How do lice reproduce and how long do they live?

How do lice reproduce and how long do they live? - briefly

Female lice lay 1–10 eggs daily, securing each to a hair shaft; the eggs hatch in 7–10 days and the nymphs mature into adults after an additional 9–12 days. Adult lice survive on a host for roughly 30 days before dying.

How do lice reproduce and how long do they live? - in detail

Lice reproduce sexually. Adult females mate shortly after reaching maturity, typically within a few days of their final molt. Mating occurs on the host’s hair or body surface, where the male grasps the female’s abdomen and transfers sperm through the genital opening. After insemination, a female deposits eggs—commonly called nits—onto hair shafts or clothing fibers. Each egg is cemented with a proteinaceous glue that hardens within minutes, securing it close to the scalp or skin.

Key aspects of the reproductive cycle:

  • Egg stage: 5–7 days at 30 °C; longer at cooler temperatures. Eggs are oval, 0.8 mm long, and contain a developing embryo.
  • Nymphal stages: Three molts occur, each lasting 3–4 days. Nymphs resemble miniature adults but lack fully developed reproductive organs.
  • Adult stage: Emerges after the third molt. Females begin laying eggs within 1–2 days, producing 5–10 eggs per day and up to 100 over their lifespan.

Lifespan varies among species and environmental conditions:

  • Head lice (Pediculus humanus capitis): Adults live 30–45 days on a human host. Nymphs develop to adulthood in 9–12 days, making the complete cycle roughly 3 weeks under optimal warmth.
  • Body lice (Pediculus humanus corporis): Adults survive 30–40 days; eggs hatch in 6–10 days. The entire cycle can be completed in 2–3 weeks.
  • Pubic lice (Pthirus pubis): Adults live 30–40 days; eggs hatch in 7–10 days. Full development from egg to adult occurs in about 2–3 weeks.

Survival outside the host is limited. Eggs remain viable for up to 10 days in a dry environment, while nymphs and adults cannot endure more than 24 hours without a blood meal. Temperature and humidity critically influence development speed; higher warmth accelerates egg hatching and nymphal growth, reducing the overall cycle duration.

In summary, lice follow a rapid, temperature‑dependent life cycle: mating, egg deposition, three successive nymphal molts, and a brief adult phase lasting roughly one month, during which females generate a substantial number of eggs to sustain the population.