How do lice reproduce in hair? - briefly
Female head lice attach 5‑10 eggs (nits) to the hair shaft close to the scalp; the eggs hatch in 7‑10 days. The resulting nymphs mature in about nine days and then mate, completing the reproductive cycle within three weeks.
How do lice reproduce in hair? - in detail
Head lice (Pediculus humanus capitis) reproduce exclusively on the host’s scalp, where the warm, humid environment supports rapid development. Female adults attach their eggs to individual hair shafts using a cement secreted from the abdomen. Each female lays 5–7 eggs per day, up to 100 over her lifetime, and the eggs (nits) are positioned within 1 mm of the scalp to maintain optimal temperature for embryogenesis.
The incubation period lasts 7–10 days, after which the embryo hatches into a nymph. Nymphs resemble miniature adults but lack fully developed reproductive organs. They undergo three successive molts, each lasting approximately 2 days, before reaching sexual maturity. The complete life cycle—from egg to fertile adult—takes about 21 days under typical indoor conditions (20–30 °C, 70–80 % relative humidity).
Mating occurs shortly after the final molt. Male lice locate females by detecting chemical cues on the cuticle. Copulation lasts a few minutes, during which the male transfers sperm via a specialized intromittent organ. Females store sperm in a spermatheca, allowing continuous egg production without repeated mating.
Key temporal parameters:
- Egg laying: 5–7 per day, total ≈ 100
- Egg incubation: 7–10 days
- Nymphal development: three instars, each ≈ 2 days
- Time to reproductive maturity: ≈ 9 days post‑hatch
- Adult lifespan: 30–40 days on a host
Reproductive output is limited by host grooming and environmental conditions. Regular removal of nits and thorough combing reduce the number of viable eggs, interrupting the cycle before females can complete their oviposition schedule.