llenia rudis_ Fab.]
[Footnote 4: _Calliphora erythrocephala_ Meig.]
[Footnote 5: _Phormia regina_ Meig. and _P. terrae-novae_ Desv.]
[Footnote 6: _Lucilia caesar_ L., _L. sericata_ Meig., and other species
of the genus.]

There is still another species, smaller than any of those so far
mentioned, which is sometimes called the "lesser house fly."[7] This
insect is distinguished from the ordinary house fly by its paler and
more pointed body. The male, which is commoner than the female, has
large pale patches at the base of the abdomen, which are translucent
when the fly is seen on the window pane. These little flies are not the
young of the larger flies. Flies do not grow after the wings have once
expanded and dried.

[Footnote 7: _Fannia canicularis_ L.]

[Illustration: FIG. 1.--The stable fly. Much enlarged.]

[Illustration: FIG. 2.--One of the green-bottle flies (_Lucilia
caesar_). Much enlarged.]

In late summer and autumn many specimens of a small fruit fly, known as
the "vinegar fly,"[8] make their appearance, attracted by the odor of
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
also been found to breed freely in hog manure, in considerable numbers
in chicken dung, and to some extent in cow manure. Indeed, it will lay
its eggs on a great variety of decaying vegetable and animal materials,
but of th