Human Lice

Human Lice Anoplurans are parasitic arthropods. They are commonly referred to as "sucking" lice. Lice are highly host specific and many species prefer specific sites on their host's body. They can not survive without a host; therefore, lice have developed many adaptations that help them stay in close contact with their host. There are three types of human lice: The head louse (Pediculus humanus capitas), the body louse (Pediculus humanus humanus), and the crab louse (Pthirus pubis). Anoplurans are wingless insects. Each leg is equipped with a single claw. Lice usually use their claw to grab and hold onto hair shafts. Their abdomens are distinctly longer than wide. Their thoracic segments are fused and their tarsi is uni-segmented. Lice have 6 pairs of breathing spiracles. Their body color depends on the color of their host's hair. Anoplurans have reduced compound eyes and no ocelli. Their segmented antennas are short. Their mouth parts are designed for piercing. The ventral stylet is the main penetration organ. When the louse is done sucking it will retract the entire proboscis into its head. A female louse can lay 50 to 150 eggs per day. Louse eggs are usually called nits. Nits are found on the scalp, behind the ears, and on the base of the neck. They are usually oval- or tear-shaped. Live eggs are tan in color and dead eggs are grayish-white. Female lice usually glue their eggs onto the side of the hair shaft. Most eggs hatch within 5 to 10 days, depending on environmental conditions. There are three nymphal stages; therefore, the life cycle takes place every 18 days. An adult male usually lives for 10 days and an adult female can live up to 25 days. All lice feed on blood; therefore, they must feed every 3 to 6 hours. Lice can survive without a blood meal for about 48 hours. Head lice and body lice are morphologically indistinguishable, although head lice are smaller than body lice (the head louse is about 3