IIIPPOBOSCA, in natural history, a genus of insects of the order Diptera. Mouth with a short cylindrical, straight, two-valved sucker; the valves are equal ; antennae filiform ; feet armed with nume rous claws ; body flat and hard; stemma. to none. There are five species, of which the most familiar is H. equina, or horse. fly ; head brown ; thorax brown, varied with pale colour ; wings crossing each other, hyaline with a brown spot near the outer margin ; legs annulate with yellow and brown. This insect is exceedingly troublesome to horses : it hides itself un der the hairs, and fixes to the skin by means of their crooked nails. It varies in size, in different districts, but is largest in the southern and warm climates. The skin of the insect is of a strong and coria ceous nature; hence it may be pressed to a considerable degree, without being ap parently injured. The female of this in
sect deposits a single egg at distant inter vals ; but as the egg undergoes no further alteration of form, it has been regarded rather as a pupa than an egg; and, if i opened after a certain period, exhibitg the fly in its unadvanced state, and of a white colour. It not unfrequently lies during the whole winter in this state, the fly emerging in the following summer. II, avicularia is observed on the bodies of various birds, which it infests. H. hirun dinis is, as its name imports, to be found in the nests and on the bodies of swallows, swifts, and martins. H. ovina is without wings ; it is known by the name of the sheep-tick, and is found imbedded in the wool of these animals; this is so tenaceous of life, that it has been found in wool that has been a long time packed up in fleeces.