8) 



STRUCTURE, DEVELOPMENT, AND BIONOMICS OF HOUSE-FLY. 371 



apparently by their stomal regions. These specimens may be 

 truly parasitic, as I am inclined to believe, since many Acari 

 are parasitic in the immature state, although the adults may 

 not be so ; on the other hand this form of attachment may be 

 employed as a means of maintaining a more secure hold of 

 the transporting insect. 



3. Fungal Disease Empusa muscse Cohn. 



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 con- 

 cerned, condition is discovered. These flies have been killed by 

 the fungus Empusa muse 33 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. The abdomen of the fly 

 is swollen considerably, and white masses of sporogenous 

 fungal hyphge 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 muscse 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 produc- 

 tive of great mortality among the individuals of the species of 



cult to identify immature Gamasids owing to the scarcity of knowledge 

 as to their life-histories, but he says that they are very like Diny c hell a 

 asperata Berl. 



