in zoology, a genus of insects belonging to the order of diptera. It has no mouth; but three punctures, without trunk or beak: Antennæ taper, proceeding from a lenticular joint. There are five species.

1. Bovis, the breeze or gad-fly.—Thorax yellow, with a black transverse line between the wings: Abdomen tawny, with fine black transverse lines; last segment black: Wings white, with a brown transverse line, and three brown spots. Size of the large blue fly. Deposits its eggs under the skin on the backs of oxen, where the maggots are nourished the whole winter till the month of June; and plague the cattle so all the summer, that they are obliged to fly for refuge into the water, and dare not quit it the whole day.

2. The hemorrhoidalis.—Body long, black, covered with tawny hair; middle of the thorax less hairy; wings immaculate; antennæ very short: Length half an inch. Deposits its eggs in the rectum of horses, and occasions great torment. See BOVIS.

3. Ovin, the grey fly.—Spotted with black; front pale-yellow; legs brownish; wings with short black-veins: length half an inch. Breeds in the frontal sinus of sheep; where the maggots, hatched from the eggs, lodge the whole winter, vellicating the internal membranes, and often bringing on death.

4. The nasalis.—Body black; but the head, thorax, and abdomen, covered with pale-red hair, except the first segment of the latter, which is covered with white hair; the wings immaculate. Breeds in the fauces of horses, entering by their nose.

5. The tarandi.—Thorax yellow; with a black line between the wings, which are immaculate: Abdomen tawny, last segment black. Infects the back of the rein-deer, so as greatly to retard the breed. The rein-deer of Lapland are obliged every year to fly to the Alpine mountains, to escape the pursuit of these insects. insects: yet a fourth part of their number perish by them at two years old; the rest are emaciated, and have their skins spoiled. It is one of the most curious genera of insects. They are distinguished into several species, by reason of the different places wherein they deposit their eggs. Some, instructed by nature that their eggs cannot be hatched but under the skins of living creatures, such as bulls, cows, rein-deer, flags, and camels, fix upon them at the instant of laying their eggs. From the hinder part of their body issues a whimple of wonderful structure. It is a scaly cylinder, composed of four tubes, which draw out like the pieces of a spying-glass; the last is armed with three hooks, and is the gimlet with which the insect bore through the tough hides of horned cattle. The animal seems to experience no pain from the puncture, unless the insect, plunging too deep, attacks some nervous fibre; in which case, the beast runs about, and becomes furious. The eggs being hatched, the grub feeds on the matter of the wound. The place of its abode forms upon the body of the quadrupeds a bunch sometimes above an inch high. When full-grown, the larva breaks through the tumor, and slides down to the ground; for doing which it takes the cool of the morning, that it may neither be overpowered by the heat of the day, nor chilled by the cold of the night: it then digs itself a burrow, into which it retires. Its skin grows hard, and turns to a very solid shell. There it is transformed to a chrysalis, and afterwards to a winged insect. Nature has provided for every exigence: the shell wherein the oestrus is inclosed, is of so strong a texture that it could not make its way out, if at one of the ends there were not a small valve, fastened only by a very slight filament. The first push the oestrus makes, the door gives way and the prison opens. The insect wings its way to woods and places frequented by cattle.