Fungal infection of flies occurs primarily through the cuticle rather than through the digestive tract.
The fungi penetrate the cuticle and proliferate in the haemolymph. The fly then dies quite rapidly.
The fungus emerges through the cuticle, forming a mycelium which contains the next generation of spores.
These spores are then spread to other flies by wind, or by direct contact between dead and living flies.
It takes five to seven days for a flie to die after its cuticle has been penetrated by fungus.
To be active, the spores need humid conditions. Therefore, even though many fungi are able to kill flies, the natural fungal population level is rarely high enough to have a significant impact on fly populations.
Fungi form stages resistant to dry conditions, in order to survive throughout the year. As a consequence, there is a continuous level of resting spores in the environment.
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