Body lice are small, parasitic insects found mainly on the clothing of infested people, and occasionally on their bodies or bedding. Although they are related to head lice, and look almost exactly the same, body lice rarely infest the head hair. Instead, they spend most of their life on an infested person's clothing, crawling onto the skin to feed on the host's blood one or more times a day.
Female lice glue their eggs on the seams of clothing worn near the skin, where body heat allows them to hatch in about a week. A female louse can produce 300 or more eggs in her adult life, at a rate of about 10 per day. Eggs require temperatures between 75° and 100° Fahrenheit to hatch. Hatchlings develop to the adult stage in about nine days if they remain close to the host, but this can take as long as four weeks if the person takes the clothing off.
Most body lice are on homeless or destitute adults who rarely change their clothes. Children rarely have body lice.