Lice are ectoparasites that live on the human body. They are wingless and have six legs on which are attached strong claws that they use to grasp on tightly to hair shafts or clothing fibres. With their piercing mouthparts they puncture the skin to feed on human blood. They also inject a saliva which causes itching. Lice can survive for up to 10 days without feeding if they become detached from their human host.
Head lice, the most common infestation in humans, are colloquially known as cooties and their eggs are called nits. Pubic lice are smaller than the other two species, and have a short body resembling a crab — hence the common name for pubic lice, 'crabs'.