Sheep-louse, or SHEEP-TICK, or (in Scotland) KAID (Melophagus ovinus), an insect of the family Hippoboscidae, to which also the Forest Fly belongs, ranked in the order Diptera, although in this genus the wings are completely wanting. It lives among the wool of sheep, particularly of lambs, sucking the blood of the animal, and is most abundant in the early part of summer. Where it fixes its head in the skin a round tumour is formed. The body of the insect is compressed and smooth, of a rusty is not a tick proper, not being one of the Ixodidae. See TICK.