hence spiders have open circulatory systems. The blood of many spiders that have book lungs contains the respiratory pigment hemocyanin to make oxygen transport more efficient.

 

Spiders have developed several different respiratory anatomies, based on book lungs, a tracheal system, or both. Mygalomorph and Mesothelae spiders have two pairs of book lungs filled with haemolymph, where openings on the ventral surface of the abdomen allow air to enter and diffuse oxygen. This is also the case for some basal araneomorph spiders, like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs. The trachea system has most likely evolved in small ancestors to help resist desiccation. The trachea were originally connected to the surroundings through a pair of openings called spiracles, but in the majority of spiders this pair of spiracles has fused into a single one in the middle, and moved backwards close to the spinnerets.[8] Spiders that have tracheae generally have higher metabolic rates and better water conservation. Spiders are ectotherms, so environmental temperatures affect their activity.

 

Uniquely among chelicerates, the final sections of spiders' chelicerae are fangs, and the great majority of spiders can use them to inject venom into prey from venom glands in the roots of the chelicerae. The family Uloboridae has lost its venom glands, and kills its prey with silk instead. Like most arachnids, including scorpions, spiders have a narrow gut that can only cope with liquid food and spiders have two sets of filters to keep solids out. They use one of two different systems of external digestion. Some pump digestive enzymes from the midgut into the prey and then suck the liquified tissues of the prey into the gut, eventually leaving behind the empty husk of the prey. Others grind the prey to pulp using the chelicerae and the bases of the pedipalps, while flooding it with enzymes; in these species, the chelicerae and the bases of the pedipalps form a preoral cavity that holds the food they are processing.

 

The stomach in the cephalothorax acts as a pump that sends the food deeper into the digestive system. The mid gut bears many digestive ceca, compartments with no other exit, that extract nutrients from the food; most are in the abdomen, which is dominated by the digestive system, but a few are found in the cephalothorax.

 

Most spiders convert nitrogenous waste products into uric acid, which can be excreted as a dry material. Malphigian tubules ("little tubes") extract these wastes from the blood in the hemocoel and dump them into the cloacal chamber, from which they are expelled through the anus. Production of uric acid and its removal via Malphigian tubules are a water-conserving feature that has evolved independently in several arthropod lineages that can live far away from water,[14] for example the tubules of insects and arachnids develop from completely different parts of the embryo. However, a few primitive spiders, the sub-order Mesothelae and infra-order Mygalomorphae, retain the ancestral arthropod nephridia ("little kidneys"), which use large amounts of water to excrete nitrogenous waste products as ammonia

 

Most spiders have four pairs of eyes on the top-front area of the cephalothorax, arranged in patterns that vary from one family to another.[8] The pair at the front are of the type called pigment-cup ocelli ("little eyes"), which in most arthropods are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup. However, the main eyes at the front of spiders' heads are pigment-cup ocelli that are capable of forming images. The other eyes are thought to be derived from the compound eyes of the ancestral chelicerates, but no longer have the separate facets typical of compound eyes. Unlike the main eyes, in many spiders these secondary eyes detect light reflected from a reflective tapetum lucidum, and wolf spiders can be spotted by torch light reflected from the tapeta. On the other hand, jumping spiders' secondary eyes have no tapeta. Some jumping spiders' visual acuity exceeds by a factor of ten that of dragonflies, which have by far the best vision among insects; in fact the human eye is only about five times sharper than a jumping spider's. They achieve this by a telephoto-like series of lenses, a four-layer retina and the ability to swivel their eyes and integrate images from different stages in the scan. The downside is that the scanning and integrating processes are relatively slow.

 

There are spiders with a reduced number of eyes, of these those with six-eyes are the most numerous and are missing a pair of eyes on the anterior median line, others species have four-eyes and some just two. Cave dwelling species have no eyes, or possess vestigial eyes incapable of sight.

 

As with other arthropods, spiders' cuticles would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly bristles called setae, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell, often by means of setae. Pedipalps carry a large number of such setae sensitive to contact chemicals and air-borne smells, such as female pheromones. Spiders also have in the joints of their limbs slit sensillae that detect forces and vibrations. In web-building spiders, all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively.

 

Like most arthropods, spiders lack balance and acceleration sensors and rely on their eyes to tell them which way is up. Arthropods' proprioceptors, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well understood. On the other hand, little is known about what other internal sensors spiders or other arthropods may have.

 

Each of the eight legs of a spider consists of seven distinct parts. The part closest to and attaching the leg to the cephalothorax is the coxa; the next segment is the short trochanter that works as a hinge for the following long segment, the femur; next is the spider's knee, the patella, which acts as the hinge for the tibia; the metatarsus is next, and it connects the tibia to the tarsus (which may be thought of as a foot of sorts); the tarsus ends in a claw made up of either two or three points, depending on the family to which the spider belongs. Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, spiders and a few other groups still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors. The only extensor muscles in spider legs are located in the three hip joints (bordering the coxa and the trochanter). As a result, a spider with a punctured cephalothorax cannot extend its legs, and the legs of dead spiders curl up. Spiders can generate pressures up to eight times their resting level to extend their legs, and jumping spiders can jump up to 50 times their own length by suddenly increasing the blood pressure in the third or fourth pair of legs. Although larger spiders use hydraulics to straighten their legs, unlike smaller jumping spiders they depend on their flexor muscles to generate the propulsive force for their jumps.

 

Most spiders that hunt actively, rather than relying on webs, have dense tufts of fine hairs between the paired claws at the tips of their legs. These tufts, known as scopulae, consist of bristles whose ends are split into as many as 1,000 branches, and enable spiders with scopulae to walk up vertical glass and upside down on ceilings. It appears that scopulae get their grip from contact with extremely thin layers of water on surfaces. Spiders, like most other arachnids, keep at least four legs on the surface while walking or running.

 

The abdomen has no appendages except those that have been modified to form one to four (usually three) pairs of short, movable spinnerets, which emit silk. Each spinneret has many spigots, each of which is connected to one silk gland. There are at least six types of silk gland, each producing a different type of silk.

 

Silk is mainly composed of a protein very similar to that used in insect silk. It is initially a liquid, and hardens not by exposure to air but as a result of being drawn out, which changes the internal structure of the protein. It is similar in tensile strength to nylon and biological materials such as chitin, collagen and cellulose, but is much more elastic. In other words, it can stretch much further before breaking or losing shape.

 

Some spiders have a cribellum, a modified spinneret with up to 40,000 spigots, each of which produces a single very fine fiber. The fibers are pulled out by the calamistrum, a comb-like set of bristles on the jointed tip of the cribellum, and combined into a composite woolly thread that is very effective in snagging the bristles of insects. The earliest spiders had cribella, which produced the first silk capable of capturing insects, before spiders developed silk coated with sticky droplets. However, most modern groups of spiders have lost the cribellum.

 

Tarantulas also have silk glands in their feet.

 

Even species that do not build webs to catch prey use silk in several ways: as wrappers for sperm and for fertilized eggs; as a "safety rope"; for nest-building; and as "parachutes" by the young of some species

 

Spiders reproduce sexually and fertilization is internal but indirect, in other words the sperm is not inserted into the female's body by the male's genitals but by an intermediate stage. Unlike many land-living arthropods, male spiders do not produce ready-made spermatophores (packages of sperm), but spin small sperm webs on to which they ejaculate and then transfer the sperm to special syringe-like structures, palpal bulbs or palpal organs, borne on the tips of the pedipalps of mature males. When a male detects signs of a female nearby he checks whether she is of the same species and whether she is ready to mate; for example in species that produce webs or "safety ropes", the male can identify the species and sex of these objects by "smell".

 

Spiders generally use elaborate courtship rituals to prevent the large females from eating the small males before fertilization, except where the male is so much smaller that he is not worth eating. In web-weaving species, precise patterns of vibrations in the web are a major part of the rituals, while patterns of touches on the female's body are important in many spiders that hunt actively, and may "hypnotize" the female. Gestures and dances by the male are important for jumping spiders, which have excellent eyesight. If courtship is successful, the male injects his sperm from the palpal bulbs into the female's genital opening, known as the epigyne, on the underside of her abdomen. Female's reproductive tracts vary from simple tubes to systems that include seminal receptacles in which females store sperm and release it when they are ready.

 

Males of the genus Tidarren amputate one of their palps before maturation and enter adult life with one palp only. The palps are 20% of male's body mass in this species, and detaching one of the two improves mobility. In the Yemeni species Tidarren argo, the remaining palp is then torn off by the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime, the female feeds on the palpless male. In over 60% of cases, the female of the Australian redback spider kills and eats the male after it inserts its second palp into the female's genital opening; in fact, the males co-operate by trying to impale themselves on the females' fangs. Observation shows that most male redbacks never get an opportunity to mate, and the "lucky" ones increase the likely number of offspring by ensuring that the females are well-fed. However, males of most species survive a few matings, limited mainly by their short life spans. Some even live for a while in their mates' webs

 

Thanks, Wikipedia

Processed in GIMP as mounted painting.

Textures from CGtextures.com

Painterly effect via GMIC Segmentation and GMIC Dodge Sketch