itch mite

noun

: any of several minute parasitic mites that burrow into the skin of humans and animals and cause itch

especially : a mite of any of several varieties of a species of the genus Sarcoptes (S. scabiei) that causes the itch, is about ¹/₆₀ inch (0.4 millimeter) long, and has a round-ovate body and 3-jointed legs and mandibles resembling minute needles