2 THE HOUSE FLY— DISEASE CARRIER 



statement made by Doctor Sharp, is that the flies found 

 under such conditions are not house flies, but some 

 species closely resembling Musca domestica. In the 

 family Tachinidae, a group composed almost entirely 

 of species which lay their eggs upon other living in- 

 sects, there are many species which almost precisely 

 resemble the gray-and-black-striped house fly. In the 

 family Dexidae, of similar habits, there are also many 

 which closely resemble the house fly. In the family 

 Sarcophagidae, which includes most of the so-called 

 flesh flies, the species of which either live in carrion 

 or excreta or in dead insects or in putrid matter, and 

 are occasionally parasitic, as with the species which 

 breed in the egg-masses of grasshoppers, there are also 

 many species hardly to be distinguished from Musca. 

 There is another great family, the Anthomyidae, which 

 has many species which closely resemble the house 

 fly and give rise to many mistakes In identity. These 

 insects in their early stages feed upon decaying vege- 

 table matter and also to some extent upon growing 

 plants, and a few prey upon the eggs of grasshoppers. 

 Then, too, in the family Muscidae itself there are many 

 genera of similar habits and similar appearance. The 

 writer once, as a test, selected twenty distinct species 

 from among these insects and carefully pinned them 

 into a tray, asking chance visitors for several weeks 

 to pick out the true house flies from among them. No 

 one was ever able to distinguish between the different 

 forms by looking at them with the naked eye. 

 The habits of the different genera of Muscidae are 



