Human Lice


Lice are wingless parasites that feed on blood. There are more than 3,000 louse species found worldwide. The most common types of human lice are head lice, body lice and crab lice. 

Pest Stats


Dirty white to grayish black




Long, flat body


Adults are small, about 1/16-1/8” (2-4.2 mm) long




Found throughout the United States

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Head lice: Female head lice lay 50-100 oval eggs, which are individually cemented to a head hair near the scalp. Eggs require high humidity and warmth in order to develop and hatch. Eggs hatch in 5-10 days and the first nymph must feed by sucking the blood from a scalp within 24 hours or it will die. The life cycle takes about 3 weeks. Adult head lice usually live for 22-23 days. In general, head lice can survive no more than 48 hours without a host.

Body lice: Body lice move from clothing to adjacent areas of the body to feed, only when the infested person is resting. Female body lice lay about 200 oval eggs, or nits, that are individually cemented to a clothing fiber. The eggs tend to be laid in large numbers along the seams of underwear and in places where clothing is in contact with the body, such as the neck, shoulder, armpit and waist. Because eggs are removed with the clothing, development and hatch times are dependent on room temperature. The life cycle takes about 2-4 weeks if clothing is removed at night. Adult body lice live up to 29 days.

Crab lice: Crab lice cannot survive more than 24 hours off a host. The female lays 15-50 whitish eggs over her lifetime. Each egg is individually cemented to a coarse hair near the skin. Eggs hatch in 7-8 days with feeding beginning in 1-2 hours. The life cycle requires about 5-6 weeks. Adult crab lice live for about 15-25 days. 


Head lice: Head lice live continuously on the head area unless dislodged by scratching. They are typically found in hair above the ears and on the back of the scalp. They are often transmitted from person-to-person by the direct contact of two heads, or by sharing items, such as brushes, combs, hats and towels. Head lice are common in crowded places, such as elementary schools. 

Body lice: Body lice live on clothing, especially items made of wool. Female body lice are often found along clothing seam where they lay eggs. Male body lice tend to be distributed over the inside of the clothing, but further away from the body. Body lice are transmitted one person to another by the sharing of infested clothing or bedding.

Crab lice: Crab lice are usually found in areas of the body containing hair, such as beards, eyebrows, armpits and the pubic region. Crab lice are not as common in places such as schools, since they can only be spread through direct physical contact.


Lice are not really considered a health threat, but their bites often result in excessive itching and redness. Frequent scratching may cause open sores or a skin infection.