Fig. 2.—The stable fly or biting house fly (Stomoxys calcitrans): Adult, larva, puparium, and details. All enlarged. (Author’s illustration.)
Several species of metallic greenish or bluish flies are also occasionally found in houses, the most abundant of which is the so-called blue-bottle fly (Calliphora erythrocephala Meig.). This insect is also called the blow-fly or meat-fly and breeds in decaying animal material. A smaller species, which may be called the small blue-bottle fly, is Phormia terrænovæ Desv. ([fig. 4]); and a third, which is green or blue in color and a trifle smaller than the large blue-bottle, is Lucilia cæsar L. ([fig. 5]).
There is still another species, smaller than any of those so far mentioned, which is known to entomologists as Homalomyia canicularis L., sometimes called the small house fly. A related species, H. brevis Rond., is shown in [figure 6]. H. canicularis is distinguished from the ordinary house fly by its paler and more pointed body and conical shape. The male, which is much commoner than 'the female, has large pale patches at the base of the abdomen, which are translucent when the fly is seen on a window pane. It is this species that is largely responsible for the prevalent idea that flies grow after gaining wings. Most people think that these little Homalomyias are the 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 specimens 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].
Fig. 3.—A stable fly (Muscina stabulans): Adult, larva, and details. All enlarged. (Author’s Illustration.)