Facts About Head Lice

What are head lice?
  Head lice, or Pediculosis Humanus Capitis, are tiny crawling insects that are 2-4 mm in length and live on the human scalp. They are parasites that survive by sucking small amounts of blood from the head. Head lice cannot live more than 24 hours off their human host. They do not live on pets or other parts of the body.

Life Cycle: The louse (singular of lice) attaches its eggs, otherwise known as nits, to the base of a hair shaft. It takes 7-10 days for an egg to hatch and 9-12 days for a nymph to grow to adult size. A female louse may lie up to 10 eggs per day.
What do head lice look like?
  An adult louse is wingless, has 6 legs, and ranges in color from reddish brown to gray. Lice have claws to grasp the hair and cannot jump, hop or fly. A nit is a small yellowish-white, oval shaped egg that sits to the side of a hair shaft glued at an angle.
Below is a picture of head lice from the CDC (Center for Disease Control) web site. It shows lice in their 3 phases: egg (nit), nymph (young louse) and an adult louse.
What are the symptoms of head lice?
Tickling feeling of something moving through hair
Less common are red bite marks on the scalp and sores caused by scratching, which may become infected.