Flesh-flies

(Family Sarcophagidae.)

This is a large group of flies, comprising very many species, and as the scientific name indicates they are called "flesh-flies" because many of them live in the larval state in the bodies of dead animals. Although, as just stated, many of the so-called flesh-flies are flesh feeders, the group as a whole is a variable one in habit. The larvae of some live in decaying vegetable matter and fruits, others live in dung and others are practically parasitic upon living insects. One genus (Sarcophila) is a parasite of mammalia and even of human beings, depositing its young in the nostrils where they cause great suffering and even death. Several species of this family are referred to in the medical literature of "myiasis" which means the parasitism of human beings by flies.

The females of the flesh-flies may deposit eggs in large numbers or they may deposit living larvae, as just indicated, the eggs being hatched before they have left the body of the female. A number of famous insects belong to this group. The insect popularly known as the "screw-worm fly" is well known in the west. It is one of the most important of the insects which affect domestic animals and its greatest damage is done in Texas and adjoining States. The fly lays its eggs on any spot where the skin has been injured either from a scratch by a barbed-wire fence or the puncture of a thorn. The raw or slightly bloody surface attracts the flies which lay their eggs and the larvae live in the flesh, making a large sore. The fly does not confine its attacks to domestic animals but also frequently attacks man. The most common cases are those where the fly has laid its eggs in the nostrils of some one, generally some person with a bad catarrhal trouble. The eggs hatch and the larvae work their way through the upper nostrils and destroy the tissues. The soft palate is frequently entirely destroyed and fatal cases in men are not rare. The remedy is to syringe out the nasal passages with diluted carbolic acid. This insect also in its larval stage feeds on carrion. Another well known flesh-fly is Lucilia caesar, generally known as the green-bottle fly, which is sometimes driven into houses on the approach of a storm. The large blue-bottle fly of rather dull color with black spines on the thorax is known as Calliphora erythrocephala. This is the common "blow-fly" of Europe and is the species treated by Lowne in his classic "Anatomy of the Blow-Fly." Its larvae are indistinguishable from those of the preceding species except in size and they are to be found on meat and dead animals. Riley states also that it destroys the Rocky Mountain locust or western grasshopper. The flies of the true genus Sarcophaga are very general scavengers, feeding, however, upon animal matter practically exclusively. The common flesh-fly of Europe Sarcophaga carnaria does not seem to occur in this country but we have a closely allied species, S. sarraceniae, which has been reared from larvae found feeding upon dead insects in the pitchers of the common pitcher plants and which is often reared from dead insects and from excrement. It is rather a rapid breeder and a generation will be developed in ten days in the summer time.

Among the commonest of the flesh-flies are the small species of the genus Helicobia, originally so named because they were reared from a dead snail. They are very commonly found feeding in the larval stage upon the dead bodies of insects.

A majority of the flesh-flies belong to what may be termed the house-fly type, i. e., they are gray flies rather obscurely striped with black, but some of them, as just shown, may become metallic in color.