Fly Death Fungi

Behavior

Soon after a fly dies from infection with this pathogenic fungus, large primary conidia are produced at the apex of a conidiophore which emerge from the intersegmental membranes. When the spores are mature they are forcibly ejected and may fall onto flies resting nearby. If no hosts are available for infection, a smaller secondary conidium may develop. The conidia germinate within a few hours and a germ tube begins to penetrate the insect's cuticle. Once this reaches the haemocoel, the protoplast flows through the tube and into the fly's haemolymph. The mycelium of the fungus may grow into an area of the brain that controls the behaviour of the fly, forcing it to land on a surface and crawl upwards. The hyphae gradually grow through the whole of the body, digesting the guts, and the fly dies in about five to seven days. When it is critically ill, it tends to crawl to a high point, straighten its hind legs and open its wings, a behaviour that ensures that the fungal spores are dispersed as widely as possible. Some three hours later, conidiophores start to develop and a new shower of conidia is initiated.

Habitat

Outbreaks of infection with "Entomophthora muscae" tend to occur in the spring and autumn. The fungus is found in most temperate regions and sporulation usually takes place in cool, humid conditions in areas where flies congregate and rest. In houses, the corpses of flies are frequently seen attached to windows or window frames, a place where other flies may easily become infected. In the open, they may be seen attached to the underneath of leaves, on fences and walls, in agricultural buildings and poultry houses.