Lice

Three species of lice occur as parasites on humans. These lice are blood suckers, and they can be disconcertingly abundant under unsanitary conditions. The human louse, Pediculus humanus, occurs as two races, which feed on different parts of the body. The head louse, capitis race, occurs in the hairs of the head, to which it attaches its whitish eggs, also known as "nits." The body louse corporis race, also known as the "cootie," feeds on the human body, and hides and lays its A chewing louse. JLM Visuals. Reproduced by permission.
eggs in clothing. Bites from human lice are irritating, and they can become infected. Human lice are also important as vectors of some deadly diseases, such as typhus, relapsing fever, and trench fever, which are transmitted to humans through scratching the bodies or feces of infected lice into the skin.

The crab louse Phthirus pubis is another parasite of humans, which occurs in the coarser hair of the under-arms and genital area.

Lice infestations of humans are still commonly treated by dusting the body with an insecticide such as DDT, which is still the preferred chemical for this relatively restricted usage. Clothing may also be washed in an insecticidal solution, and living areas must be fumigated with an insecticide or steam. The eggs of head lice are relatively resistant to many chemical treatments, and they may have to be removed using a fine-toothed comb, and then killed by crushing between the fingernails. This meticulous, pest-control procedure is sometimes known as "nit-picking."