How do lice reproduce in the head? - briefly
Female head lice lay 5–7 eggs daily, attaching each to a hair shaft near the scalp with a cement‑like secretion; the eggs hatch in roughly 7 days, releasing nymphs that become adults after an additional 9–10 days. Mating occurs soon after adult emergence, enabling rapid population growth.
How do lice reproduce in the head? - in detail
Head lice (Pediculus humanus capitis) reproduce exclusively on the human scalp. Adult females lay eggs, known as nits, near the hair shaft base. Each female can deposit up to eight eggs per day, attaching them with a cement‑like secretion that hardens within minutes. Eggs remain attached for 7–10 days; during this period embryonic development proceeds, culminating in hatching of a first‑instar nymph.
The life cycle proceeds through three successive nymphal stages. After emerging, a nymph feeds on blood for 1–2 days before molting to the second instar. The second instar feeds for another 2–3 days, then molts to the third instar. The third‑instar feeds for 3–4 days before reaching full adult size. The total interval from egg to adult ranges from 9 to 14 days, depending on temperature and host conditions.
Adult lice become sexually mature within 24–48 hours of their final molt. Mating occurs on the host’s hair, with the male grasping the female’s abdomen using his forelegs. Copulation lasts several minutes, after which the female resumes oviposition. The adult lifespan is approximately 30 days, during which a single female may lay 100–150 eggs, ensuring rapid population growth if untreated.
Key parameters influencing reproduction:
- Temperature: optimal development at 30–32 °C; lower temperatures extend developmental periods.
- Host hygiene: removal of nits or frequent washing reduces egg survival.
- Blood availability: uninterrupted feeding is essential for egg production; starvation halts oviposition.
Understanding these biological details enables targeted control measures that interrupt the reproductive cycle at the egg, nymph, or adult stage.