
[Middle English, from Old English lūs.]
For more information on louse, visit Britannica.com.
| levothyroxine sodium, levonorgestrel, levomepromazine | |
| licence, lidocaine, linctus |
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.
Bibliography
See bulletins of the U.S. Dept. of Agriculture.
| lounge lizard, lotta, lotsa | |
| lousy, love, love juice |
Pl. lice; a general name for various species-specific parasitic insects, the true lice, which infest mammals and belong to the order Phthiraptera. This is divided into two suborders, Mallophaga, the biting lice, and Anoplura, the sucking lice. They are grayish, wingless, dorsoventrally flattened, and vary in length from about 1.5 to 4 mm. They stimulate rubbing, scratching and restlessness, causing damage to fleece and loss of production. Heavy infestations with sucking lice may cause serious anemia. Louse infestation is also called pediculosis.
The term louse is also used loosely with respect to other external parasites, e.g. whale ‘lice’ are barnacles and small copepods.

| Phthiraptera | |
|---|---|
| Light micrograph of Fahrenholzia pinnata | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Subclass: | Pterygota |
| Infraclass: | Neoptera |
| Superorder: | Exopterygota |
| Order: | Phthiraptera Haeckel, 1896 |
| Suborders | |
Louse (plural: lice) is the common name for members of over 3,000 species of wingless insects of the order Phthiraptera; three of which are classified as human disease agents. They are obligate ectoparasites of every avian and mammalian order except for monotremes (the platypus and echidnas), bats, whales, dolphins, porpoises and pangolins.
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Most lice are scavengers, feeding on skin and other debris found on the host's body, but some species feed on sebaceous secretions and blood. Most are found only on specific types of animals, and, in some cases, only to a particular part of the body; some animals are known to host up to fifteen different species, although one to three is typical for mammals, and two to six for birds. For example, in humans, different species of louse inhabit the scalp and pubic hair. Lice generally cannot survive for long if removed from their host.[1]
A louse's color varies from pale beige to dark gray; however, if feeding on blood, it may become considerably darker. Female lice are usually more common than the males, and some species are even known to be parthenogenetic. A louse's egg is commonly called a nit. Many lice attach their eggs to their host's hair with specialized saliva; the saliva/hair bond is very difficult to sever without specialized products. Lice inhabiting birds, however, may simply leave their eggs in parts of the body inaccessible to preening, such as the interior of feather shafts. Living lice eggs tend to be pale white. Dead lice eggs are more yellow.[1]
Lice are exopterygotes, being born as miniature versions of the adult, known as nymphs. The young moult three times before reaching the final adult form, usually within a month of hatching.[1]
Lice are optimal model organisms to study the ecology of contagious pathogens since their quantities, sex-ratios etc. are easier to quantify than those of other pathogens. The ecology of avian lice has been studied more intensively than that of mammal lice.
The order has traditionally been divided into two suborders, the sucking lice (Anoplura) and the chewing lice (Mallophaga); however, recent classifications suggest that the Mallophaga are paraphyletic and four suborders are now recognized:
It has been suggested that the order is contained by the Troctomorpha suborder of Psocoptera.
Humans host three different kinds of lice: head lice, body lice, and pubic lice. Lice infestations can be controlled with lice combs, and medicated shampoos or washes. Adult and nymphal lice can survive on sheep-shearers' moccasins for up to 10 days, but microwaving the footwear for five minutes in a plastic bag will kill the lice.[17]
Lice have been the subject of significant DNA research that has led to discoveries on human evolution. For example, recent DNA evidence suggests that pubic lice spread to humans approximately 2,000,000 years ago from gorillas.[18] Additionally, the DNA differences between head lice and body lice provide corroborating evidence that humans started losing body hair, also about 2,000,000 years ago.[19]
Ricinus bombycillae, an Amblyceran louse from the bohemian waxwing
Trinoton anserinum, an Amblyceran louse from a mute swan.
Damalinia limbata is an Ischnoceran louse from goats. The male is smaller than the female.
Diagram of a louse, by Robert Hooke, 1667.
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Dansk (Danish)
n. - lus
v. tr. - afluse
Nederlands (Dutch)
luis, schoft, ontluizen
Français (French)
n. - pou, salaud (péj)
v. tr. - bousiller, foutre en l'air
Deutsch (German)
n. - Laus
v. - lausen
Ελληνική (Greek)
n. - (εντομ.) ψείρα, (καθομ.) κάθαρμα
v. - ξεψειριάζω
Português (Portuguese)
n. - piolho (m) (Entom.) (Zool.)
v. - espiolhar, limpar de piolhos
Español (Spanish)
n. - piojo
v. tr. - echar a perder
Svenska (Swedish)
n. - lus, (sl.) äckel, fjant
v. - avlusa
中文(简体)(Chinese (Simplified))
虱子, 寄生虫, 清除, 损坏, 搞糟
中文(繁體)(Chinese (Traditional))
n. - 蝨子, 寄生蟲
v. tr. - 清除, 損壞, 搞糟
한국어 (Korean)
n. - 쥐들, 비열한 놈, 이
v. tr. - 이를 없애다
日本語 (Japanese)
n. - シラミ, ハジラミ, 寄生虫
العربيه (Arabic)
(الاسم) قمله (فعل) يفلي القمل
עברית (Hebrew)
n. - אדם שפל, כינה
v. tr. - בילבל, סיבך, קילקל, פלה כינים
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