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 Light micrograph of Fahrenholzia pinnata
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Lice (singular: louse), (order Phthiraptera), are an order of over 3,000 species of wingless insects; three of which are classified as human disease agents. They are obligate ectoparasites of every avian and most mammalian orders. They are not found on Monotremes (the platypus and the echidnas or spiny anteaters) and a few eutherian orders, namely the bats (Chiroptera), whales, dolphins and porpoises (Cetacea) and pangolins (Pholidota).
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Description
As lice spend their entire lives on the host, they have developed adaptations which enable them to maintain 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, and that they are wingless and dorsoventrally flattened.
Lice feed on skin (epidermal), sebaceous secretions and blood. A louse's color varies from pale beige to dark grey; however, if feeding on blood, it may become considerably darker. They mostly like clean hair.
A louse's 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. Living lice eggs tend to be pale white. Dead lice eggs are more yellow. Lice are very annoying and are difficult to remove, but not impossible. Lice infestations can be controlled with lice combs, and medicated shampoos or washes.
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
It has been suggestedweasel words that the order is contained by the Troctomorpha suborder of Psocoptera. Lice can not jump or fly.
Lice and humans
Humans are unique in that 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 provide corroborating evidence that humans started wearing clothes at approximately 70,000 BC..[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]
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. |
 Trichodectes canis, the biting dog louse |
References
- ^ John Travis (2003-08-23). The naked truth? Lice hint at a recent origin of clothing (dead link – Scholar search) 164 (8): 118. Science News.
- ^ David L Reed, Jessica E Light, Julie M Allen and Jeremy J Kirchman (2007). Pair of lice lost or parasites regained: the evolutionary history of anthropoid primate lice. BMC Biology 5: 7. doi:.
See also
External links
- Lice Pest Control Information - National Pesticide Information Center
- Bed-hopping led humans to 3 million-year itch
- www.phthiraptera.org has extensive scientific information.
- body and head lice on the UF / IFAS Featured Creatures Web site
- crab louse on the UF / IFAS Featured Creatures Web site
- WebMD Lice Info
- Lice chapter in EPA and UF / IFAS National Public Health Pesticide Applicator Training Manual
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Wikipedia content modification information:
- This page was last modified on 10 October 2008, at 20:42.
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