Life Cycle of Head Lice

by Tracey on May 8, 2009


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:

  • Size – The size of a pinhead. The female louse is larger than the male.
  • Shape – Oval with 3 legs and claws at the end of each leg
  • Color – Rust
  • Location – Close to the scalp, especially behind the ears and at the neckline
  • Duration – Adult lice can live up to 30 days on a person’s head
  • Reproduction – An adult female can lay up to 8 nits per day
  • Adult Louse Picture

For Natural Headlice Help check us out here

Heather Brannon, MD,

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