Phthiraptera
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Fahrenholzia pinnata
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Scientific classification
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Order:
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Phthiraptera
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Lice
(singular:
louse
), are wingless
insects
that live in
hair
. They are all external
parasites
on every species of
bird
and most
mammalian
orders. They are not found on
Monotremes
and a few
eutherian
orders, namely
bats
(Chiroptera),
whales, dolphins and porpoises
(Cetacea) and
pangolins
(Pholidota). There are more than 3,000 different
species
; three are classified as human lice.
Lice spend their whole life on the host. They are adapted to keep close contact with the host. These adaptations are reflected in their size (0.5?8
mm
), stout legs, and claws which are adapted to clinging tightly to hair, fur and feathers. They are also wingless and flattened.
Lice feed on
skin
(epidermal) debris,
feather
parts,
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.
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. The process is called
nit-picking
, and is often done with a close-toothed metal comb. For humans, anti-insect shampoos are available.
The order has traditionally been divided into two suborders; the
sucking lice
(Anoplura) and
chewing lice
(Mallophaga). Four suborders are now recognised:
- Anoplura:
sucking
lice, including head and pubic lice
- Rhyncophthirina: parasites of elephants and
warthogs
- Ischnocera: avian lice
- Amblycera:
chewing
lice, a primitive order of lice
- Amblycera:
jumping
lice have very strong hind legs and can jump a distance of three feet
It has been suggested that the order is contained by the Troctomorpha suborder of
Psocoptera
. What this means is that lice may have evolved from free-living species of that group.
Humans are unique in that they host three different species 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 BCE.
[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]
-
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
The English
Wiktionary
has a dictionary definition (meanings of a word) for:
louse