Sucking
lice are irritating little pests that feed on the blood of their host.
They attack humans and animals and their bites are often very irritating.
Each species usually attacks one or a few related species of hosts, and
generally lives on a particular part of the host's body. Eggs are
usually attached to hair of the host; egg of the body louse are laid on
clothing. Sucking lice spend their life on their host and do not survive
long away from it.. They are small, usually less than 4mm in length, flattened and wingless. Of course their mouth parts are made for sucking and they withdraw into the head when not in use. The antennae are short, threadlike or tapering distally, 3 to 5 segmented. The head is small and nearly always narrower than the thorax.
There are two subspecies of the common human louse: Pediculus humanus capitis, the head louse, and P. humanus humanus, the body louse, or cootie. The body louse is an important carrier of epidemic typhus; other louse-borne human diseases are trench fever and relapsing fever.
Information provided by: http://www.arthropod.net