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louse, common name for members of either of two distinct orders of wingless, parasitic, disease-carrying insects. 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 rickettsia) and bacterial infections such as relapsing fever; 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 metamorphosis 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 aphid is sometimes called plant louse.

Lice are classified in the phylum Arthropoda, class Insecta, orders Anoplura and Mallophaga.


See bulletins of the U.S. Dept. of Agriculture.

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(invertebrate zoology)
The common name for the apterous ectoparasites composing the orders Anoplura and Mallophaga.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


1. any wingless bloodsucking insect of the order Anoplura: includes Pediculus capitis (head louse), Pediculus corporis (body louse), and the crab louse, all of which infest man
2. biting or bird louse any wingless insect of the order Mallophaga, such as the chicken louse: external parasites of birds and mammals with biting mouthparts
3. any of various similar but unrelated insects, such as the plant louse and book louse
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
References in periodicals archive ?
Thus the comb data indicated these prehistoric Arica populations created functional objects for delousing and grooming.
The blueprints give chilling details, with gas chambers, crematoria, delousing facilities and watchtowers drawn to scale.
Through the metaphor of Jews as "pests," the SS then fused these two applications, on a monumental scale, in "the gas chamber and crematorium industry in Auschwitz and other concentration camps." At every turn, according to Sloterdijk, product design was there to assist in new forms of environmental terror: For example, without the breakthrough of Zyklon B, a solid form of hydrogen cyanide that allows for its transportation before its conversion to gas, the technology of delousing might not have found its way quite so readily into the Nazi camps.
Reality also emerges by means of archival material: Luis Cernuda, the British documentary about Owen's utopian experience, engineers on the way to work, although they are not going to the Humanisphere, as the voice-over says, or the delousing campaigns during the war.
Friends in the goat world and Drummond's book helped us through the processes of worming, tetanus shot administration, hoof trimming and delousing. (Angoras can get species-specific lice that must be controlled.) Randy developed a fencing obsession, partly out of necessity, as he tried out different types of fencing, posts and fasteners to keep our boys in.
Look for a crusty circle on the face or neck of your goats when you are doing your spring delousing.
Sometimes visitors were required to undergo delousing. Later the government set up a clinic and small hospital, and then an eighty-bed typhus hospital and other sanitary facilities for the leadership.
Indeed, well into the 17th century, artists depicted wealthy women apparently proudly delousing their children, much as monkeys pick their progeny's nits--perhaps a skill worth cultivating again in this era of resurgent lice and bedbugs.
customs agents began a system of delousing Mexicans by spraying them with insecticides, gasoline, kerosene, and cyanide-based pesticides before they crossed the Santa Fe bridge in Texas to work in the U.S.
She concludes with the "delousing" process, including dealing with overload and picking the victims for layoffs.
Additional secondary missions for these companies included supporting the theater Chemical officer with dry-cleaning, waterproofing, dyeing (often with camouflage patterns), fireproofing, mildew proofing, mothproofing (wool was used extensively in military clothing during World War II), insect repellent treatment, delousing, and sterilizing.
In Europe it was commonly used as a powdered delousing agent.