Head lice are parasitic insects that live exclusively on humans. They live on the head and they suck blood every 2-3 hours from their host. They like to crawl along the hair. They have claws that are especially developed to hold onto human hair shafts. They don’t live very long if they come off hair shafts. Maybe 24 to 48 hours. They start life as an egg that is laid by an adult louse on the bottom of a hair shaft. About within 1 centimeter or about a quarter of an inch near a scalp. Sometime the eggs are called nits. The nits hatch out in 7 to 11 days or so and become a nymph which is a baby louse. Very shortly thereafter they progress into an adult louse and they start the cycle all over again of breeding and laying eggs and sucking your blood.