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’ve got claws that have been especially developed to hold onto human hair shafts and they don’t live very long if they come off hair shafts, maybe 24-48 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 off the scalp. Sometimes called the eggs are called nits because the louse secretes a glue type substance when she lays the egg. The nits hatch in 6-8 days or so and become a nypth which is a baby lice and very shortly thereafter they progress into an adult lice and they start the cycle all over again of sucking and feeding off your blood.