230 DISEASES OF FLIES 



" Empusa uiuscce belongs to the group Entomophthorece, the 

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

 cases are productive of great mortality among the individuals of 

 the species attacked. In this country it may be found from 

 about the beginning of July to the end of October, and usually 

 occurs indoors. It appears to be ver}^ uncommon out of doors " 

 (Hewitt, 1910, p. 372). 



Mode of hifixtion. 



The mode of infection is at present not well understood. 

 Confinement of healthy flies with those which have died of the 

 disease does not necessarily result in infection. The writer has 

 occasionally been greatly hampered in experiments on the trans- 

 mission of bacteria by empusa disease in the fly cages. In 

 certain instances all the flies died of empusa infection within a 

 few days. He has, however, been unable to infect from flies 

 which had been dead of empusa for a few weeks either by 

 confining living flies with dead infected flies, or by feeding with 

 sugar syrup contaminated with the remains of dead flies, or by 

 painting living flies with infected syrup. Brefeld (1873) suc- 

 cessfully inoculated the spores under the skin and obtained 

 germination of the gonidia on the surface of the fly. Olive's 

 (1906) experiments with an allied species E. sciara indicate 

 that infection may occur in the very young larvae on the surface 

 of the excreta, before they burrow into its depths. 



It has generally been supposed that the empusa spore lodges 

 on the surface of the insect and adheres, and that a small 

 germinating hypha develops, pierces the chitin and eventually 

 penetrates the fat-body. Here gemmae are formed which pene- 

 trate to all parts of the body. After a few days the fly's body 

 is completely penetrated by the fungus which destroys all the 

 internal organs and tissues. " The whole body is filled with 

 gemmae, which germinate and produce ramifying hyphae. The 

 latter pierce the softer portions of the body wall between the 

 segments and produce short, stout, conidiophores, which are 

 closely packed together in a palisade-like mass to form a compact 

 cushion of conidiophores, which is the transverse white ring that 



