Editing Red imported fire ant (section)

===Polymorphism===
[[File:Anatomical differences of S. invicta workers.png|thumbnail|230px|left|Anatomical differences of red imported fire ant workers: The scale bar is 1 mm.]]

The red imported fire ant is polymorphic with two different castes of workers: minor workers and major workers (soldiers). Like many ants that exhibit polymorphism, young, smaller ants do not forage and tend to the brood instead, while the larger workers go out and forage.<ref>{{cite journal|last1=Mirenda|first1=J.T.|last2=Vinson|first2=S.B.|title=Division of labour and specification of castes in the red imported fire ant ''Solenopsis invicta'' Buren|journal=Animal Behaviour|date=1981|volume=29|issue=2|pages=410–420|doi=10.1016/S0003-3472(81)80100-5|s2cid=53199246}}</ref>{{sfn|Schmid-Hempel|1998|p=144}}{{sfn|Hölldobler|Wilson|1990|p=311}}{{sfn|Hölldobler|Wilson|1990|p=318}} In incipient colonies, polymorphism does not exist, but instead they are occupied by monomorphic workers called "minims" or "nanitics". The average head-width in tested colonies increases during the first six months of development.<ref name="Tschinkel_1988">{{cite journal|last1=Tschinkel|first1=W.R.|title=Colony growth and the ontogeny of worker polymorphism in the fire ant, ''Solenopsis invicta''|url=https://archive.org/details/sim_behavioral-ecology-and-sociobiology_1988-02_22_2/page/103|journal=Behavioral Ecology and Sociobiology|date=1988|volume=22|issue=2|pages=103–115|doi=10.1007/BF00303545|bibcode=1988BEcoS..22..103T |s2cid=8455126}}</ref><ref name="Tschinkel_et_al_2003"/> In five-year-old colonies, the head width of minor workers decreases, but for major workers, the head-width remains the same. The total weight of a major worker is twice that of a minor worker when they first arrive, and by six months, major workers are four times heavier than minor workers. Once major workers develop, they can make up a large portion of the workforce, with as many as 35% being major workers in a single colony.<ref name="Tschinkel_1988"/> This does not affect colony performance, as polymorphic colonies and nests with small workers produce broods at roughly the same rate, and polymorphism is not an advantage or disadvantage when food sources are not limited. However, polymorphic colonies are more energetically efficient, and under conditions where food is limited, polymorphism may provide a small advantage in brood production, but this depends on the levels of food stress.<ref>{{cite journal|last1=Porter|first1=S.D.|last2=Tschinkel|first2=W.R.|title=Fire ant polymorphism: the ergonomics of brood production|url=https://archive.org/details/sim_behavioral-ecology-and-sociobiology_1985-04_16_4/page/323|journal=Behavioral Ecology and Sociobiology|date=1985|volume=16|issue=4|pages=323–336|doi=10.1007/BF00295545|jstor=4599785|bibcode=1985BEcoS..16..323P |s2cid=5967997}}</ref>

As worker ants grow to larger sizes, the shape of the head changes, due to the head length growing at the same time as the total body length, and the head width may grow by 20%. The length of the antennae only grows slowly; the antennae may only grow 60% longer by the time the body doubles its length, thus the relative antennal length decreases by 20% as the length of the body doubles.<ref name="Tschinkel_et_al_2003">{{cite journal|last1=Tschinkel|first1=W.R.|last2=Mikheyev|first2=A.S.|last3=Storz|first3=S.R.|title=Allometry of workers of the fire ant, ''Solenopsis invicta''|journal=Journal of Insect Science|date=2003|volume=3|issue=2|pages=2|doi=10.1673/031.003.0201|pmid=15841219|pmc=524642}}</ref> All individual legs of the body are isometric with body length meaning that even when the length of the body doubles, the legs will also double. However, not all of the legs are the same length; the prothoracic portion accounts for 29% of leg length, the mesothoracic 31%, and the metathoracic 41%. The first two pairs of legs are of equal length to one another, whereas the final pair is longer.<ref name="Tschinkel_et_al_2003"/> Overall, the morphological appearance of a worker changes dramatically when it grows larger. The head exhibits the greatest shape change and the height of the [[Notum|alinotum]] grows quicker than its length, where a height/length ratio of 0.27 in minor workers and 0.32 in major workers is seen.<ref name="Tschinkel_et_al_2003"/> Due to this, larger workers tend to have a humped-shape and robust alinotum in contrast to smaller workers. No petiole segment exhibits any change in shape as the size of the body changes. The width of the gaster grows more rapidly than its length, where the width may be 96% of its length but increases to 106%.<ref name="Tschinkel_et_al_2003"/>