HOUSE FLIES. 5 
of the flies in dining rooms in different parts of the country, and 
out of a total of 23,087 flies 22,808 were I/usca domestica—that is, 
98.8 per cent of the whole number captured. The remainder, consist- 
ing of 1.2 per cent of the whole, comprised various species, including 
those mentioned above. 
LIFE HISTORY OF THE TRUE HOUSE FLY. 
Musca domestica commonly lays its eggs (figs. 9, 10) upon horse 
manure. This substance seems to be its favorite larval food. It will 
also breed in human excrement, and from this habit it becomes very 
lic, 8.—The dung fly (Sepsis violacea) : Adult, puparium, and details. All 
enlarged. (Author’s illustration.) 
dangerous to the health of human beings, carrying as it does the 
germs of intestinal diseases, such as typhoid fever and cholera, from 
the excreta to food supplies. It has also been found to breed freely 
in hog manure and to some extent in cow and chicken manure. In- 
deed, it will lay its eggs on a great variety of decaying vegetable 
and animal material, but of the flies that infest dwelling houses, 
both in cities and on farms, a vast proportion come from horse 
manure. 
It often happens, however, that this fly is very abundant in locali- 
ties where there is little or no horse manure, and in such cases it 
will be found breeding in other manure or in slops or fermenting 
vegetable material, such as spent hops, bran, ensilage, or rotting 
potatoes. Accumulations of organic material on the dumping 
grounds of towns and cities often produce flies in great numbers. 
