"They're huge, the lice on that god-awful cliff."
Head Lice
Public DomainHead Lice - Credit: CDC/ Dr. Dennis D. Juranek

Lice are parasitic, wingless insects. 3,000 different species have been identified to date. Three of them are classified as human disease agents: head lice, body lice, and pubic lice. These can be killed and treated through use of combs, shampoo, and medical preparations.