DISEASES OF FLIES 23 I 



one finds between each of the segments of a diseased and 

 consequently deceased fly. A conidium now develops by the 

 constriction of the apical region of the conidiophore. When it 

 is ripe the conidium is usually bell-shaped, measuring 25 — 30//, 

 in length ; it generally contains a single oil globule. In a 

 remarkable manner it is now shot off from the conidiophore, 

 often for a distance of about a centimetre, and in this way the 

 ring or halo of white spores, which is seen around the dead fly, 

 is formed" (Hewitt, 1910). In many cases the fly is attached 

 to the surface by its extended proboscis. 



E. muscce has been found on several species of Syrphidce, and 

 Thaxter (1888) records its occurrence in L. ccesar and C. vonii- 

 toria. The writer has on several occasions attempted to infect 

 C. erytJirocephala, S. carnaria, and L. ccesar, by confining them 

 in cages together with infected flies but without success, and he 

 does not remember to have seen naturally infected specimens. 

 Thaxter (1888) states that two other species o^ Qvc\\)us3i, E. sphcBro- 

 sperma and E. americana, occasionally attack house-flies and 

 blow-flies. The former species destroys insects belonging to 

 several orders. 



Persistence of the fungus from season to season. 



Some workers assert that they have observed resting spores, 

 but the question of their production is still uncertain and needs 

 further investigation. Without them it is extremely difficult to 

 understand how the gap in the history of the empusa, between 

 the late autumn of one year and the summer of the next, is filled 

 up. It has been suggested, however, that the species may be 

 kept alive in the few flies, which develop during the winter in 

 stables, bake-houses, etc. 



A rtificial cultivation. 



" If nature could be assisted in her methods, and the fungus 

 brought into contact with the flies, or their larvae, by scientific 

 methods, it seems probable that the number of flies might 

 thereby be brought under proper control. To this purpose a 



