How do lice make nits? - briefly
Female head lice deposit eggs by using a cement-like secretion to affix each egg firmly to a hair shaft near the scalp; the attached eggs, called nits, remain in place until hatching. This attachment ensures the eggs are protected and positioned for optimal development.
How do lice make nits? - in detail
Female head lice (Pediculus humanus capitis) possess a specialized reproductive system that enables rapid egg production. After mating, the female stores sperm in a spermatheca, allowing fertilization of successive oocytes without additional copulation. Each mature oocyte travels through the oviduct to the ventral abdomen, where a short, hardened tube—known as the ovipositor—extrudes it onto the host’s hair shaft.
The egg‑laying sequence proceeds as follows:
- The ovipositor positions the egg against the hair cuticle, usually within 1 mm of the scalp where temperature and humidity are optimal.
- The female deposits a gelatinous adhesive, often called “nits cement,” which hardens within seconds, anchoring the egg firmly to the strand.
- The egg, measuring 0.8 mm in length and shaped like a teardrop, contains a single embryo surrounded by a chorion and a protective operculum at one pole.
- The operculum remains sealed until embryogenesis is complete; at hatching, the embryo uses a specialized rotary motion to break the operculum and emerge.
Typical production rates range from 5 to 10 eggs per day, with a total clutch size of 30–50 eggs over the female’s 30‑day lifespan. Incubation lasts 7–10 days under normal scalp conditions (temperature ≈ 34 °C, relative humidity 70‑80 %). After hatching, the nymph remains attached to the hair for a brief period before dropping to the scalp to begin feeding.
Key physiological factors influencing egg formation include:
- Hormonal regulation by juvenile hormone analogs, which trigger oocyte maturation.
- Nutrient allocation from the female’s blood meals; each egg requires approximately 0.1 µL of ingested plasma.
- Environmental cues such as host movement and hair density, which affect oviposition site selection to maximize egg survival.
Understanding this reproductive mechanism clarifies why lice infestations spread quickly and why removal of attached eggs—commonly referred to as “nits”—is essential for effective control.