How do lice reproduce in humans? - briefly
Female head lice attach their eggs (nits) to hair shafts, laying 5–8 per day; the eggs hatch in 7–10 days, and the nymphs become sexually mature after another 7–10 days. Mating occurs soon after nymphal emergence, so the entire reproductive cycle repeats roughly every three weeks.
How do lice reproduce in humans? - in detail
Human lice, specifically Pediculus humanus capitis (head louse) and Pediculus humanus corporis (body louse), reproduce exclusively on the host’s scalp or clothing. A fertilized female lays 6‑10 eggs (nits) per day, attaching each to a hair shaft or fabric fiber about 1 mm from the scalp. The attachment uses a cement-like protein that hardens within minutes, preventing displacement.
The egg incubation period lasts 7‑10 days at typical body‑temperature conditions. Upon hatching, the emerging nymph resembles an adult but is smaller and lacks full reproductive capacity. Nymphal development proceeds through three molts, each requiring approximately 3‑4 days. After the final molt, the adult emerges, fully capable of mating.
Mating occurs shortly after the adult stage is reached. Males locate females by detecting chemical cues emitted by the female’s cuticle. Copulation lasts a few minutes, during which the male transfers a spermatophore to the female’s reproductive tract. A single mating event provides sufficient sperm for the female to produce multiple batches of eggs over her lifespan.
Key points of the reproductive cycle:
- Egg (nit) deposition: 6‑10 per day, firmly cemented.
- Egg incubation: 7‑10 days at ~37 °C.
- Nymphal stages: three instars, each 3‑4 days.
- Adult maturation: ~10 days from egg to reproductive adult.
- Mating: brief, once sufficient sperm stored for continuous oviposition.
- Total reproductive output: up to 300 eggs per female over 30‑40 days.
Environmental factors such as temperature, humidity, and host grooming affect each stage’s duration and survival rate. Adequate control measures target the egg attachment phase, the nymphal molts, or the adult population to interrupt the cycle.