Thursday, June 16, 2016
A Day in the Life of a Dung Fly
Thursday's Guardian Country Diary is about dung flies Scathophaga stercoraria
These common insects carry out their courtship on dung but are particularly fond of cow-pats. This is a male, awaiting the arrival of females. They prefer fresh dung, before it becomes too crusty, for attracting the females that scent the trysting place from downwind.
Males usually outnumber them so there is intense competition for a mate, which females usually choosing the largest suitors. Their sex lives have been intensively studied because these insects are easy to rear under laboratory conditions - you can read about the intimate details of their mating habits by clicking here.
Their Latin generic name Scathophaga (originally Scatophaga, but it seems to have acquired an additional h) means 'dung-eater' but it is only the larvae, which hatch from eggs laid in animal dung, that do this. The adult flies are formidable hunters, needing to catch and eat other insects to complete their sexual development before they are capable of breeding. This one has caught a small hoverfly and is holding it between its front legs, in much the same way that mantids hold their prey.
Many dung flies suffer a gruesome fate when they are infected with a fungus called Entomophthora. Its hyphae grow into their host through its spiracles and invade its body, digesting it until it weakens. In the final phase the fungus turns its host into a zombie, affecting its nervous system in a way that makes it climb towards the light. The flies die clasping grass stems, where the spores erupt through their body and are passed on to other inquisitive flies that investigate the corpse.
The pictures below, taken using a microscope, show the sticky spores on the dead dung fly host.