The Cephalemyia (Œstrus) ovis is to be found in Europe, Arabia, Persia, and in the East Indies. It lays its eggs on the edges of the animal's nostrils, and the larva lives in the frontal and maxillary sinuses. It is a whitish worm, having a black transverse band on each of its segments. Its head is armed with two horny black hooks, parallel, and capable of being moved up and down and laterally. Underneath, each segment of the body has several rows of tubercles of nearly spherical form, surmounted by small bristles having reddish points, and all of them bent backwards. "These points," says M. Joly, "probably serve to facilitate the progress of the animal on the smooth and slippery surfaces of the mucous membranes to which it fixes itself to feed, and perhaps also to increase the secretion of these membranes by the irritation occasioned by the bristles with which they are furnished." [16]
Fig. 50.—Conops.
Fixed by means of these hooks to the mucous membrane, which it perforates, the larva nourishes itself with mucus, and lives in this state, according to M. Joly, during nearly a whole year. At the end of this time it comes out, following the same course by which it entered, falls to the ground, and burying itself to the depth of a few inches, is transformed into a pupa. The cocoon is of a fine black colour. Thirty or forty days after its burial it emerges in the perfect state, and detaching the lid at the anterior end of the cocoon by the aid of its head, which has increased considerably in size, takes flight.
Notwithstanding the formidable appearance of their trunks, the habits of the perfect Conopes ([Fig. 50]) are very quiet. In the adult state they are only to be seen on flowers, of which they suck the honeyed juice. But with their larvæ the case is otherwise. These latter live as parasites on the humble-bees (Bombi). Latreille saw the Conops rufipes issue in the perfect state from the body of a humble-bee, through the intervals of the segments of the abdomen.
The Mucides form that great tribe of Diptera commonly known as flies, and which are distributed in such abundance over the whole world. Faithful companions of plants, the flies follow them to the utmost limits of vegetation. At the same time they are called upon by Nature to hasten the dissolution of dead bodies. They place their eggs in the carcases of animals, and the larvæ prey upon the corrupt flesh, thus quickly ridding the earth of those fatal causes of infection to its inhabitants. The organs of these insects are also infinitely modified, in order to adapt them to their various functions.