Chewing and Sucking Lice: Phthiraptera

Physical characteristics: The body of this louse is gray, longer than wide, and measures 0.078 to 0.12 inches (2 to 3 millimeters) in length. The head has distinctive dark eyes. Their abdomens lack distinct bumps. The head louse is usually 20 percent smaller than the body louse.

Geographic range: This species is found worldwide. It is an ectoparasite of humans but is also found on gibbons and New World monkeys.

Habitat: Two forms exist. Head lice are found on the human scalp. Body lice prefer clothing and the human chest and stomach.

Diet: Both head and body lice feed on blood.

Behavior and reproduction: Head lice feed regularly every few hours, while body lice feed only once or twice per day when the host Head lice attach their eggs to the base of hair shafts. Eggs hatch in five to seven days. (©Eye of Science/Photo Researchers, Inc. Reproduced by permission.) is resting. Both forms are capable of adapting to the different ecological conditions on the human scalp, body, or clothing. They carry several important human diseases.

Head lice attach their eggs to the base of hair shafts. Body lice glue their eggs to hairlike fibers of clothing worn by the host. Eggs hatch in five to seven days. The larvae reach adulthood in ten to twelve days.

Human head/body lice and people: This species, also known as cooties or gray backs, was called "mechanized dandruff" by American soldiers during World War II. The body louse spread epidemic typhus that resulted in the death of hundreds of millions of people up to the early 1900s. Since World War II, large outbreaks of this disease have occurred in Africa, mostly in Burundi, Ethiopia, and Rwanda. The head louse can be common in children. Up to one out of five students are infested in some primary schools in parts of Australia, the United Kingdom, and the United States. Head lice are not normally known to transmit disease.

Conservation status: This species is not endangered or threatened. However, populations found on small, isolated human tribes and non-human hosts are probably threatened with extinction due to declining host populations and habitat loss. ∎