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.

3. Ovis, 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. Infest 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 the Alpine mountains, to escape the pursuit of these insects: yet a fourth part of their number perish by them at two years old; the rest are emaciated, and have their skins spoiled.