HOUSE FLIES. 7 
young of the larger flies, which, of course, is distinctly not the case. 
They breed in decaying vegetable material, in the excreta of animals, 
and in dead insects. 
Still another fly, and this one is still smaller, is a jet-black species 
known as the window fly (Scenopinus fenestralis L.), which in fact has 
become more abundant of later years. Its larva is a white, very 
slender, almost thread-like creature, and is found in cracks of the 
floor in buildings, where it feeds on other small insects. 
In the autumn, when fruit appears on the sideboard, many speci- 
mens of a small fruit-fly (Drosophila ampelophila Loew) (fig. 7) make 
their appearance, attracted by the odor of overripe fruit. 
A small, slender fly is not infrequently seen in houses, especially 
upon window panes. This is Sepsis violacea Meig., shown enlarged 
in figure 8. 
All of these species, however, are greatly dwarfed in numbers by 
Fig. 3.—A stable fly ( Muscina stabulans): Adult, larva, and details. Allenlarged. (Author’s illustration.) 
the common house fly. In 1900 the writer made collections of the 
flies in dining rooms in different parts of the country, and out of a 
total of 23,087 flies 22,808 were Musca domestica—that is, 98.8 per 
cent of the whole number captured. The remainder, consisting 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 upon horse manure. 
This substance seems to be its favorite larval food. It will oviposit 
on cow manure, but we have not been able to rear it in this substance. 
It will also breed in human excrement, and from this habit it becomes 
very dangerous to the health of human beings, carrying, as it does, 
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