How many lice hatch from one nit? - briefly
A nit holds a single egg, which hatches into one nymph that later becomes an adult louse. Consequently, each nit produces one louse.
How many lice hatch from one nit? - in detail
A nit is the egg of the human head louse, deposited on hair shafts and cemented with a protein matrix. The embryonic development lasts 7‑10 days under optimal conditions (temperature ≈ 30 °C, relative humidity ≈ 70 %).
In controlled laboratory studies, hatch success consistently reaches 80‑95 % of deposited eggs. Consequently, each viable nit produces a single emerging nymph; the egg contains only one embryo, and twin or multiple hatchlings are extremely rare and regarded as anomalies.
Factors influencing the proportion of eggs that successfully hatch include:
- Ambient temperature: lower than 25 °C prolongs development and reduces viability; above 35 °C increases mortality.
- Relative humidity: below 40 % causes desiccation of the embryo; above 80 % promotes fungal contamination.
- Host hair characteristics: dense, oily hair improves attachment and reduces mechanical loss of eggs.
- Chemical exposure: insecticidal treatments or pediculicidal shampoos can penetrate the cement and kill embryos before emergence.
Field observations on infested populations corroborate laboratory data: the average number of lice emerging from a single nit does not exceed one, with occasional non‑viable eggs accounting for the small discrepancy between total eggs laid and hatched nymphs.
Therefore, under normal environmental and host conditions, a single nit yields one living louse; hatch rates approach ninety percent, and deviations arise mainly from adverse temperature, humidity, or chemical interventions.