Louse

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Most lice belong to the diverse family Philopteridae. Some species have wings and others do not. They are pale in color. They are 1/32 to 1/8-inch long. Eyes or eye tubercles (rounded areas) are present. There are 6 strong short legs with special claws at the ends for gripping. The specialized mouthparts are adapted for sucking blood.

Human lice belong to the Order Phthiraptera and family Pediculidae. The 2 subspecies of human lice—head lice and body lice-are almost identical in appearance. They are gray in color and flattened in shape. The female is about 1/16 to 1/8-inch long; the male is a little smaller. Each of the six legs has a hook-like claw to help anchor the louse to the hair shaft. Head lice do not jump or fly. Head lice tend to take on the hair color of the host.

Chewing Lice have small, flattened bodies without wings Their mouthparts have mandibles (jaws) for chewing. They have short, segmented antennae. The head is wider than the thorax. There are 1 or 2 claws on the legs. Mammal Chewing Lice are 1/32 to 1/8-inch long. They are pale brown in color. The large, square head has short antennae and mandibles for chewing. Each of the 6 short legs has a single tarsal claw.

Barklice belong to the Order Psocoptera. They have a large head, bulging eyes, and long filiform (threadlike) antennae. There are usually 2 pairs of membranous wings. They are 1/32 to 1/4-inch long. They are dull brown, black, or gray in color. Their wings are held in “rooflike” fashion and may have spots and irregular patches of color.

Booklice also belong to the Order Psocoptera. They have flat, yellowish-brown bodies and most have no wings. They are 1/64 to 1/32-inch long. They have small eyes and usually have short antennae.

Parasitic Lice have flattened, wingless bodies. Short legs are often modified for clinging to fur or feathers.

Birdlice are 1/32 to 1/4-inch long with an oval abdomen and 6 short, stout legs with 2 claws each. The large, roughly triangular head has biting mandibles.

Sucking Lice are small and have a flattened body with no wings. They are about 1/8-inch in length. Sucking mouthparts are stored inside the head when not in use. Compound eyes are small or absent.

Lice occur worldwide and live in a wide range of habitats. Some live in the soil; others in treetops. They invade buildings and houses where food is available.

Barklice are found on leaves, foliage, bark, and bare wood of standing dead trees. They are found in bird nests and on rocks where lichen grows.

Pediculus humanus live on human hosts and sometimes on monkeys. Pediculus schaeffi is found exclusively on apes. The Body Louse lives and reproduces in clothing fibers. The Head Louse lives entirely in hair. Its eggs are called nits and they are glued to the host’s hair.

Pubic Lice live almost anywhere on a very hairy body, but they are usually found in armpits, beards, and groin.

Mammal Chewing Lice live on livestock, such as horses and cattle, and on household pets. They are found on non-domesticated species as well.

Marine animals, such as seals, sea lions, and walruses, are hosts for Spiny Sucking Lice.

Lice usually feed on a specific host. For instance, Mammal Chewing Lice feed on mammals such as horses, cows, dogs, and cats. Some species, such as Barklice feed on a variety of organic matter such as lichens, fungi, and tree bark. Booklice graze in “herds” on lichen. They also eat grain, household food, and books. Sucking Lice feed on the host’s blood.

Bird Lice are a large group of pests with 2 important species. One species feeds on feathers of water birds and birds of prey. Another species attacks hummingbirds and sparrows.

The very small size of lice makes them inconspicuous and hides them from sight. Head lice camouflage themselves by taking on the color of the hair. Adult female barklice protect their eggs by covering them with silk made in their salivary glands. They also make silk tents to protect other barklice.

Lice undergo incomplete metamorphosis–egg, nymph, and adult. Eggs are attached or glued onto areas of hosts where lice live. There are usually 5 nymphal stages. A few species bear live young, but most lay eggs. Females lay 50-300 eggs at one time. There is an 8-day gestation period. Eggs can hatch any time during the year. After hatching, nymphs start feeding within minutes in order to survive. They become full adults in 9-12 days, living only about 2 weeks.

Most species are solitary, but some are sociable. Many species of lice are ectoparasites, living permanently on the bodies of birds and mammals without killing them. Some lice live in strange places, such as inside pelican pouches or in feather quills. Lice have even been found on prehistoric mummies.

Lice infestations generally occur in people who live in crowded conditions and who rarely wash their clothes. Infestation with lice is called Pediculosis. In people it causes itching and sleeplessness.

Body Lice are dangerous because they can transmit the organisms that cause infections, such as typhus, trench fever, and relapsing fever. A louse becomes a carrier after biting a patient. The infection is passed on when another individual scratches the louse or its feces into the skin. In World War I many soldiers died of these diseases.

Head Lice outbreaks are common among young children. Head Lice are transmitted from one person to another on combs, hair brushes, or hats. There are usually only 10 at a time on a head. They do not burrow into the scalp and rarely cause serious infections.

Several lice species are important pests of domestic animals, especially poultry. Dog Lice infestation may cause an animal to become very thin because constant grooming interferes with eating.

Some Bird Lice species, such as the Shaft Louse, can be serious poultry pests. Infestations of Chicken Body Lice can lead to feather-loss and infection.