How do lice emerge from the head? - briefly
After the egg (nit) hatches, the nymph climbs onto the scalp and positions itself on a hair shaft. It secures itself with hooked claws and starts feeding on blood.
How do lice emerge from the head? - in detail
Lice complete their development on the human scalp, passing through three stages: egg (nit), nymph, and adult. The transition from the immature forms to mobile insects involves several distinct steps.
When the female deposits an egg, she secures it to a hair shaft with a cement‑like substance. The egg remains attached for about 7–10 days, during which the embryo matures inside a transparent shell. Temperature and humidity on the scalp regulate the incubation period; optimal conditions accelerate development, while low humidity can delay hatching.
At the end of the incubation phase, the nymph emerges by breaking the operculum, a small cap at one end of the egg. The emerging nymph is a miniature version of the adult, lacking fully developed reproductive organs and wings (lice are wingless). Immediately after emergence, the nymph begins to feed on blood, which is essential for molting.
The nymph undergoes three successive molts, each lasting 3–4 days. After each molt, the insect grows larger and its exoskeleton hardens. Throughout the molting process, the lice remain attached to hair shafts, moving only short distances to locate a suitable feeding site.
Approximately 9–12 days after the first emergence, the insect reaches adulthood. Adult lice are capable of reproduction and can lay up to 5 eggs per day. They remain on the scalp, moving quickly through hair to avoid detection and to locate blood sources. The cycle repeats as long as the host provides a suitable environment.
Key factors influencing the emergence and survival of lice:
- Scalp temperature (≈ 34–36 °C) maintains metabolic activity.
- Relative humidity (≥ 30 %) prevents desiccation of eggs and nymphs.
- Availability of blood meals sustains growth and reproduction.
- Grooming habits (e.g., combing, shampooing) can disrupt attachment and reduce population density.
Understanding each phase of the life cycle clarifies how lice transition from immobile eggs to active insects on the human head.