How long does a human louse live? - briefly
A human head louse usually lives for roughly 30 days when it can feed regularly; without a blood meal it expires within 1–2 days.
How long does a human louse live? - in detail
Human body lice (Pediculus humanus corporis) typically survive for 30 days on a host. Adult females lay 5–10 eggs per day; each egg (nit) hatches in 7–10 days. Nymphs undergo three molts, requiring about 9–12 days to reach maturity. Under optimal conditions—temperature 30 °C, humidity 70 %—the full life cycle from egg to adult spans roughly 18–21 days. Adults that lose contact with a host die within 2–3 days, as they cannot survive more than 48 hours without blood. In contrast, head lice (Pediculus humanus capitis) share a similar developmental timeline: eggs hatch in 7–10 days, nymphal stages last 9–12 days, and adults live 30 days on a human scalp, dying after 1–2 days off‑host. Environmental extremes shorten survival; temperatures above 40 °C or below 0 °C can kill all stages within hours. Factors influencing longevity include host grooming frequency, use of insecticidal treatments, and the lice’s access to blood meals.
Key points summarizing lifespan:
- Egg incubation: 7–10 days
- Nymphal development (three instars): 9–12 days total
- Adult longevity on host: ~30 days
- Survival without host: 1–3 days, depending on species and conditions
- Complete life cycle: 18–21 days under optimal climate
Understanding these parameters aids in timing interventions and predicting infestation dynamics.