How quickly do lice multiply? - briefly
A female head louse deposits 3‑5 eggs daily, and the eggs hatch in 7‑10 days; each newly emerged adult can begin laying within a week. Consequently, under favorable conditions a lice colony can double roughly every 7‑10 days.
How quickly do lice multiply? - in detail
Lice develop through three stages: egg, nymph, and adult. A fertilized female lays 6‑10 eggs (nits) per day, attaching them to hair shafts near the scalp. Incubation lasts 7‑10 days at typical indoor temperatures (20‑25 °C). After hatching, nymphs undergo three molts over 4‑6 days before reaching reproductive maturity. Consequently, an adult female can produce roughly 30‑40 viable offspring within a single week.
Population expansion follows an exponential pattern. Assuming optimal conditions and no intervention, one pair can generate about 150‑200 individuals within three weeks, because each new adult contributes its own egg output. The generation time—from egg to reproductive adult—is roughly 10‑12 days, allowing at least two full cycles per month.
Factors that accelerate growth include:
- Warm, stable ambient temperature (above 20 °C)
- High humidity, which improves egg viability
- Frequent head-to-head contact, facilitating transmission of newly hatched nymphs
Conversely, lower temperatures, reduced humidity, and regular grooming slow the cycle by extending egg incubation and nymph development.
In practical terms, an untreated infestation can double its size every 5‑7 days, reaching a noticeable level within two to three weeks. Prompt removal of nits and treatment of adults are essential to interrupt this rapid reproductive rhythm.