What are head lice?

Head Lice (Pediculus humanus capitis) are a common parasite found in human hair. About 1/16 to 1/8 inch long, they are small, wingless, grayish-white insects with flattened, elongated bodies, somewhat oval heads and sharp little claws perfectly evolved for what they do best—crawling along and clinging tenaciously to shafts of hair in between meals.

Infestations of head lice are generally accompanied by an intense itching of the scalp caused by the way they feed. Utilizing specially adapted mouthparts to cut through the skin, they literally "saw" through the scalp until they penetrate and rupture a blood vessel, whereupon they suck up blood until full.