Editing Ant (section)

==Morphology==
[[Image:Scheme ant worker anatomy-en.svg|thumb|450px|left|Diagram of a worker ant (''[[Neoponera verenae]]'')]]

Ants are distinct in their [[morphology (biology)|morphology]] from other insects in having geniculate (elbowed) [[Antenna (biology)|antenna]]e, [[metapleural gland]]s, and a strong constriction of their second [[Abdomen|abdominal]] segment into a node-like [[petiole (insect anatomy)|petiole]]. The body is divided into three distinct sections (formally known as ''[[tagma (biology)|tagmata]]''): the head, [[mesosoma]], and [[metasoma]]. The petiole forms a narrow waist between their mesosoma ([[Thorax (insect anatomy)|thorax]] plus the first abdominal segment, which is fused to it) and [[gaster (insect anatomy)|gaster]] (abdomen less the abdominal segments in the petiole). The [[Petiole (insect anatomy)|petiole]] may be formed by one or two nodes (the second alone, or the second and third abdominal segments).<ref>Borror, Triplehorn & Delong (1989), p. 737</ref> Tergosternal fusion, when the tergite and sternite of a segment fuse together, can occur partly or fully on the second, third and fourth abdominal segment and is used in identification. Fourth abdominal tergosternal fusion was formerly used as character that defined the poneromorph subfamilies, Ponerinae and relatives within their clade, but this is no longer considered a [[synapomorphic]] character.<ref>{{Cite journal |last1=Ouellette |first1=Gary D. |last2=Fisher |first2=Brian L. |last3=Girman |first3=Derek J. |date=2006 |title=Molecular systematics of basal subfamilies of ants using 28S rRNA (Hymenoptera: Formicidae) |url=https://www.sciencedirect.com/science/article/pii/S105579030600100X |journal=Molecular Phylogenetics and Evolution|volume=40 |issue=2 |pages=359–369 |doi=10.1016/j.ympev.2006.03.017 |pmid=16630727 |bibcode=2006MolPE..40..359O |hdl=10211.1/1549 |issn=1055-7903|hdl-access=free }}</ref>

Like other arthropods, ants have an [[exoskeleton]], an external covering that provides a protective casing around the body and a point of attachment for muscles, in contrast to the internal skeletons of humans and other [[vertebrate]]s. Insects do not have [[lung]]s; [[oxygen]] and other gases, such as [[carbon dioxide]], pass through their exoskeleton via tiny valves called [[Spiracle (arthropods)|spiracle]]s. Insects also lack closed [[blood vessel]]s; instead, they have a long, thin, perforated tube along the top of the body (called the "dorsal aorta") that functions like a heart, and pumps [[haemolymph]] toward the head, thus driving the circulation of the internal fluids. The [[nervous system]] consists of a [[ventral nerve cord]] that runs the length of the body, with several [[ganglia]] and branches along the way reaching into the extremities of the appendages.<ref name="insectmorph">Borror, Triplehorn & Delong (1989), pp. 24–71</ref>

===Head===
[[File:Bullant head detail.jpg|thumb|[[Bull ant]] showing the powerful [[Mandible (insect mouthpart)|mandibles]] and the relatively large [[compound eye]]s that provide excellent vision]]

An ant's head contains many [[sensory organs]]. Like most insects, ants have [[compound eye]]s made from numerous tiny lenses attached together. Ant eyes are good for acute movement detection, but do not offer a high [[Optical resolution|resolution]] image. They also have three small [[ocellus|ocelli]] (simple eyes) on the top of the head that detect light levels and [[polarization (waves)|polarization]].<ref>{{cite journal | vauthors = Fent K, Wehner R | title = Oceili: a celestial compass in the desert ant cataglyphis | journal = Science | volume = 228 | issue = 4696 | pages = 192–194 | date = April 1985 | pmid = 17779641 | doi = 10.1126/science.228.4696.192 | s2cid = 33242108 | bibcode = 1985Sci...228..192F }}</ref> Compared to [[vertebrate]]s, ants tend to have blurrier eyesight, particularly in smaller species,<ref>{{cite journal | vauthors = Palavalli-Nettimi R, Narendra A | title = Miniaturisation decreases visual navigational competence in ants | journal = The Journal of Experimental Biology | volume = 221 | issue = Pt 7 | page = jeb177238 | date = April 2018 | pmid = 29487158 | doi = 10.1242/jeb.177238 | doi-access = free }}</ref> and a few [[Subterranea (geography)|subterranean]] taxa are completely [[Blindness|blind]].<ref name=Ward /> However, some ants, such as Australia's [[Myrmecia (ant)|bulldog ant]], have excellent vision and are capable of discriminating the distance and size of objects moving nearly a [[Metre|meter]] away.<ref>{{cite journal|journal= Journal of Experimental Biology|volume=119| pages=115–131| year=1985| title=Attack behaviour and distance perception in the Australian bulldog ant ''Myrmecia nigriceps''| vauthors = Eriksson ES |url= http://jeb.biologists.org/content/119/1/115.full.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://jeb.biologists.org/content/119/1/115.full.pdf |archive-date=2022-10-09 |url-status=live | issue=1|doi=10.1242/jeb.119.1.115| doi-access=free|bibcode=1985JExpB.119..115E }}</ref> Based on experiments conducted to test their ability to differentiate between selected wavelengths of light, some ant species such as ''Camponotus blandus, Solenopsis invicta,'' and ''Formica cunicularia'' are thought to possess a degree of colour vision.<ref>{{Cite journal |last1=Yilmaz |first1=Ayse |last2=Spaethe |first2=Johannes |date=2022 |title=Colour vision in ants (Formicidae, Hymenoptera) |journal= Philosophical Transactions of the Royal Society B: Biological Sciences|volume=377 |issue=1862 |doi=10.1098/rstb.2021.0291 |issn=0962-8436 |pmc=9441231 |pmid=36058251}}</ref>

Two [[antenna (biology)|antennae]] ("feelers") are attached to the head; these organs detect chemicals, [[air current]]s, and [[vibration]]s; they also are used to transmit and receive signals through touch. The head has two strong jaws, the [[Mandible (insect)|mandibles]], used to carry food, manipulate objects, construct nests, and for defence.<ref name="insectmorph"/> In some species, a small pocket (infrabuccal chamber) inside the mouth stores food, so it may be passed to other ants or their larvae.<ref>{{cite journal |vauthors=Eisner T, Happ GM | title=The infrabuccal pocket of a formicine ant: a social filtration device | journal=Psyche: A Journal of Entomology | volume=69 | pages=107–116 | year=1962 | doi=10.1155/1962/25068 | issue=3| doi-access=free }}</ref>

===Mesosoma===
Both the [[arthropod leg|legs]] and [[insect wing|wings]] of the ant are attached to the [[mesosoma]] ("thorax"). The legs terminate in a hooked [[Chelae|claw]] which allows them to hook on and climb surfaces.<ref>{{cite web|author=Holbrook, Tate|title=Ask a Biologist: Face to Face with Ants|date=22 September 2009|publisher=ASU School of Life Sciences|url=https://askabiologist.asu.edu/explore/ant-anatomy|access-date=2018-01-23}}</ref> Only reproductive ants ([[Queen (insect)|queens]] and males) have wings. Queens shed their wings after the [[nuptial flight]], leaving visible stubs, a distinguishing feature of queens. In a few species, wingless queens ([[ergatoid]]s) and males occur.<ref name="insectmorph"/>

===Metasoma===
The [[metasoma]] (the "abdomen") of the ant houses important internal organs, including those of the reproductive, respiratory (tracheae), and excretory systems. Workers of many species have their [[ovipositor|egg-laying structures]] modified into [[stinger (organ)|stings]] that are used for subduing [[predation|prey]] and defending their nests.<ref name="insectmorph"/>

===Polymorphism===
[[Image:Atta.cephalotes.gamut.selection.jpg|thumb|right|Seven [[leafcutter ant]] workers of various castes (left) and two queens (right)]]

In the colonies of a few ant species, there are physical castes—workers in distinct size-classes, called minor (micrergates), median, and major ergates (macrergates). Often, the larger ants have disproportionately larger heads, and correspondingly stronger [[mandible (insect)|mandibles]]. Although formally known as dinergates, such individuals are sometimes called "soldier" ants because their stronger mandibles make them more effective in fighting, although they still are workers and their "duties" typically do not vary greatly from the minor or median workers.<ref name=":1" /> In a few species, the median workers are absent, creating a sharp divide between the minors and majors.<ref>{{cite journal | vauthors = Wilson EO | title = The origin and evolution of polymorphism in ants | journal = The Quarterly Review of Biology | volume = 28 | issue = 2 | pages = 136–156 | date = June 1953 | pmid = 13074471 | doi = 10.1086/399512 | s2cid = 4560071 }}</ref> [[Weaver ant]]s, for example, have a distinct [[bimodal]] size distribution.<ref>{{cite journal|author=Weber, NA|year=1946|title=Dimorphism in the African ''Oecophylla'' worker and an anomaly (Hym.: Formicidae)|journal=Annals of the Entomological Society of America|volume=39|pages=7–10| url=http://antbase.org/ants/publications/10434/10434.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://antbase.org/ants/publications/10434/10434.pdf |archive-date=2022-10-09 |url-status=live|doi=10.1093/aesa/39.1.7}}</ref><ref>{{cite journal | first1 = Edward O. | last1 = Wilson | first2 = Robert W. | last2 = Taylor | name-list-style=vanc|year=1964|title=A Fossil Ant Colony: New Evidence of Social Antiquity |journal=Psyche: A Journal of Entomology|volume=71|pages=93–103|url=http://psyche.entclub.org/pdf/71/71-093.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://psyche.entclub.org/pdf/71/71-093.pdf |archive-date=2022-10-09 |url-status=live |doi=10.1155/1964/17612 |issue=2|doi-access=free }}</ref> Some other species show continuous variation in the size of workers. The smallest and largest workers in ''[[Carebara diversa]]'' show nearly a 500-fold difference in their dry weights.<ref>{{cite journal |vauthors=Moffett MW, Tobin JE |year=1991 |title=Physical castes in ant workers: a problem for ''Daceton armigerum'' and other ants |journal=Psyche: A Journal of Entomology |volume=98 |pages=283–292 |url=http://psyche2.entclub.org/articles/98/98-283.pdf |archive-url=https://web.archive.org/web/20080227015919/http://psyche2.entclub.org/articles/98/98-283.pdf |archive-date=2008-02-27 |doi=10.1155/1991/30265 |issue=4|doi-access=free }}</ref>

Workers cannot mate; however, because of the [[haplodiploid sex-determination system]] in ants, workers of a number of species can lay unfertilised eggs that become fully fertile, haploid males. The role of workers may change with their age and in some species, such as [[honeypot ants]], young workers are fed until their gasters are distended, and act as living food storage vessels. These food storage workers are called ''repletes''.<ref>{{cite journal|author=Børgesen LW |year=2000 |title=Nutritional function of replete workers in the pharaoh's ant, ''Monomorium pharaonis'' (L.)|journal=Insectes Sociaux |volume=47 |issue=2 |pages=141–146 |doi=10.1007/PL00001692|s2cid=31953751 }}</ref> For instance, these replete workers develop in the North American honeypot ant ''[[Myrmecocystus mexicanus]]''. Usually the largest workers in the colony develop into repletes; and, if repletes are removed from the colony, other workers become repletes, demonstrating the flexibility of this particular [[Polymorphism (biology)|polymorphism]].<ref>{{cite journal | last1=Rissing | first1=Steven W | name-list-style=vanc | year=1984 | title=Replete caste production and allometry of workers in the Honey Ant, ''Myrmecocystus mexicanus'' Wesmael (Hymenoptera: Formicidae) |  journal=Journal of the Kansas Entomological Society | volume=57 | issue=2| pages=347–350}}</ref> This polymorphism in morphology and behaviour of workers initially was thought to be determined by environmental factors such as nutrition and hormones that led to different [[morphogenesis|developmental paths]]; however, genetic differences between worker castes have been noted in ''Acromyrmex'' sp.<ref>{{cite journal | vauthors = Hughes WO, Sumner S, Van Borm S, Boomsma JJ | title = Worker caste polymorphism has a genetic basis in Acromyrmex leaf-cutting ants | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 100 | issue = 16 | pages = 9394–9397 | date = August 2003 | pmid = 12878720 | pmc = 170929 | doi = 10.1073/pnas.1633701100 | bibcode = 2003PNAS..100.9394H | doi-access = free }}</ref> These polymorphisms are caused by relatively small genetic changes; differences in a single gene of ''[[Red imported fire ant|Solenopsis invicta]]'' can decide whether the colony will have single or multiple queens.<ref>{{cite journal | vauthors = Ross KG, Krieger MJ, Shoemaker DD | title = Alternative genetic foundations for a key social polymorphism in fire ants | journal = Genetics | volume = 165 | issue = 4 | pages = 1853–1867 | date = December 2003 | doi = 10.1093/genetics/165.4.1853 | pmid = 14704171 | pmc = 1462884 }}</ref> The Australian [[jack jumper ant]] (''Myrmecia pilosula'') has only a single pair of chromosomes (with the males having just one chromosome as they are [[haploid]]), the lowest number known for any animal, making it an interesting subject for studies in the genetics and developmental biology of social insects.<ref>{{cite journal | vauthors = Crosland MW, Crozier RH | title = ''Myrmecia pilosula'', an ant with only one Pair of chromosomes | journal = Science | volume = 231 | issue = 4743 | pages = 1278 | date = March 1986 | pmid = 17839565 | doi = 10.1126/science.231.4743.1278 | bibcode = 1986Sci...231.1278C | s2cid = 25465053 }}</ref><ref>{{cite journal | vauthors = Tsutsui ND, Suarez AV, Spagna JC, Johnston JS | title = The evolution of genome size in ants | journal = BMC Evolutionary Biology | volume = 8 | issue = 64 | pages = 64 | date = February 2008 | pmid = 18302783 | pmc = 2268675 | doi = 10.1186/1471-2148-8-64 | doi-access = free | bibcode = 2008BMCEE...8...64T }}</ref>

===Genome size===
[[Genome size]] is a fundamental characteristic of an organism. Ants have been found to have tiny genomes, with the evolution of genome size suggested to occur through loss and accumulation of [[non-coding DNA|non-coding]] regions, mainly [[transposable element]]s, and occasionally by whole genome duplication.<ref name="moura">{{cite journal|author1=Moura, Mariana Neves|author2=Cardoso, Danon Clemes|author3=Cristiano, Maykon Passos|title=The tight genome size of ants: diversity and evolution under ancestral state reconstruction and base composition|year=2021|journal=Zoological Journal of the Linnean Society|volume=193|issue=1|pages=124–144|doi=10.1093/zoolinnean/zlaa135|issn=0024-4082|url=https://academic.oup.com/zoolinnean/article/193/1/124/6036549}}</ref> This may be related to [[Colonisation (biology)|colonisation]] processes, but further studies are needed to verify this.<ref name="moura"/>