Fleas are small (1/16 to 1/8-inch long), agile, usually dark colored, wingless insects with tube-like mouthparts adapted to feeding on the blood of their hosts. Their bodies are laterally compressed, permitting easy movement through the hairs or feathers on the host's body (or in the case of humans, under clothes). Their legs are long, the hind pair well adapted for jumping. The flea body is hard, polished, and covered with many hairs and short spines directed backward, which also assists its movements on the host.