An insect (order Phthiraptera) that lacks wings and eyes and in which several other structures are greatly reduced. All lice are obligate parasites of birds and almost all mammals, feeding on skin debris, feathers, skin secretions, or blood. Eggs (nits) are attached to the hair, fur, or feathers of the host. There are about 5000 species. Humans host the head louse (Pediculus humanus capitis), body louse (P. h. humanus), and pubic louse (Pthirus pubis).