overripe fruit.

All of these species, however, are greatly dwarfed in numbers by the
common house fly. In 1900 the senior author made collections of the
flies in dining rooms in different parts of the country, and found that
the true house fly made up 98.8 per cent of the whole number captured.
The remainder comprised various species, including those mentioned
above.

[Footnote 8: _Drosophila ampelophila_ Loew.]

[Illustration: Fig. 3.--The true house fly. Enlarged.]




WHERE THE TRUE HOUSE FLY LAYS ITS EGGS.


The true house fly (fig. 3), which is found in nearly all parts of the
world, is a medium-sized fly with four black stripes on the back and a
sharp elbow in one of the veins of the wings. The house fly can not
bite, its mouth parts being spread out at the tip for sucking up liquid
substances.

The eggs (figs. 4, 5) are laid upon horse manure. This substance seems
to be its favorite larval food. It will breed also in human excrement,
and because of this habit it is very 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