How long does a louse develop? - briefly
Development from egg to reproducing adult requires roughly 2–3 weeks, varying with temperature and species. Under optimal conditions, each of the three nymphal stages lasts about 3–5 days.
How long does a louse develop? - in detail
The developmental cycle of human lice proceeds through three distinct phases: egg, nymph, and adult. Each phase has a specific duration that depends on species, environmental temperature, and host conditions.
- Egg (nit): laid on hair shafts close to the scalp; incubation lasts 7–10 days at 30 °C. Lower temperatures extend the period to 12–14 days.
- Nymph: three successive molts occur, each lasting 3–4 days under optimal conditions. The total nymphal stage therefore requires 9–12 days.
- Adult: reaches reproductive maturity after the final molt; lifespan ranges from 30 days to several months, with females producing up to 5 eggs per day.
For the head louse (Pediculus humanus capitis), the complete cycle from oviposition to the emergence of a reproductive adult typically spans 20–30 days at body‑temperature conditions. The body louse (Pediculus humanus corporis) follows a similar timeline, though eggs are deposited in clothing fibers, slightly prolonging the incubation phase to 10–14 days.
Temperature exerts a pronounced effect: at 20 °C the entire cycle can exceed 40 days, whereas at 35 °C development may complete in under 15 days. Humidity influences egg viability but has limited impact on the duration of nymphal stages.
In summary, under standard human body temperature (≈30–33 °C) the full developmental period of lice ranges from three to four weeks, with variations attributable to environmental factors and species‑specific behaviors.