Editing Louse (section)

==Description==
Nearly 5,000 species of louse have been identified, about 4,000 being parasitic on birds and 800 on mammals. Lice are present on every continent in all the habitats that their host animals occupy.<ref name=info/> They are found even in the [[Antarctic]], where [[penguin]]s carry 15 species of lice (in the genera ''[[Austrogonoides]]'' and ''[[Nesiotinus]]'').<ref>{{cite journal | vauthors = Banks JC, Paterson AM |title=A penguin-chewing louse (Insecta : Phthiraptera) phylogeny derived from morphology |journal=Invertebrate Systematics |date=2004 |volume=18 |issue=1 |pages=89–100 |doi=10.1071/IS03022 |s2cid=53516244 }}</ref>

<gallery mode="nolines">
File:Ricinus bombycillae (Denny, 1842).JPG|''Ricinus bombycillae'', an amblyceran louse from a [[Bohemian waxwing]]
File:Trinoton anserinum (Fabricius, 1805).JPG|''Trinoton anserinum'', an amblyceran louse from a [[mute swan]]
File:Lice image01.jpg|''[[Bovicola]] limbata'', an ischnoceran louse from [[goat]]s. The species is [[sexually dimorphic]], with the male smaller than the female.
</gallery>

Lice are divided into two groups: sucking lice, which obtain their nourishment from feeding on the [[Sebaceous gland|sebaceous secretions]] and body fluids of their host; and chewing lice, which are [[scavenger]]s, feeding on [[skin]], fragments of feathers or hair, and debris found on the host's body. Many lice are specific to a single species of host and have co-evolved with it. In some cases, they live on only 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. Lice generally cannot survive for long if removed from their host.<ref name=IIBD>{{cite book | vauthors = Hoell HV, Doyen JT, Purcell AH |year=1998 |title=Introduction to Insect Biology and Diversity |edition=2nd |publisher= [[Oxford University Press]] |pages= 407–409|isbn= 978-0-19-510033-4}}</ref> If their host dies, lice can opportunistically use [[phoresis]] to hitch a ride on a fly and attempt to find a new host.<ref>{{cite thesis | vauthors = Harbison CW | date = 2008 |title=Ecology and Evolution of Transmission in Feather-feeding Lice (Phthiraptera: Ischnocera) | degree = Doctoral  | work = Department of Biology | publisher = University of Utah |url=https://books.google.com/books?id=RUfFjqPoQTEC&pg=PA83 |isbn=978-0-549-46429-7 |pages=83–87}}</ref>

Sucking lice range in length from {{convert|0.5|to|5|mm|in|frac=64|abbr=on}}. They have narrow heads and oval, flattened bodies. They have no [[ocelli]], and their compound eyes are reduced in size or absent. Their [[Antenna (biology)|antennae]] are short with three to five segments, and their mouthparts, which are retractable into their head, are adapted for piercing and sucking.<ref name=Capinera/> There is a cibarial pump at the start of the gut; it is powered by muscles attached to the inside of the cuticle of the head. The mouthparts consist of a proboscis which is toothed, and a set of stylets arranged in a cylinder inside the proboscis, containing a salivary canal ([[ventral]]ly) and a food canal ([[dorsally]]).<ref name=GullanCranston>{{cite book| vauthors = Gullan PJ, Cranston PS |title=The Insects: An Outline of Entomology |date=2014 |publisher=Wiley |isbn=978-1-118-84615-5 |pages=41–42}}</ref> The thoracic segments are fused, the abdominal segments are separate, and there is a single large claw at the tip of each of the six legs.<ref name=Capinera>{{cite book| vauthors = Capinera JL |title=Encyclopedia of Entomology |url=https://books.google.com/books?id=i9ITMiiohVQC&pg=PA838 |year=2008 |publisher=Springer Science & Business Media |isbn=978-1-4020-6242-1 |pages=838–844}}</ref>

Chewing lice are also flattened and can be slightly larger than sucking lice, ranging in length from {{convert|0.5|to|6|mm|in|frac=64|abbr=on}}. They are similar to sucking lice in form but the head is wider than the thorax and all species have compound eyes. There are no ocelli and the mouthparts are adapted for chewing. The antennae have three to five segments and are slender in the suborder [[Ischnocera]], but club-shaped in the suborder [[Amblycera]]. The legs are short and robust, and terminated by one or two claws. Some species of chewing lice house [[symbiotic]] bacteria in [[bacteriocyte]]s in their bodies. These may assist in digestion because if the insect is deprived of them, it will die.
Lice are usually [[Crypsis|cryptically coloured]] to match the fur or feathers of the host.<ref name=Capinera/><ref>{{cite web |url=http://phthiraptera.info/classification/23 |title=Phthiraptera: Summary |vauthors=Smith V |publisher=Phthiraptera.info |access-date=25 October 2015 }}{{Dead link|date=August 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> A louse's colour varies from pale beige to dark grey; however, if feeding on blood, it may become considerably darker.

Female lice are usually more common than males, and some species are [[parthenogenetic]], with young developing from unfertilized eggs. A louse's [[egg]] is commonly called a nit. Many lice attach their eggs to their hosts' 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 [[Personal grooming|preening]], such as the interior of feather shafts. Living louse eggs tend to be pale whitish, whereas dead louse eggs are yellower.<ref name=IIBD/> Lice are [[exopterygote]]s, being born as miniature versions of the adult, known as [[nymph (biology)|nymphs]]. The young moult three times before reaching the final adult form, usually within a month after hatching.<ref name=IIBD/>

Humans host three different kinds of lice: [[head lice]], [[body lice]], and [[Crab louse|pubic lice]]. Head lice and body lice are subspecies of ''Pediculus humanus'', and pubic lice are a separate species, ''Pthirus pubis''. Lice infestations can be controlled with [[Nit comb|lice combs]], and medicated shampoos or washes.<ref>{{cite journal | vauthors = Mumcuoglu KY | title = Prevention and treatment of head lice in children | journal = Paediatric Drugs | volume = 1 | issue = 3 | pages = 211–8 | year = 1999 | pmid = 10937452 | doi = 10.2165/00128072-199901030-00005 | s2cid = 13547569 }}</ref>