Life Cycle of Head Lice

lifecycle

The life cycle of the head louse has three stages: nit, nymph, and adult. The life cycle of a single louse from egg to egg is about 1 month.

Nits: Head lice eggs are called nits. Nits are laid by the adult female louse and are attached to the base of the hair shaft by strong cement. They are located close to the scalp because they require body heat for incubation. More nit characteristics:

Size – 0.8mm by 0.3mm
Shape – Oval
Color – Yellow to white
Location – Within 6 mm of the scalp
Duration – Nits take 6 – 9 days to hatch.
Nit Picture

Nymphs: When an egg hatches, it releases a nymph. The nit shell stays attached to the hair and turns a dull yellow color. The nymph looks like an adult louse but is smaller. As the nymph grows, it molts out of its exoskeleton 3 times before it becomes an adult. More nymph characteristics:

Size – Variable but about the size of a pinhead
Shape – Same shape as the adult louse
Color – Yellow to rust-colored
Location – Close to the scalp, especially behind the ears and at the neckline
Duration – Nymphs become adults after about 7 days
Nymph Picture

Adult: The adult louse feeds about 5 times a day by piercing the skin with its claws, injecting irritating saliva, and sucking blood. Lice do not become engorged like ticks, but their color changes to a rust color after feeding. Head lice hold onto the hair with hook-like claws found at the end of each of their 6 legs. Adult lice are active and can travel quickly. More adult characteristics: