These flies have likely succumb to the pathogenic fungus Entomopthora muscae, latin for “fly destoyer”. A spore landing on the exoskeleton will send mycelium into the fly’s body and feed on the internal organs for some days. Just before the flies die they are compelled to climb to the top of some vegetation, hold on tightly, spread their wings one last time and die. Up in the wind with wings lifted out of the way, the fungus emerges, releases new spores and the cycle continues. (An interesting video from KQED – https://www.kqed.org/science/1949314/this-killer-fungus-turns-flies-into-zombies)
