How does a head louse differ? - briefly
A head louse is a wingless, obligate ectoparasite that lives on the human scalp and feeds exclusively on blood, unlike body or clothing lice that inhabit other regions and may parasitize different hosts. It cannot jump and is transmitted mainly through direct head‑to‑head contact.
How does a head louse differ? - in detail
Head lice (Pediculus humanus capitis) are obligate ectoparasites that live exclusively on the scalp and hair shafts of humans. They are smaller than body lice (Pediculus humanus humanus), measuring 2–3 mm in length, and possess a narrower body and shorter, more pointed antennae. Their claws are adapted to grasp hair shafts, whereas body lice have broader claws suited for clinging to fabric fibers. Crab lice (Pthirus pubis) differ markedly in shape, with a broader, crab‑like body and a distinct set of claw dimensions that enable attachment to coarse pubic hair.
- Habitat: head lice remain on the scalp; body lice inhabit clothing seams and migrate to the skin to feed; crab lice occupy the genital region and other coarse body hair.
- Mobility: head lice crawl; they cannot jump or fly. Body lice also crawl but can survive longer off the host; crab lice are less mobile, relying on direct contact.
- Feeding pattern: head lice feed every 3–4 hours, taking small blood meals. Body lice feed less frequently, approximately once daily, while crab lice feed every few hours but on different body sites.
Reproductive traits also diverge. Female head lice lay 6–10 eggs (nits) per day, cementing them to the side of hair shafts within 1 mm of the scalp. Eggs hatch in 7–10 days, producing three nymphal instars that mature in an additional 9–12 days. Body lice deposit eggs on clothing, not directly on the host, and their developmental timeline is similar but extended by environmental temperature. Crab lice lay fewer eggs, attach them to hair shafts, and complete development in roughly 10 days.
Transmission routes reflect ecological distinctions. Head lice spread primarily through direct head‑to‑head contact; indirect spread via personal items (combs, hats) is less efficient because eggs adhere tightly to hair. Body lice transmit through contaminated clothing and bedding, surviving weeks off the host. Crab lice require intimate skin‑to‑skin contact for transfer. Control measures therefore differ: scalp‑targeted pediculicides and meticulous combing are effective for head lice, while laundering clothing at high temperatures and changing garments are essential for body lice; crab lice treatment combines topical agents with hygiene of the affected area.