Donegal Wildlife Database - Fungi - Entomophthora
Entomophthora muscae complex is a fungus that attacks flies and eventually kills them. The fungus enters the digestive tract and expands until it can be seen forcing itself between the abdominal plates. Before the fly dies, it crawls to a high point on a plant, straightens its hind legs and opens its wings. The resultant site and posture of the fly ensures that the fungal spores have the best possible chance of distribution.
This behaviour is known as 'Summit disease'.
The two species I have seen infected are:-
Scathophaga stercoraria - a dung fly
And Melanostoma scalare - a hoverfly.
Eventually, once the spores have dispersed, the victim is left hanging as a skeletal husk.
I am astonished that a fungus can control an insect to such an extent that it forces it to move upwards, adopt a particular posture and open its wings. Most impressive.