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 Muscci domestica. In the 
family Tachinidse, 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 Dexidse, of similar habits, there are also many 
which closely resemble the house fly. In the family 
Sarcophagidse, 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 Anthomyidse, 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 bv looking at them with the naked eye. 
The habits of the different genera of Muscidae are 
