ABSTRACT
The fungal pathogen Entomophthora muscae (Cohn) Fresenius is known to infect a number of species of filth-dwelling Diptera, though we have few data to quantify levels of activity in these hosts. Literature is reviewed regarding the life cycle and taxonomic status of E. muscae s.l. Seasonal activity in Musca domestica L. on a southern California dairy was essentially the same as that previously reported for poultry operations in the region, with fall epizootics that reached infection levels of 60-80%. Stomoxys calcitrans L. adults were not infected by the pathogen in the field, in spite of being collected in an area and time of high pathogen activity in M. domestica. A laboratory study was done to assess the impact of E. muscae on fecundity in M. domestica. Flies which were exposed to the pathogen at <36 h of age did not oviposit before they died. Flies exposed at 48-96 h of age laid only 20% as many eggs as uninfected females from the same cohort over their lifespan, in spite of developing and holding mature eggs. Thus E. muscae appears to modify host behavior in M. domestica, as previously noted in Delia and Psila. Some areas of needed research are noted.
