They belong to a family of insects called biting lice, which also include head lice. Crabs are referred to as ectoparasites because they live on the outer surface of the body, such as in pubic hair and occasionally in the hair of the chest, armpits, eyelashes and eyebrows.
Crab lice thrive in warm conditions.
They nourish themselves by drinking the blood of their host. Their life-span is about one month but they lay many eggs which reproduce several generations before they die. Without a human host, they only survive for about 24 hours. However, they may deposit eggs that can take up to 7 days to hatch in bedding or towels. Once hatched, a crab louse will make its way onto the pubic hair and lay eggs.