How do lice reproduce on a human head? - briefly
Female head lice deposit eggs (nits) on hair shafts near the scalp, where they hatch in 7‑10 days; the emerging nymphs feed on blood and mature to reproductive adults after about another week.
How do lice reproduce on a human head? - in detail
Lice that inhabit the human scalp belong to the species Pediculus humanus capitis. The reproductive cycle proceeds through several distinct stages: egg (nit), nymph, and adult. Adult females lay eggs directly onto hair shafts, securing each egg with a cement‑like substance that hardens within minutes. An average female deposits 5–10 eggs per day and can produce up to 150 eggs over her lifespan of approximately three weeks.
The incubation period for eggs depends on ambient temperature and humidity. Under typical scalp conditions (≈30 °C, 70 % relative humidity), hatching occurs after 7–10 days. Emerging nymphs resemble miniature adults but lack fully developed reproductive organs. They undergo three successive molts, each lasting about 2–3 days, before reaching sexual maturity. The complete nymphal development therefore spans roughly 9–12 days.
Once mature, adult lice mate shortly after the final molt. Mating occurs on the host’s hair, with the male clasping the female’s abdomen and transferring sperm via the genital opening. Females become receptive to fertilization within 24 hours and begin oviposition immediately. Adult lice survive for 30–35 days on the host, during which time a single fertile female can generate a new generation, leading to exponential population growth if unchecked.
Key points of the reproductive process:
- Egg attachment: cement‑based fixation to hair shaft, resistant to washing.
- Egg incubation: 7–10 days under normal scalp conditions.
- Nymphal development: three molts over 9–12 days, culminating in sexual maturity.
- Mating: brief copulation on hair, followed by rapid fertilization.
- Oviposition: 5–10 eggs per day, up to 150 eggs per female lifetime.
Understanding each phase clarifies why infestations can expand rapidly and informs effective control measures that target specific stages, such as disrupting egg attachment or eliminating nymphs before they mature.