(125) 



366 C. GOEDON HEWITT. 



V. NATURAL ENEMIES AND OCCASIONAL PARASITES. 



The most important of all the natural enemies of M. 

 domesticais the parasitic fungus Empusa muscaa, which 

 will be described here ; this is the most potent of the natural 

 means of destruction. Of animals, apart from the higher 

 animals such as birds, spiders probably account for the 

 greatest number, though owing to the normally clean con- 

 dition of the modern house these enemies of the house-fly are 

 refused admittance. I have been unable to rear any insect 

 parasites, such as ichneumons, from M. domestic a. Their 

 life indoors and the cryptic habits of the larvae no doubt save 

 them from the attacks of such insects; but Packard (1874) 

 records the occurrence of the pupa of what was probably a 

 Dermestid beetle, which he figures; this was found in a pupa 

 of M. domestica. Predatory beetles and their larvae pro- 

 bably destroy the larvae, and Berg (1898) states that a species 

 of beetle, Trox suberosus F., known as " Champi " in 

 S. America, is an indirect destructor of the common fly. I 

 have frequently observed the common wasp, Vespa ger- 

 manica, seize M. domestica and carry it away. In some 

 places in India it is the custom, so I have been told by resi- 

 dents, to employ a species of Mantis, one of the predatory 

 " praying insects," to destroy the house-flies. 



In view of the fact that the Arachnids Chernes iiodosus 

 and the species of Gamasid are occasionally found actually 

 attached in a firm manner to M. domestica, they will be 

 described under this head, but it must be clearly understood 

 that it is still an open question whether they are external 

 parasites in the true sense of the word, or whether M. domes- 

 tica, instead of being the host, is merely the transporting 

 agent as it appears to be in the majority of cases. For the 

 present they may be termed for convenience " occasional 

 parasites," in view of the fact that they have been found 

 occasionally feeding upon M. domestica. 



