Editing Louse (section)

{{Short description|Infraorder of insects}}
{{Redirect|Lice|the infection|Pediculosis|the district of Diyarbakır Province in Turkey|Lice, Turkey|the episode of The Office|Lice (The Office)|other uses|Louse (disambiguation)}}
{{pp-vandalism|small=yes}}
{{Good article}}
{{Use British English|date=November 2015}}
{{Automatic taxobox
| name = Phthiraptera
| fossil_range = {{fossilrange|Cenomanian|present|earliest=Cretaceous}}
| image = Fahrenholzia pinnata.JPG
| image_caption = [[Light micrograph]] of ''[[Fahrenholzia pinnata]]''
| taxon = Phthiraptera
| authority = [[Haeckel]], 1896
| display_parents = 2
| subdivision_ranks = Parvorders
| subdivision =
*[[Amblycera]]
*[[Anoplura]]
*[[Rhynchophthirina]]
*[[Ischnocera]]
*[[Trichodectera]]?
| subdivision_ref = <ref name="deMoya2021"/>
}}

'''Louse''' ({{plural form}}: '''lice''') is the common name for any member of the [[infraorder]] '''Phthiraptera''', which contains nearly 5,000 species of wingless [[parasitic]] [[insect]]s. Phthiraptera was previously recognized as an [[order (biology)|order]], until a 2021 genetic study determined that they are a highly modified lineage of the order [[Psocodea]], whose members are commonly known as booklice, barklice or barkflies.

Lice are [[obligate parasite]]s, living externally on warm-blooded [[Host (biology)|hosts]], which include every species of [[bird]] and [[mammal]], except for [[monotreme]]s, [[pangolin]]s, and [[bat]]s. Chewing lice live among the hairs or feathers of their host and feed on skin and debris, whereas sucking lice pierce the host's skin and feed on blood and other secretions. They usually spend their whole life on a single host, cementing their eggs, called [[Head louse#Eggs/Nits|nits]], to hairs or feathers. The eggs hatch into [[Nymph (biology)|nymphs]], which moult three times before becoming fully grown, a process that takes about four weeks.

Humans host two species of louse—the [[head louse]] and the [[body louse]] are subspecies of ''[[Pediculus humanus]]''; and the [[pubic louse]], ''[[Pthirus]] pubis''. Lice are [[Vector (epidemiology)|vectors]] of diseases such as [[typhus]]. Lice were ubiquitous in human society until at least the [[Middle Ages]]. They appear in folktales, songs such as ''The Kilkenny Louse House'', and novels such as [[James Joyce]]'s ''[[Finnegans Wake]]''.

The body louse has the smallest [[genome]] of any known insect; it has been used as a [[model organism]] and has been the subject of much research.  They commonly feature in the psychiatric disorder [[delusional parasitosis]]. A louse was one of the early subjects of [[Microscope|microscopy]], appearing in [[Robert Hooke]]'s 1667 book, ''[[Micrographia]]''. 

The oldest known fossil lice are from the [[Cretaceous]].<ref name=Archimenopon>{{Cite journal|last1=Zhang |first1=Y. |last2=Rasnitsyn |first2=A. P. |last3=Zhang |first3=W. |last4=Song |first4=F. |last5=Shih |first5=C. |last6=Ren |first6=D. |last7=Wang |first7=Y. |last8=Li |first8=H. |last9=Gao |first9=T. |year=2024 |title=Stem chewing lice on Cretaceous feathers preserved in amber |journal=Current Biology |volume=34 |issue=4 |pages=916–922.e1 |doi=10.1016/j.cub.2024.01.027 |pmid=38320551 |bibcode=2024CBio...34E.916Z }}</ref>