Editing Ant (section)

===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>