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louse,common name for members of either of two distinct orders of wingless, parasitic, disease-carrying insectsinsect,
invertebrate animal of the class Insecta of the phylum Arthropoda. Like other arthropods, an insect has a hard outer covering, or exoskeleton, a segmented body, and jointed legs. Adult insects typically have wings and are the only flying invertebrates.
..... Click the link for more information. . Lice of both groups are small and flattened with short legs adapted for clinging to the host.
The sucking lice, of the order Anoplura, are external parasites of humans and other mammals, feeding on blood by means of their piercing-and-sucking mouthparts. The group includes the body lice and head lice, considered varieties of the same species, Pediculus humanus, and the crab, or pubic, louse, Phthirus pubis, named for its crablike appearance. A female sucking louse lays about 300 eggs, or nits, in her lifetime, cementing them to body hairs and underclothing. The larva resembles the adult; the life cycle takes about 16 days. Sucking lice infestations are common in crowded living conditions and where clothing is not changed or washed frequently. Body lice may transmit rickettsial diseases (see rickettsiarickettsia
, any of an order (Rickettsiales) of very small microorganisms, many disease-causing, that live in vertebrates and are transmitted by bloodsucking parasitic arthropods such as fleas, lice (see louse), and ticks.
..... Click the link for more information. ) and bacterial infections such as relapsing feverrelapsing fever,
infectious disease caused by a spirochete bacteria of the genus Borrelia and characterized by a high fever that breaks and then recurs a one to two weeks later. Relapsing fever may be transmitted by body lice or soft ticks.
..... Click the link for more information. ; infection results from scratching the crushed louse or its feces into the skin.
The chewing, or biting, lice, of the order Mallophaga, have chewing mouthparts and feed on hair, skin, or feather fragments of the host. They attack birds, rodents, and domesticated animals. Although they do not actually puncture the skin, and thus are scavengers and not true parasites, they often multiply so rapidly that they irritate, weaken, and may even kill the host. The chicken louse, Menopon pallidum, if left uncontrolled, can be a major problem in poultry production. Chewing lice may produce 6 to 12 generations annually. The eggs hatch into rapidly developing young in which metamorphosismetamorphosis
[Gr.,=transformation], in zoology, term used to describe a form of development from egg to adult in which there is a series of distinct stages. Many insects, amphibians, mollusks, crustaceans, and fishes undergo metamorphosis, which may involve a change in habitat,
..... Click the link for more information. is incomplete, as in many parasites.
The book louse is a tiny, wingless, cosmopolitan insect that damages books by feeding on glue, paste, and paper. It resembles lice but is not related, belonging to the order Psocoptera. The aphidaphid
or plant louse,
tiny, usually green, soft-bodied, pear-shaped insect injurious to vegetation. It is also called greenfly and blight. Aphids are mostly under 1-4 in. (6 mm) long.
..... Click the link for more information. is sometimes called plant louse.
Lice are classified in the phylum ArthropodaArthropoda
[Gr.,=jointed feet], largest and most diverse animal phylum. The arthropods include crustaceans, insects, centipedes, millipedes, spiders, scorpions, and the extinct trilobites.
..... Click the link for more information. , class Insecta, orders Anoplura and Mallophaga.
See bulletins of the U.S. Dept. of Agriculture.