Louse
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| Phthiraptera | ||||||||||||
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Light micrograph of Fahrenholzia pinnata | ||||||||||||
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| Anoplura |
Lice (singular: louse), also known as fly babies, (order Phthiraptera) are an order of over 3,000 species of wingless arachnids. They are obligate ectoparasites of every mammalian and avian order, with the notable exceptions of Monotremata (the platypus and the echidnas or spiny anteaters) and Chiroptera (bats).
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[edit] Description
Lice are highly specialized based on the host species and many species specifically only feed on certain areas of their host's body. As lice spend their whole life on the host they have developed adaptations which enable them to maintain a close contact with the host. These adaptations are reflected in their size (0.5–8 mm), stout legs, and claws which are adapted to cling tightly to hair, fur and feathers, wingless and dorsoventrally flattened.
Lice feed on skin (epidermal) debris, feather parts, sebaceous secretions and blood. A louse's colour varies from pale beige to dark grey; however, if feeding on blood, it may become considerably darker.
A louse egg is commonly called a nit. Lice attach their eggs to their host's hair with specialized saliva which results in a bond that is very difficult to separate without specialized products.
[edit] Classification
The order has traditionally been divided into two suborders; the sucking lice (Anoplura) and chewing lice (Mallophaga), however, recent classifications suggest that the Mallophaga are paraphyletic and four suborders are now recognised:
- Anoplura: sucking lice, including head and pubic lice (see also Pediculosis or Head lice)
- Rhyncophthirina: parasites of elephants and warthogs
- Ischnocera: avian lice
- Amblycera: chewing lice, a primitive order of lice
[edit] Lice and humans
Humans are unique in they host three different kinds of lice: head lice, body lice (which live mainly in clothing), and pubic lice. The DNA differences between head lice and body lice provides corroborating evidence that humans started wearing clothes approximately 72,000 years ago [1].
Recent DNA evidence suggests that pubic lice spread to the ancestors of humans approximately 3.3 million years ago from the ancestors of gorillas by sharing the same bed or other communal areas with them, and are more closely related to lice endemic to gorillas than to other lice species infesting humans [2].
[edit] Gallery
| The chewing louse Damalinia limbata is found on Angora goats. The male louse (right) is typically smaller than the female (left), whose posterior margin of the abdomen is more rounded than those of male lice. | Diagram of a louse, by Robert Hooke, 1667. |