Human lice are tiny, wingless insects that live only on people and come in two forms: the head louse in hair and the body louse in clothing. Head lice are among the most common childhood pests in the US, with an estimated 6–12 million infestations a year among kids ages 3–11. Head lice don't spread disease, but body lice can.
Appearance
- Appearance
- Adults are about 1/12–1/6 in (2–4 mm) long; head lice are a bit smaller, around the size of a sesame seed. They are flat, wingless, and grayish, turning reddish after a blood meal. Clawed legs let them grip hair or fabric tightly.
Look-alikes
Crab LousePthirus pubis
Crab lice are smaller (1.1–1.8 mm) and short and broad, like a tiny crab. They live mainly in pubic hair, so lice found on the head are almost always head lice.
Why they get mixed upBoth are tiny blood-feeding lice found in human hair.
Where it lives
- Typical habitats
- human hair
- clothing and bedding
- Range
- Found wherever people live, including throughout the US.
- Preferred conditions
- Head lice live close to the scalp, often behind the ears and at the back of the head. Body lice hide in the seams of clothing and bedding and visit the skin only to feed.
Behavior
- Diet
- Human blood only, several times a day, at every stage except the egg.
- Activity
- Lice crawl; they can't hop or fly. Head lice spread mainly through head-to-head contact, less often through shared hats, combs, or bedding. Pets don't get or spread human lice. Lice can survive underwater for hours, and pool chlorine doesn't kill them.
Life cycle
- Reproduction
- Females glue eggs () to the hair shaft close to the scalp, or to clothing fibers. Eggs hatch in 6–9 days, and the young molt three times before becoming adults.
- Lifespan
- About 30 days on a person; one to two days if it falls off.
Cautions
- Cautions
- Bites cause itching. Head lice don't transmit disease. Body lice can spread epidemic typhus, trench fever, and relapsing fever.
Name and classification
- About the name
- Head lice (P. h. capitis) and body lice (P. h. humanus) look nearly identical and are usually treated as two . They can interbreed in the lab but keep to different places on the body. Some experts treat them as separate species.
Conservation
- IUCN Red List
- NENot EvaluatedNot yet assessed
Culture and stories
- Culture and stories
- In the US, head lice are much less common among African Americans than among other groups.
- Body lice are sometimes called "cooties." In the US today they mostly affect people without regular access to bathing and clean clothes.
- Because head and body lice split apart around the time people began wearing clothes, scientists have used them to estimate when clothing first appeared, though this idea is debated.
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