If you have young children, it's highly likely that at some point you will be sharing your home with lice. Best to know your enemy. From KQED:
Head lice can move only by crawling on hair. They glue their eggs to individual strands, nice and close to the scalp, where the heat helps them hatch. They feed on blood several times a day. And even though head lice can spread by laying their eggs in sports helmets and baseball caps, the main way they get around is by simply crawling from one head to another using scythe-shaped claws.
These claws, which are big relative to a louse's body, work in unison with a small and spiky thumblike part called a spine. With the claw and spine at the end of each of its six legs, a louse grasps a hair strand to hold on tightly, or quickly crawl from hair to hair like a speedy acrobat.