After how long do lice reproduce on the head? - briefly
Lice become sexually mature about one week after their final molt, and a fertilized female starts depositing eggs 7‑10 days later, making the complete reproductive cycle roughly 14 days. Consequently, a new generation can emerge within two weeks of initial infestation.
After how long do lice reproduce on the head? - in detail
Head lice (Pediculus humanus capitis) complete their reproductive cycle on a human scalp in roughly three weeks. The process begins when a fertilized egg, called a nit, is attached to a hair shaft near the scalp. Under normal body‑temperature conditions (≈ 37 °C), the egg hatches after 7–10 days.
The emerging nymph enters a developmental phase that lasts about 9–12 days. During this period the insect undergoes three successive molts, each requiring a blood meal. Nymphs are smaller than adults and cannot lay eggs, but they become sexually mature after the final molt.
An adult female can begin oviposition within 2–3 days of mating. She typically deposits 4–5 eggs per day, spacing them about 1 mm from the scalp to maintain optimal temperature and humidity. A single female may lay 50–100 eggs over her lifespan, which averages 30 days. Eggs laid by the first generation will hatch after another 7–10 days, initiating the next cycle.
Typical timeline for one generation
- Egg (nit) stage: 7–10 days until hatching.
- Nymph stage: 9–12 days, encompassing three molts.
- Adult stage: reproductive maturity reached 2–3 days after the final molt; egg‑laying continues for ~ 3 weeks.
Thus, from the moment a fertilized egg is placed on a head to the appearance of a new cohort of reproductive adults, the interval is approximately 21–25 days. This rapid turnover explains why infestations can expand quickly if untreated.