Any of more than 400 species (suborder Anoplura, order Phthiraptera) of small, wingless, flat ectoparasitic insects found worldwide.
They have piercing and sucking mouthparts for extracting their food of mammals' blood and tissue fluids. The nymphs mature after several molts. Species are host-specific: Pediculus infests humans (see human louse ), whereas other sucking lice (genera Haematopinus and Linognathus ) attack domestic animals, such as hogs, cattle, horses, and dogs.