What is the name of a parasite that lives on hair?

The correct answer is lice. Lice are ectoparasites that specifically inhabit the hair and feathers of mammals and birds. They feed on the blood or skin debris from their host, causing irritation and discomfort. Lice are characterized by their small size and their ability to grasp onto the hair shafts, which is why they're often found directly on the host.

Fleas, while also ectoparasitic, primarily live in fur or feathers, but they are not specifically adapted to cling to individual hairs in the same way that lice do. Mites are microscopic parasites that can live on the skin surface and within hair follicles, but they do not live exclusively on hair. Ticks are larger arachnids that attach to the skin of a host for feeding and are temporarily parasitic, rather than being associated with living on hair itself. Thus, lice stands out as the parasite that directly pertains to living on the hair of hosts.