How long does a louse develop from an egg? - briefly
A head‑louse egg typically hatches in 7‑10 days, with higher temperatures shortening the period. After emergence, the nymph matures to an adult in another 9‑12 days, giving a total development time of roughly 16‑22 days.
How long does a louse develop from an egg? - in detail
The life cycle of a human louse proceeds through four distinct phases: egg, three successive nymphal instars, and adult. The total interval from oviposition to a reproducing adult depends on species, ambient temperature, and relative humidity.
Egg stage
- Female deposits a nit on a hair shaft or clothing fiber.
- Incubation lasts 7–10 days at 30 °C (86 °F); at 20 °C (68 °F) the period extends to 10–14 days.
- High humidity (≥70 %) shortens development; low humidity prolongs it.
Nymphal stages
- Three molts occur, each producing a nymph that resembles the adult but is smaller and not yet capable of reproduction.
- Each instar requires 1–2 days under optimal conditions (30 °C, 70 % humidity).
- The cumulative nymphal period therefore ranges from 3 to 6 days.
Adult stage
- After the final molt the insect reaches sexual maturity.
- Adults live 30–45 days on a host, during which females lay 6–10 eggs per day.
Species variations
- Head louse (Pediculus humanus capitis): complete cycle averages 10–14 days at typical indoor temperatures (22–25 °C).
- Body louse (Pediculus humanus humanus): similar timing, but eggs are laid on clothing; development may be slightly slower if garments are infrequently changed.
- Pubic louse (Pthirus pubis): egg incubation 7–10 days; nymphal stages each 2–3 days, giving a total of about 12–15 days to adulthood.
Temperature is the primary factor influencing speed; each 5 °C increase can reduce the overall developmental period by roughly 20 %. Humidity modulates egg viability but has a lesser effect on the duration of nymphal molts.
In summary, under favorable conditions a louse progresses from egg to adult in approximately 10–14 days, with the exact timeline dictated by environmental parameters and species‑specific biology.