Lice are very small, flat, wingless insects. They can neither jump nor fly. Their color ranges from pale tan or dirty white to grayish black. Their legs are short and stout, with a claw on each leg for grasping and holding onto hair. Lice have retractable piercing and sucking mouth parts.
Human blood is their only source of nourishment.
Lice are spread by sharing infested clothing, hats, scarves, combs, hair brushes, and head gear, or as a result of close physical contact with an infested person. Other occasional sources are bedding, furniture, rugs, and floor surfaces where dislodged lice may be present. Once infested, an individual usually harbors only a few dozen lice. But some people have been known to carry several hundred lice and, occasionally, a few thousand. Lice are more host-specific than ticks and fleas.