Giant ichneumon megarhyssa-Aug_2017_DSC_2237
The female Giant Ichneumon wasp, Megarhyssa marcurus is equipped with an ovipositor several times her own length. She uses this to which she drills into the side of diseased trees in order to lay an egg on the larva of another insect, the pigeon horntail (Tremex), which is a sawfly, a close relative of wasps, bees and ants. The horntail larva grows, and is fed upon by the ichneumon larva. The ovipositor is composed of a central delivery shaft which drills into the wood and through which the egg passes. There are another two outer sheaths that protect and stiffen the central “hypodermic needle”, these can be seen arcing away from the tip of the wasp’s tail. Before the drilling begins the wasp walks methodically up and down the tree, “feeling” with her antenna to sense the presence of the host horntail larva buried below the surface. Once a host larva has been detected she raises her tail and brings the ovipositor into position. At the beginning and end of the drilling process the last segments of the tail hinge open and a flexible membrane is inflated between them, (this is the white moon-shaped structure in the photo). This is used to manipulate the ovipositer as it enters and leaves the wood. The photo here is at the end of the laying process, the wasp is using her abdominal disc to withdraw the ovipositor from the wood.
Giant ichneumon megarhyssa-Aug_2017_DSC_2237
The female Giant Ichneumon wasp, Megarhyssa marcurus is equipped with an ovipositor several times her own length. She uses this to which she drills into the side of diseased trees in order to lay an egg on the larva of another insect, the pigeon horntail (Tremex), which is a sawfly, a close relative of wasps, bees and ants. The horntail larva grows, and is fed upon by the ichneumon larva. The ovipositor is composed of a central delivery shaft which drills into the wood and through which the egg passes. There are another two outer sheaths that protect and stiffen the central “hypodermic needle”, these can be seen arcing away from the tip of the wasp’s tail. Before the drilling begins the wasp walks methodically up and down the tree, “feeling” with her antenna to sense the presence of the host horntail larva buried below the surface. Once a host larva has been detected she raises her tail and brings the ovipositor into position. At the beginning and end of the drilling process the last segments of the tail hinge open and a flexible membrane is inflated between them, (this is the white moon-shaped structure in the photo). This is used to manipulate the ovipositer as it enters and leaves the wood. The photo here is at the end of the laying process, the wasp is using her abdominal disc to withdraw the ovipositor from the wood.