scraping off the albuminous polish, and leaving
tracings of its depredations in the soiled and spotted appearance which
it occasions on them. It is by means of these also that it teases us in
the heat of summer, when it alights on the hand or face to sip the
perspiration as it exudes from, and is condensed upon, the skin."

[Illustration: 85. Larva; _a_, Pupa-case of House fly.]

[Illustration: 86. Larva of Flesh fly.]

Every one notices that house flies are most abundant around barns in
August and September, and it is in the ordure of stables that the early
stages of this insect are passed. No one has traced the transformations
of this fly in our country, but we copy from Bouche's work on the
transformations of insects, the rather rude figures of the larva (Fig.
85), and pupa-case (_a_) of the Musca domestica of Europe, which is
supposed to be our species. Bouche states that the larva is cylindrical,
rounded posteriorly, smooth and shining, fleshy, and yellowish white,
and four lines long. The pupa-case, or puparium, is dark reddish-brown,
and three lines in length. It remains in the pupa state from eight to
fourteen days. In Europe it is preyed upon by minute ichneumon flies
(Chalcids). The flesh fly, Musca Caesar, or the Blue-bottle fly, feeds
upon decaying animal matter. Its larva (Fig. 86) is long, cylindrical,
the head being pointed, and the body conical, the posterior end being
squarely docked. The larva of a Sargus-like form which feeds on offal,
transforms into a flattened pupa-case (Fig. 87), provided with long,
scattered hairs. The House fly disappears in autumn, at the approach of
cold weather, though a few individuals pass through the winter,
hibernating in houses, and when the rooms are heated may often be seen
flying on the windows. Other species fly early in March, on warm days,
having hibernated under leaves, and the bark of trees, moss, etc. An
allied species, the M. vomitoria, is the Meat fly. Closely allied are
the parasitic species of Tachina, which live within the bodies of
caterpillars and other insects, and are among the most beneficial of
insects, as they prey on thousands of injurious caterpillars. Another
fly of this Muscid group, the Idia Bigoti, according to Coquerel and
Mondiere, produces in the natives of Senegal, hard, red, fluctuating
tumors, in which the larva resides.

[Illustration: 87. Larva of a Sargus-like fly.]

Many of the smaller Muscids mine leaves, running galleries withi