How are lice born in humans? - briefly
Human lice develop from eggs (nits) that adult females cement to hair shafts; the eggs incubate for roughly 7–10 days before hatching into nymphs, which mature after several molts.
How are lice born in humans? - in detail
Human lice reproduce through sexual mating followed by oviposition on the host’s hair or body hair. Adult females locate a suitable site, usually close to the scalp or the base of body hair, and use a specialized abdominal gland to secrete a cement‑like substance that secures each egg to the shaft. An individual female can lay five to ten eggs daily, reaching a total of roughly one hundred over her lifespan.
The egg, commonly called a nit, contains a developing embryo protected by a chorion. Embryogenesis proceeds at the host’s surface temperature (approximately 32–35 °C) and requires adequate humidity. Within 7–10 days, the embryo completes segmentation, organogenesis, and formation of appendages. The operculum at the pole opens, allowing the first nymphal stage to emerge.
Nymphs undergo three successive molts, each lasting about 3–4 days. After the final ecdysis, the insect reaches the adult stage, capable of reproduction. The complete cycle—from egg deposition to mature adult—takes roughly three weeks under optimal conditions.
Key biological details:
- Mating: Males mount females, insert the aedeagus into the female’s genital opening, and transfer sperm. Copulation lasts only a few minutes.
- Egg attachment: Cement glands produce a proteinaceous glue that hardens within seconds, preventing dislodgement by washing or combing.
- Incubation temperature: Development accelerates at higher temperatures; at 37 °C, hatching may occur in as few as six days, while cooler conditions prolong the period.
- Humidity requirement: Relative humidity above 50 % is essential for successful embryogenesis; low humidity leads to desiccation of eggs.
- Species variation: Head lice (Pediculus humanus capitis) lay eggs on scalp hair; body lice (Pediculus humanus corporis) deposit eggs on clothing fibers; pubic lice (Pthirus pubis) attach eggs to coarse pubic hair, each with similar reproductive mechanisms but differing preferred habitats.
Understanding each phase of the life cycle clarifies how lice propagate on human hosts and informs effective control strategies.