CHAPTER XI 



THE FUNGAL DISEASE : EMPU^A MUSCAE COHN 



Probably the most important of all the enemies of the house- 

 fly is the parasitic fungus Empusa muscae. Towards the end of the 

 summer large numbers of flies may be found attached in a rigid 

 condition to the ceiling, walls or window-panes. They have an 

 extremely life-like appearance, and it is not until one examines 

 them closely or has touched them that their inanimate, so far as 

 the life of the fly is concerned, condition is discovered. These 

 flies have been killed by the fungus Empusa muscae Cohn, and in 

 the later stages of the disease its fungal nature is recognised by 

 the fact that a white ring of fungal spores may be seen around the 

 fly on the substratum to which it is attached (fig. 72). The 

 abdomen of the fly is swollen considerably, and white masses of 

 sporogenous fungal hyphae may be seen projecting for a short 

 distance from the body of the fly, between the segments, giving 

 the abdomen a transversely striped black and white appearance. 



The majority of flies which die in the late autumn — and it is 

 then that most of the flies which have been present during the 

 summer months perish — are killed by this fungus. Its occurrence, 

 therefore, is of no little economic value, especially if it were possible 

 to artificially cultivate it and destroy the flies in the early summer 

 instead of being compelled to wait until the autumn for the 

 natural course of events. 



Empusa muscae belongs to the group Entomophthoreae, the 

 members of which confine their attacks to insects, and in many 

 cases, as in the case of the present species, are productive of great 

 mortality among the individuals of the species of insect attacked. 

 In England it may be found from the beginning of July to the 



