Not Like a Hoover. Common Greenbottle Fly, Lucilia caesar, on Smyrnium perfoliatum, Perfoliate Alexanders, Hortus Botanicus, Amsterdam, The Netherlands
That 'tongue' - see inset - does look a bit like a Hoover, but it functions quite differently. Flies such as this Greenbottle don't chew or bite their food. Instead their mouthparts 'sponge', that is to say that they function by capillary action.
The labellum - the part of the 'tongue' that looks like the sucking end of our Hoover - has many grooves (visible only under a microscope) called pseudotracheae. If the food on its sweeping area is not sufficiently liquid they can emit a kind of saliva. The liquid mixture - in the case of these Alexanders flowers: nectar - moves upwards into Lucilia's narrow labium not by its own sucking action but through intermolecular forces in play between the liquid and the inner wall of the labial tube; so a bit like a sponge.
Not Like a Hoover. Common Greenbottle Fly, Lucilia caesar, on Smyrnium perfoliatum, Perfoliate Alexanders, Hortus Botanicus, Amsterdam, The Netherlands
That 'tongue' - see inset - does look a bit like a Hoover, but it functions quite differently. Flies such as this Greenbottle don't chew or bite their food. Instead their mouthparts 'sponge', that is to say that they function by capillary action.
The labellum - the part of the 'tongue' that looks like the sucking end of our Hoover - has many grooves (visible only under a microscope) called pseudotracheae. If the food on its sweeping area is not sufficiently liquid they can emit a kind of saliva. The liquid mixture - in the case of these Alexanders flowers: nectar - moves upwards into Lucilia's narrow labium not by its own sucking action but through intermolecular forces in play between the liquid and the inner wall of the labial tube; so a bit like a sponge.