I found about a dozen dead flies like this one, head down, tongues extended, clinging to the flower heads of meadow foxtail grass. They’ve been killed by a fungus called Entomophthora muscae, that invades the insect through one of the joints in its external skeleton and attacks its nervous system, modifying its behaviour so that it climbs to the top of grass stems and clings on while the fungus digests its internal organs. Fully fed, the fungus then erupts through the joints in its victim's body, covering the dead fly's abdomen with a felty mass of fungal material that produces gelatinous-coated spores that cling to the next hapless fly that arrives in the scene, sealing its fate. The spores can be fired some distance from the corpse, so they also coat surrounding vegetation. The bottom photograph shows the highly magnified (x200) sticky spores and the next one up shows a mass of sticky spores adhering to a hair on the leg of the corpse (x100). It's Hammer House of Horrors stuff.