Chewing and Sucking Lice: Phthiraptera

Lice are small, flattened, wingless insects measuring 0.01 to 0.4 inches (0.3 to 11 millimeters) in length. Females are typically larger than males. Many species are pale whitish or yellowish, while other species are brown or black. Some species have color patterns that help them to blend in with the fur or feathers of the animal on which they live. Their heads are broad and blunt to narrow with a snout. They have short antennae (an-TEH-nee), or sense organs, with only three to five segments, and no simple eyes. Compound eyes, eyes with multiple lenses, are either very small or absent. The mouthparts are directed forward. Chewing lice have well-developed jaws that either open from side to side or up and down. In most sucking lice the jaws are entirely absent, although some species have greatly reduced jaws inside their heads. The abdomen has eight to ten segments, depending on the species.

The flattened bodies are perfect for moving in the narrow spaces between feathers and fur, and the short, strong legs have one or two claws that help them to cling. The legs of most sucking lice have a single claw that clamps onto hair shafts. This reduces their chances of being removed when the animal cleans and grooms itself.