Monday, July 22, 2013
I found numerous examples of mummified, dead flies of various species (but mostly dung flies) attached to plant stems in the garden during the early days of July, although the incidence of diseased flies has declined during the current hot weather. They've been killed by the fungus Entomophthora muscae.
The fungus invades the fly's body and slowly weakens it. In the final stages of infection the disease modifies the host's behaviour so that it crawls to an exposed position at the top of a plant stem and then dies. Soon fungal spores erupt from the insect's body, as you can see in the photo above, and the corpse is perfectly positioned to pass on the infection to other flies in the vicinity.
There have been numerous attempts to culture this fungus so that it could be used as a commercial biological insecticide for reducing house fly populations - with limited success.