After what period do lice multiply? - briefly
Lice develop from egg to reproducing adult in roughly two weeks, with eggs hatching in 7–10 days and the new adult beginning to lay eggs about 14 days after the original egg is deposited. Consequently, a full reproductive cycle repeats approximately every 7–10 days.
After what period do lice multiply? - in detail
Lice develop through a predictable sequence of stages: egg (nit), three nymphal instars, and adult. Each stage requires a specific amount of time before the next can be reached, and the whole cycle determines how quickly a population expands.
- Egg incubation: 7–10 days at around 30 °C (cooler temperatures lengthen this phase to 10–14 days).
- Nymphal development: three molts over 9–12 days, each molt lasting roughly 3–4 days.
- Maturation to reproductive adult: occurs 2–3 days after the final molt.
A mature female lays 3–5 eggs per day, potentially depositing up to 100 eggs during her lifetime of about 30 days. Consequently, a new generation appears roughly every two weeks, and under optimal conditions the number of lice can double in 4–5 days.
Factors that modify these intervals include ambient temperature, host‑to‑host contact frequency, and the availability of blood meals. Lower temperatures can extend the full cycle to 14–21 days, while high crowding and frequent feeding accelerate development.
Because the first reproductive adults emerge within 10–14 days after an initial infestation, effective control measures must be timed to target both existing lice and newly hatched nymphs before they reach maturity. Re‑treatment intervals of 7–10 days are commonly recommended to interrupt the cycle and prevent population resurgence.