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[[File:Safari ants tunnel.jpg|thumb|upright|200px|African ''[[Dorylus]]'' raid]]
[[File:Safari ants tunnel.jpg|thumb|upright|200px|African ''[[Dorylus]]'' raid]]


The name '''army ant '''(or '''legionary ant''' or '''''marabunta'''''<ref>{{Cite web|url=https://www.disclose.tv/attack-of-legionary-ants-also-known-as-army-ants-or-marabunta-to-a-wasp-honeycomb-2018-341853|title=Attack Of Legionary Ants (also Known As Army Ants Or Marabunta) To A Wasp Honeycomb|date=2018-08-04|website=Disclose.tv|language=en|access-date=2019-04-04}}</ref>) is applied to over 200 [[ant]] species in different lineages. Because of their aggressive predatory foraging groups, known as "raids", a huge number of ants forage simultaneously over a limited area.<ref name="Schneirla, T. C. 1971" />
The name '''army ant '''(or '''legionary ant''' or '''''marabunta'''''<ref>{{Cite journal |last1=Dejean |first1=Alain |last2=Azémar |first2=Frédéric |last3=Roux |first3=Olivier |date=2014-07-01 |title=An invasive ant species able to counterattack marabunta raids |url= |journal=Comptes Rendus Biologies |language=en |volume=337 |issue=7 |pages=474–479 |doi=10.1016/j.crvi.2014.05.004 |pmid=25103833 |issn=1631-0691|doi-access=free }}</ref>) is applied to over 200 [[ant]] species in different lineages. Because of their aggressive predatory foraging groups, known as "raids", a huge number of ants forage simultaneously over a limited area.<ref name="Schneirla, T. C. 1971" />


Another shared feature is that, unlike most ant species, army ants do not construct permanent nests; an army ant colony moves almost incessantly over the time it exists. All species are members of the true ant family, [[Formicidae]], but several groups have independently evolved the same basic behavioural and ecological syndrome. This syndrome is often referred to as "legionary behaviour", and may be an example of [[convergent evolution]].<ref name=brady2003 />{{refn|group=n|"There are also interesting [evolutionary] convergences within the ants. Although most ant colonies live a settled existence in a fixed nest, there seems to be a successful living to be made by wandering in enormous pillaging armies. This is called the legionary habit." {{Harv|Dawkins|1986}}}}
Another shared feature is that, unlike most ant species, army ants do not construct permanent nests; an army ant colony moves almost incessantly over the time it exists. All species are members of the true ant family, [[Formicidae]], but several groups have independently evolved the same basic behavioural and ecological syndrome. This syndrome is often referred to as "legionary behaviour", and may be an example of [[convergent evolution]].<ref name=brady2003 />{{refn|group=n|"There are also interesting [evolutionary] convergences within the ants. Although most ant colonies live a settled existence in a fixed nest, there seems to be a successful living to be made by wandering in enormous pillaging armies. This is called the legionary habit." {{Harv|Dawkins|1986}}}}
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=== Males ===
=== Males ===
Males are large in size and have a large cylindrical abdomen, highly modified mandibles and uncommon genitalia not seen in other ants.<ref name="Trager, James C. 1988" /> They have 13 segments on their antennae, are [[alate]]d (have wings) and therefore can resemble [[wasp]]s.<ref name="Gotwald, William H. 1982" /> Males are born as part of a sexual brood.<ref name="Trager, James C. 1988" /> As soon as they are born, they will fly off in search of a queen to mate with. In some instances where males seek to mate with a queen from an existing colony, the receiving workers will forcibly remove the wings in order to accommodate the large males into the colony for mating.<ref name="Franks&Nigel&Holldobler_1987" /> Because of their size, males are sometimes called "sausage flies" or "sausage ants."<ref>{{Cite web|url=http://www.sheppardsoftware.com/content/animals/animals/breeds/ant_driverant.htm|title=Driver Ants - info and games|website=www.sheppardsoftware.com|access-date=2019-04-04}}</ref>
Males are large in size and have a large cylindrical abdomen, highly modified mandibles and uncommon genitalia not seen in other ants.<ref name="Trager, James C. 1988" /> They have 13 segments on their antennae, are [[alate]]d (have wings) and therefore can resemble [[wasp]]s.<ref name="Gotwald, William H. 1982" /> Males are born as part of a sexual brood.<ref name="Trager, James C. 1988" /> As soon as they are born, they will fly off in search of a queen to mate with. In some instances where males seek to mate with a queen from an existing colony, the receiving workers will forcibly remove the wings in order to accommodate the large males into the colony for mating.<ref name="Franks&Nigel&Holldobler_1987" /> Because of their size, males are sometimes called "sausage flies" or "sausage ants."<ref>{{Cite web|url=http://www.sheppardsoftware.com/content/animals/animals/breeds/ant_driverant.htm|title=Driver Ants info and games|website=www.sheppardsoftware.com|access-date=2019-04-04}}</ref>


=== Queen ===
=== Queen ===
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=== Army ant syndrome ===
=== Army ant syndrome ===
The army ant syndrome refers to [[behavioral]] and reproductive traits such as obligate collective foraging, [[nomadism]] and highly specialized queens that allow these organisms to become the most ferocious social hunters.<ref name=brady2003 />
The term "army ant syndrome" refers to [[behavioral]] and reproductive traits such as obligate collective foraging, [[nomadism]] and highly specialized queens that allow these organisms to become the most ferocious social hunters.<ref name=brady2003 />


Most ant species will send individual scouts to find food sources and later recruit others from the colony to help; however, army ants dispatch a cooperative, leaderless group of foragers to detect and overwhelm the prey at once.<ref name=brady2003 /><ref name="Gotwald, William H. 1982" /> Army ants do not have a permanent nest but instead form many [[bivouac (ants)|bivouacs]] as they travel. The constant traveling is due to the need to hunt large amounts of prey to feed its enormous colony [[population]].<ref name="Gotwald, William H. 1982" /> Their queens are wingless and have abdomens that expand significantly during egg production.<ref name="Franks&Nigel&Holldobler_1987" /> This allows for the production of 3–4 million eggs every month and often results in synchronized brood cycles, thus each colony will be formed of millions of individuals that descend from a single queen. These three traits are found in all army ant species and are the defining traits of army ants.<ref name=brady2003 /><ref name="Wilson&Hölldobler_2005" />
Most ant species will send individual scouts to find food sources and later recruit others from the colony to help; however, army ants dispatch a cooperative, leaderless group of foragers to detect and overwhelm the prey at once.<ref name=brady2003 /><ref name="Gotwald, William H. 1982" /> Army ants do not have a permanent nest but instead form many [[bivouac (ants)|bivouacs]] as they travel. The constant traveling is due to the need to hunt large amounts of prey to feed its enormous colony [[population]].<ref name="Gotwald, William H. 1982" /> Their queens are wingless and have abdomens that expand significantly during egg production.<ref name="Franks&Nigel&Holldobler_1987" /> This allows for the production of 3–4 million eggs every month and often results in synchronized brood cycles, thus each colony will be formed of millions of individuals that descend from a single queen. These three traits are found in all army ant species and are the defining traits of army ants.<ref name=brady2003 /><ref name="Wilson&Hölldobler_2005" />


==== Nomadic and stationary phase ====
==== Nomadic and stationary phase ====
Army ants have two phases of activity—a nomadic (wandering) phase and a stationary (statary) phase—that constantly cycle, and can be found throughout all army ant species.<ref name="Franks&Nigel&Holldobler_1987" />
Army ants have two phases of activity{{snd}}a nomadic (wandering) phase and a stationary (statary) phase{{snd}}that constantly cycle, and can be found throughout all army ant species.<ref name="Franks&Nigel&Holldobler_1987" />


The nomadic phase begins around 10 days after the queen lays her eggs. This phase will last approximately 15 days to let the larvae develop. The ants move during the day, capturing [[insects]], [[spiders]], and small [[vertebrates]] to feed their brood. At dusk, they will form their nests or bivouac, which they change almost daily.<ref name="Franks&Nigel&Holldobler_1987" /> At the end of the nomadic phase, the larvae will spin pupal cases and no longer require food. The colony can then live in the same bivouac site for around 20 days, foraging only on approximately two-thirds of these days.<ref name="Schneirla, T. C. 1971" /><ref name="Franks&Nigel&Holldobler_1987" /> Among the army ants are some species that venture out only at night, but no adequate studies of their activities have been made.
The nomadic phase begins around 10 days after the queen lays her eggs. This phase will last approximately 15 days to let the larvae develop. The ants move during the day, capturing [[insects]], [[spiders]], and small [[vertebrates]] to feed their brood. At dusk, they will form their nests or bivouac, which they change almost daily.<ref name="Franks&Nigel&Holldobler_1987" /> At the end of the nomadic phase, the larvae will spin pupal cases and no longer require food. The colony can then live in the same bivouac site for around 20 days, foraging only on approximately two-thirds of these days.<ref name="Schneirla, T. C. 1971" /><ref name="Franks&Nigel&Holldobler_1987" /> This pattern of [[Diurnality|diurnal]] activity does not apply to all army ants: there are also species that forage at night ([[Nocturnality|nocturnal]]) or at both day and night ([[Cathemerality|cathemeral]]).<ref name=":1">{{Cite journal |last1=O'Donnell |first1=Sean |last2=Lattke |first2=John |last3=Powell |first3=Scott |last4=Kaspari |first4=Michael |date=2021 |title=Diurnal and nocturnal foraging specialisation in Neotropical army ants |url=https://resjournals.onlinelibrary.wiley.com/doi/10.1111/een.12969 |journal=Ecological Entomology |language=en |volume=46 |issue=2 |pages=352–359 |doi=10.1111/een.12969 |bibcode=2021EcoEn..46..352O |issn=0307-6946}}</ref>


The stationary phase, which lasts about two to three weeks, begins when the [[larvae]] pupate. From this point on, the prey that were previously fed to the larvae are now fed exclusively to the queen.<ref name="Franks&Nigel&Holldobler_1987" /> The abdomen ([[gaster (insect anatomy)|gaster]]) of the queen swells significantly, and she lays her eggs. At the end of the stationary phase, both the pupae emerge from their cocoons ([[eclosion]]) and the next generation of eggs hatch so the colony has a new group of workers and larvae. After this, the ants resume the nomadic phase.<ref name="Gotwald, William H. 1982" /><ref name="Franks&Nigel&Holldobler_1987" />
The stationary phase, which lasts about two to three weeks, begins when the [[larvae]] pupate. From this point on, the prey that were previously fed to the larvae are now fed exclusively to the queen.<ref name="Franks&Nigel&Holldobler_1987" /> The abdomen ([[gaster (insect anatomy)|gaster]]) of the queen swells significantly, and she lays her eggs. At the end of the stationary phase, both the pupae emerge from their cocoons ([[eclosion]]) and the next generation of eggs hatch so the colony has a new group of workers and larvae. After this, the ants resume the nomadic phase.<ref name="Gotwald, William H. 1982" /><ref name="Franks&Nigel&Holldobler_1987" />
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=== Reproduction responsibilities and problems ===
=== Reproduction responsibilities and problems ===
In a [[colony (biology)|colony]], the queen is the primary individual responsible for reproduction in the colony. Analysis of genotypes have confirmed that workers are, on average, more closely related to the offspring of the queen than to that of other workers, and that workers rarely, if ever, reproduce.<ref name="Kronauer_et_al_2006" /> Three factors have been suggested to rationalize the loss of worker reproduction in the presence of a queen. First, if the worker reproduces, it lowers the general performance of the colony because it is not working. Second, workers increase their inclusive fitness by [[policing]] other workers because they themselves are more related to the queen’s offspring than other worker’s offspring.<ref name="Kronauer_et_al_2006" /> Lastly, the large male larvae become too large to be transported, forcing colonies with a sexual brood to nest for a period of 41–56 days, as compared to non-reproductive colonies that remain in the nest an average of 17 days before returning to a nomadic phase. This suggests that if workers produced male offspring, they might be hatched out of sync with the queen's sexual brood and not likely to be successfully reared to adulthood.<ref name="Kronauer_et_al_2006" />
In a [[colony (biology)|colony]], the queen is the primary individual responsible for reproduction in the colony. Analysis of genotypes have confirmed that workers are, on average, more closely related to the offspring of the queen than to that of other workers, and that workers rarely, if ever, reproduce.<ref name="Kronauer_et_al_2006" /> Three factors have been suggested to rationalize the loss of worker reproduction in the presence of a queen. First, if the worker reproduces, it lowers the general performance of the colony because it is not working. Second, workers increase their inclusive fitness by [[policing]] other workers because they themselves are more related to the queen's offspring than other worker's offspring.<ref name="Kronauer_et_al_2006" /> Lastly, the large male larvae become too large to be transported, forcing colonies with a sexual brood to nest for a period of 41–56 days, as compared to non-reproductive colonies that remain in the nest an average of 17 days before returning to a nomadic phase. This suggests that if workers produced male offspring, they might be hatched out of sync with the queen's sexual brood and not likely to be successfully reared to adulthood.<ref name="Kronauer_et_al_2006" />

=== Ant mills ===
{{Main|Ant mill}}
Army ants can get lost from the pheromone track while foraging, making the ants follow each other in a circular motion, potentially causing them to die of [[Fatigue|exhaustion]].<ref>{{cite journal|vauthors=Delsuc F |year=2003 |title=Army Ants Trapped by Their Evolutionary History| journal=PLOS Biology|volume=1|issue=2|page=e37 |doi=10.1371/journal.pbio.0000037 |pmid=14624241 |pmc=261877 |doi-access=free }}</ref>


== Foraging ==
== Foraging ==
The whole colony of army ants can consume up to 500,000 prey animals each day, so can have a significant influence on the [[population]], diversity, and behaviour of their prey.<ref name="Franks_ Fletcher" /> The prey selection differs with the species. Underground species prey primarily on ground-dwelling [[arthropods]] and their [[larvae]], [[earthworms]], and occasionally also the young of vertebrates, turtle eggs, or oily seeds. A majority of the species, the "colony robbers", specialize in the offspring of other [[ants]] and [[wasps]]. Only a few species seem to have the very broad spectrum of prey seen in the raiding species. Even these species do not eat every kind of animal. Although small vertebrates that get caught in the raid will be killed, the jaws of the American ''[[Eciton]]'' are not suited to this type of prey, in contrast to the African ''[[Dorylus]]''. These undesired prey are simply left behind and consumed by scavengers or by the flies that accompany the ant swarm. Only a few species hunt primarily on the surface of the earth; they seek their prey mainly in leaf litter and in low vegetation. About five species hunt in higher trees, where they can attack birds and their eggs, although they focus on hunting other social insects along with their eggs and larvae. Colonies of army ants are large compared to the colonies of other Formicidae. Colonies can have over 15 million workers and can transport 3000 prey (items) per hour during the raid period.<ref name="Kronauer&Johnson&Boomsma_2007" /><ref name="Couzin&Franks_2003" />
The whole colony of army ants can consume up to 500,000 prey animals each day, so can have a significant influence on the [[population]], diversity, and behaviour of their prey.<ref name="Franks_ Fletcher" /> The prey selection differs with the species. Underground species prey primarily on ground-dwelling [[arthropods]] and their [[larvae]], [[earthworms]], and occasionally also the young of vertebrates, turtle eggs, or oily seeds. A majority of the species, the "colony robbers", specialize in the offspring of other [[ants]] and [[wasps]]. Only a few species seem to have the very broad spectrum of prey seen in the raiding species. Even these species do not eat every kind of animal. Although small vertebrates that get caught in the raid will be killed, the jaws of the American ''[[Eciton]]'' are not suited to this type of prey, in contrast to the African ''[[Dorylus]]''. These undesired prey are simply left behind and consumed by scavengers or by the flies that accompany the ant swarm. Only a few species hunt primarily on the surface of the earth; they seek their prey mainly in leaf litter and in low vegetation. About five species hunt in higher trees, where they can attack birds and their eggs, although they focus on hunting other social insects along with their eggs and larvae. Colonies of army ants are large compared to the colonies of other Formicidae. Colonies can have over 15 million workers and can transport 3000 prey (items) per hour during the raid period.<ref name="Kronauer&Johnson&Boomsma_2007" /><ref name="Couzin&Franks_2003" />


When army ants forage, the trails that are formed can be over {{Convert|20|m|ft|abbr=on}} wide and over {{Convert|100|m|ft|abbr=on}} long.<ref name="Couzin&Franks_2003" /> They stay on the path through the use of a concentration gradient of pheromones. The concentration of pheromone is highest in the middle of the trail, splitting the trail into two distinct regions: an area with high concentration and two areas with low concentrations of pheromones. The outbound ants will occupy the outer two lanes and the returning ants will occupy the central lane.<ref name="Couzin&Franks_2003" /> The returning worker ants have also been found to emit more pheromones than those leaving the nest, causing the difference in concentration of pheromone in the trails.<ref name="Deneubourg_et_al_1989" /> The pheromones will allow foraging to be much more efficient by allowing the army ants to avoid their own former paths and those of their conspecifics.<ref name="Franks_ Fletcher" /> Scaffolds structure has been observed when workers carried heavy prey food to inclined surface.Walking ants are prevented from falling by other ants.<ref>{{Cite web|last1=Reid|first1=Chris|last2=Carlesso|first2=Daniele|title=Bridges, highways, scaffolds: how the amazing engineering of army ants can make us smarter creators|url=http://theconversation.com/bridges-highways-scaffolds-how-the-amazing-engineering-of-army-ants-can-make-us-smarter-creators-158326|access-date=2021-04-20|website=The Conversation|language=en}}</ref>
When army ants forage, the trails that are formed can be over {{Convert|20|m|ft|abbr=on}} wide and over {{Convert|100|m|ft|abbr=on}} long.<ref name="Couzin&Franks_2003" /> They stay on the path through the use of a concentration gradient of pheromones. The concentration of pheromone is highest in the middle of the trail, splitting the trail into two distinct regions: an area with high concentration and two areas with low concentrations of pheromones. The outbound ants will occupy the outer two lanes and the returning ants will occupy the central lane.<ref name="Couzin&Franks_2003" /> The returning worker ants have also been found to emit more pheromones than those leaving the nest, causing the difference in concentration of pheromone in the trails.<ref name="Deneubourg_et_al_1989" /> The pheromones will allow foraging to be much more efficient by allowing the army ants to avoid their own former paths and those of their conspecifics.<ref name="Franks_ Fletcher" /> Scaffolds structure has been observed when workers carried heavy prey food to inclined surface. Walking ants are prevented from falling by other ants.<ref>{{Cite web|last1=Reid|first1=Chris|last2=Carlesso|first2=Daniele|title=Bridges, highways, scaffolds: how the amazing engineering of army ants can make us smarter creators|url=http://theconversation.com/bridges-highways-scaffolds-how-the-amazing-engineering-of-army-ants-can-make-us-smarter-creators-158326|access-date=2021-04-20|website=The Conversation |date=April 19, 2021 |language=en}}</ref>


While foraging, army ants cause many invertebrates to flee from their hiding places under leaves of the forest floor, under tree bark, and other such locations, thereby allowing predators to catch them more easily. For example, in the tropical rainforests of Panama, swarms of army ants attract many species of birds to this feast of scrambling insects, spiders, scorpions, worms, and other animals. Some of these birds are named “antbirds” due to this tendency.<ref>Angehr G, Dean R. 2010. The birds of Panama: a field guide. Cornell Univ. Press, Ithaca, New Yori, USA. 456 pp.</ref> While focused on feeding on these invertebrates, birds at army-ant swarms typically allow very close approach by people—within {{Convert|1–2|m|ft|abbr=out}} in many cases—often providing the best opportunities to see many of these species. Depending on the size of the ant swarm and the amount of prey the ants stir up, birds can number from a few to dozens of individuals. Birds that frequent army-ant swarms include the [[white-whiskered puffbird]], [[rufous motmot]], [[rufous-vented ground cuckoo]], [[grey-cowled wood rail]], [[plain-brown woodcreeper]], [[northern barred woodcreeper]], [[cocoa woodcreeper]], [[black-striped woodcreeper]], [[fasciated antshrike]], [[black-crowned antshrike]], [[spotted antbird]], [[bicolored antbird]], [[ocellated antbird]], [[chestnut-backed antbird]], [[black-faced antthrush]], and [[gray-headed tanager]].<ref>Kent Livezey, Birding Pipeline Panama, East Coast Tower, Costa del Este, Panama City, Panama 33192-4177</ref>
While foraging, army ants cause many invertebrates to flee from their hiding places under leaves of the forest floor, under tree bark, and other such locations, thereby allowing predators to catch them more easily. For example, in the tropical rainforests of Panama, swarms of army ants attract many species of birds to this feast of scrambling insects, spiders, scorpions, worms, and other animals. Some of these birds are named "antbirds" due to this tendency.<ref>{{Cite book |last1=Angehr |first1=George Richard |title=The birds of Panama: a field guide |last2=Dean |first2=Robert |date=2010 |publisher=Comstock Pub. Associates |isbn=978-0-8014-7674-7 |location=Ithaca}}</ref> While focused on feeding on these invertebrates, birds at army-ant swarms typically allow very close approach by people{{snd}}within {{Convert|1–2|m|ft|abbr=out}} in many cases{{snd}}often providing the best opportunities to see many of these species. Depending on the size of the ant swarm and the amount of prey the ants stir up, birds can number from a few to dozens of individuals. Birds that frequent army-ant swarms include the [[white-whiskered puffbird]], [[rufous motmot]], [[rufous-vented ground cuckoo]], [[grey-cowled wood rail]], [[plain-brown woodcreeper]], [[northern barred woodcreeper]], [[cocoa woodcreeper]], [[black-striped woodcreeper]], [[fasciated antshrike]], [[black-crowned antshrike]], [[spotted antbird]], [[bicolored antbird]], [[ocellated antbird]], [[chestnut-backed antbird]], [[black-faced antthrush]], and [[gray-headed tanager]].<ref>Kent Livezey, ''Birding Pipeline Panama'', Panama City, Panama{{ISBN?}}{{Page?|date=June 2022}}</ref>


== Nesting ==
== Nesting ==
[[File:Ant bridge.jpg|thumb|''[[Eciton]]'' sp. forming a bridge]]
[[File:Ant bridge.jpg|thumb|''[[Eciton]]'' sp. forming a bridge]]
Army ants do not build a nest like most other ants. Instead, they build a living nest with their bodies, known as a [[Bivouac (ants)|bivouac]]. Bivouacs tend to be found in tree trunks or in burrows dug by the ants. The members of the bivouac hold onto each other's legs and so build a sort of ball, which may look unstructured to a layman's eyes, but is actually a well-organized structure.<ref name="dawkins1986" /> The older female workers are located on the exterior; in the interior are the younger female workers. At the smallest disturbance, soldiers gather on the top surface of the bivouac, ready to defend the nest with powerful [[Mandible (arthropod mouthpart)|mandibles]] and (in the case of the [[Aenictinae]] and [[Ecitoninae]]) stingers. Inside the nest, there are numerous passages that have 'chambers' of food, larvae, eggs, and most importantly, the queen.<ref>{{Cite web|url=https://www.kaieteurnewsonline.com/2013/08/11/the-army-ant/|title=The Army Ant|date=2013-08-11|website=Kaieteur News|language=en-US|access-date=2019-04-04}}</ref>
Army ants do not build a nest like most other ants. Instead, they build a living nest with their bodies, known as a [[Bivouac (ants)|bivouac]]. Bivouacs tend to be found in tree trunks or in burrows dug by the ants. The members of the bivouac hold onto each other's legs and so build a sort of ball, which may look unstructured to a layman's eyes, but is actually a well-organized structure.<ref name="dawkins1986" /> The older female workers are located on the exterior; in the interior are the younger female workers. At the smallest disturbance, soldiers gather on the top surface of the bivouac, ready to defend the nest with powerful [[Mandible (arthropod mouthpart)|mandibles]] and (in the case of the [[Ecitoninae]]) stingers. Inside the nest, there are numerous passages that have 'chambers' of food, larvae, eggs, and most importantly, the queen.<ref>{{Cite web|url=https://www.kaieteurnewsonline.com/2013/08/11/the-army-ant/|title=The Army Ant|date=2013-08-11|website=Kaieteur News|language=en-US|access-date=2019-04-04}}</ref>


== Symbionts ==
== Symbionts ==
Many species of army ants are widely considered to be [[keystone species]]<ref>{{Cite journal|last=Pérez-Espona|first=Sílvia|date=March 2021|title=Eciton Army Ants—Umbrella Species for Conservation in Neotropical Forests|journal=Diversity|language=en|volume=13|issue=3|pages=136|doi=10.3390/d13030136|doi-access=free}}</ref> due to their important ecological role as arthropod predators <ref>{{Cite journal|last1=Hoenle|first1=Philipp O.|last2=Blüthgen|first2=Nico|last3=Brückner|first3=Adrian|last4=Kronauer|first4=Daniel J. C.|last5=Fiala|first5=Brigitte|last6=Donoso|first6=David A.|last7=Smith|first7=M. Alex|last8=Jara|first8=Bryan Ospina|last9=Beeren|first9=Christoph von|date=2019|title=Species-level predation network uncovers high prey specificity in a Neotropical army ant community|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.15078|journal=Molecular Ecology|language=en|volume=28|issue=9|pages=2423–2440|doi=10.1111/mec.15078|pmid=31050080|s2cid=143433968|issn=1365-294X}}</ref> and due to their large number of vertebrate and invertebrate associates that rely on army ant colonies for nutrition or protection.<ref name="Boswell et al. 1998" /><ref>{{Cite journal|last1=von Beeren|first1=Christoph|last2=Blüthgen|first2=Nico|last3=Hoenle|first3=Philipp O.|last4=Pohl|first4=Sebastian|last5=Brückner|first5=Adrian|last6=Tishechkin|first6=Alexey K.|last7=Maruyama|first7=Munetoshi|last8=Brown|first8=Brian V.|last9=Hash|first9=John M.|last10=Hall|first10=W. E.|last11=Kronauer|first11=Daniel J. C.|title=A remarkable legion of guests: Diversity and host specificity of army ant symbionts|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.16101|journal=Molecular Ecology|year=2021|volume=30|issue=20|pages=5229–5246|language=en|doi=10.1111/mec.16101|pmid=34406688|s2cid=237199045|issn=1365-294X}}</ref><ref name=":0">{{Cite journal|last1=Rettenmeyer|first1=C. W.|last2=Rettenmeyer|first2=M. E.|last3=Joseph|first3=J.|last4=Berghoff|first4=S. M.|date=2011-08-01|title=The largest animal association centered on one species: the army ant Eciton burchellii and its more than 300 associates|url=https://doi.org/10.1007/s00040-010-0128-8|journal=Insectes Sociaux|language=en|volume=58|issue=3|pages=281–292|doi=10.1007/s00040-010-0128-8|s2cid=32688600|issn=1420-9098}}</ref> During their hunt, many surface-raiding army ants are accompanied by various birds, such as [[antbirds]], [[thrushes]], [[ovenbirds]] and [[wrens]], which devour the insects that are flushed out by the ants, a behavior known as [[kleptoparasitism]].<ref name="Wrege et al. 2005" /><ref>{{Cite journal |last1=Willis |first1=Edwin O. |author-link=Edwin O'Neill Willis |last2=Oniki |first2=Yoshika |date=1978 |title=Birds and Army Ants |url=https://www.researchgate.net/publication/234150379 |journal=Annual Review of Ecology and Systematics |volume=9 |issue=1 |pages=243–263 |doi=10.1146/annurev.es.09.110178.001331 |issn=0066-4162 |via=ResearchGate}}</ref> A wide variety of arthropods including [[staphylinid]] beetles, histerid beetles, spiders, silverfish, isopods, and [[mites]] also follow colonies.<ref>{{Cite book|last=Kronauer|first=Daniel J. C.|url=https://www.worldcat.org/oclc/1224277932|title=Army Ants|date=2020|isbn=978-0-674-24941-7|location=Cambridge, MA|oclc=1224277932}}</ref> While some guests follow the colony emigrations on foot,<ref>{{Cite journal|last1=von Beeren|first1=Christoph|last2=Maruyama|first2=Munetoshi|last3=Kronauer|first3=Daniel J. C.|date=2016|title=Cryptic diversity, high host specificity and reproductive synchronization in army ant-associated Vatesus beetles|url=https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.13500|journal=Molecular Ecology|language=en|volume=25|issue=4|pages=990–1005|doi=10.1111/mec.13500|pmid=26618779|s2cid=22773782|issn=1365-294X}}</ref><ref>{{Cite journal|last1=von Beeren|first1=Christoph|last2=Maruyama|first2=Munetoshi|last3=Kronauer|first3=Daniel J. C.|date=2016-11-09|title=Community Sampling and Integrative Taxonomy Reveal New Species and Host Specificity in the Army Ant-Associated Beetle Genus Tetradonia (Coleoptera, Staphylinidae, Aleocharinae)|journal=PLOS ONE|language=en|volume=11|issue=11|pages=e0165056|doi=10.1371/journal.pone.0165056|issn=1932-6203|pmc=5102370|pmid=27829037|bibcode=2016PLoSO..1165056V|doi-access=free}}</ref><ref name=":0" /> many others are phoretically transported, for example by attaching themseles on army ant workers such as the histerid beetle ''[[Nymphister kronaueri]]''.<ref>{{Cite journal|last1=von Beeren|first1=Christoph|last2=Tishechkin|first2=Alexey K.|date=2017-02-10|title=Nymphister kronaueri von Beeren & Tishechkin sp. nov., an army ant-associated beetle species (Coleoptera: Histeridae: Haeteriinae) with an exceptional mechanism of phoresy|journal=BMC Zoology|volume=2|issue=1|pages=3|doi=10.1186/s40850-016-0010-x|issn=2056-3132|doi-access=free}}</ref> The [[Neotropical]] army ant ''[[Eciton burchellii]]'' has an estimated 350 to 500 animal associates, the most of any one species known to science.<ref name=":0" />
Many species of army ants are widely considered to be [[keystone species]]<ref>{{Cite journal|last=Pérez-Espona|first=Sílvia|date=March 2021|title=Eciton Army Ants – Umbrella Species for Conservation in Neotropical Forests|journal=Diversity|language=en|volume=13|issue=3|pages=136|doi=10.3390/d13030136|doi-access=free|hdl=20.500.11820/be179574-8ff7-4531-b575-8ebecc801e3d|hdl-access=free}}</ref> due to their important ecological role as arthropod predators <ref>{{Cite journal|last1=Hoenle|first1=Philipp O.|last2=Blüthgen|first2=Nico|last3=Brückner|first3=Adrian|last4=Kronauer|first4=Daniel J. C.|last5=Fiala|first5=Brigitte|last6=Donoso|first6=David A.|last7=Smith|first7=M. Alex|last8=Jara|first8=Bryan Ospina|last9=Beeren|first9=Christoph von|date=2019|title=Species-level predation network uncovers high prey specificity in a Neotropical army ant community|url=https://resolver.caltech.edu/CaltechAUTHORS:20190513-084120939|journal=Molecular Ecology|language=en|volume=28|issue=9|pages=2423–2440|doi=10.1111/mec.15078|pmid=31050080|bibcode=2019MolEc..28.2423H |s2cid=143433968|issn=1365-294X}}</ref> and due to their large number of vertebrate and invertebrate associates that rely on army ant colonies for nutrition or protection.<ref name="Boswell et al. 1998" /><ref>{{Cite journal|last1=von Beeren|first1=Christoph|last2=Blüthgen|first2=Nico|last3=Hoenle|first3=Philipp O.|last4=Pohl|first4=Sebastian|last5=Brückner|first5=Adrian|last6=Tishechkin|first6=Alexey K.|last7=Maruyama|first7=Munetoshi|last8=Brown|first8=Brian V.|last9=Hash|first9=John M.|last10=Hall|first10=W. E.|last11=Kronauer|first11=Daniel J. C.|title=A remarkable legion of guests: Diversity and host specificity of army ant symbionts|journal=Molecular Ecology|year=2021|volume=30|issue=20|pages=5229–5246|language=en|doi=10.1111/mec.16101|pmid=34406688|s2cid=237199045|issn=1365-294X|doi-access=free|bibcode=2021MolEc..30.5229V }}</ref><ref name=":0">{{Cite journal|last1=Rettenmeyer|first1=C. W.|last2=Rettenmeyer|first2=M. E.|last3=Joseph|first3=J.|last4=Berghoff|first4=S. M.|date=2011-08-01|title=The largest animal association centered on one species: the army ant Eciton burchellii and its more than 300 associates|url=https://doi.org/10.1007/s00040-010-0128-8|journal=Insectes Sociaux|language=en|volume=58|issue=3|pages=281–292|doi=10.1007/s00040-010-0128-8|s2cid=32688600|issn=1420-9098|url-access=subscription}}</ref> During their hunt, many surface-raiding army ants are accompanied by various birds, such as [[antbirds]], [[thrushes]], [[ovenbirds]] and [[wrens]], which devour the insects that are flushed out by the ants, a behavior known as [[kleptoparasitism]].<ref name="Wrege et al. 2005" /><ref>{{Cite journal |last1=Willis |first1=Edwin O. |author-link=Edwin O'Neill Willis |last2=Oniki |first2=Yoshika |date=1978 |title=Birds and Army Ants |url=https://www.researchgate.net/publication/234150379 |journal=Annual Review of Ecology and Systematics |volume=9 |issue=1 |pages=243–263 |doi=10.1146/annurev.es.09.110178.001331 |bibcode=1978AnRES...9..243W |issn=0066-4162 |via=ResearchGate}}</ref> A wide variety of arthropods including [[staphylinid]] beetles, histerid beetles, spiders, silverfish, isopods, and [[mites]] also follow colonies.<ref>{{Cite book|last=Kronauer|first=Daniel J. C.|url=https://www.worldcat.org/oclc/1224277932|title=Army Ants|date=2020|isbn=978-0-674-24941-7|location=Cambridge, MA|oclc=1224277932}}</ref> While some guests follow the colony emigrations on foot,<ref>{{Cite journal|last1=von Beeren|first1=Christoph|last2=Maruyama|first2=Munetoshi|last3=Kronauer|first3=Daniel J. C.|date=2016|title=Cryptic diversity, high host specificity and reproductive synchronization in army ant-associated Vatesus beetles|url=|journal=Molecular Ecology|language=en|volume=25|issue=4|pages=990–1005|doi=10.1111/mec.13500|pmid=26618779|bibcode=2016MolEc..25..990V |s2cid=22773782|issn=1365-294X}}</ref><ref>{{Cite journal|last1=von Beeren|first1=Christoph|last2=Maruyama|first2=Munetoshi|last3=Kronauer|first3=Daniel J. C.|date=2016-11-09|title=Community Sampling and Integrative Taxonomy Reveal New Species and Host Specificity in the Army Ant-Associated Beetle Genus Tetradonia (Coleoptera, Staphylinidae, Aleocharinae)|journal=PLOS ONE|language=en|volume=11|issue=11|pages=e0165056|doi=10.1371/journal.pone.0165056|issn=1932-6203|pmc=5102370|pmid=27829037|bibcode=2016PLoSO..1165056V|doi-access=free}}</ref><ref name=":0" /> many others are phoretically transported, for example by attaching themselves on army ant workers such as the histerid beetle ''[[Nymphister kronaueri]]''.<ref>{{Cite journal|last1=von Beeren|first1=Christoph|last2=Tishechkin|first2=Alexey K.|date=2017-02-10|title=Nymphister kronaueri von Beeren & Tishechkin sp. nov., an army ant-associated beetle species (Coleoptera: Histeridae: Haeteriinae) with an exceptional mechanism of phoresy|journal=BMC Zoology|volume=2|issue=1|pages=3|doi=10.1186/s40850-016-0010-x|issn=2056-3132|doi-access=free}}</ref> The [[Neotropical]] army ant ''[[Eciton burchellii]]'' has an estimated 350 to 500 animal associates, the most of any one species known to science.<ref name=":0" />

It has been speculated that the nocturnal foraging of some army ant species is done to reduce kleptoparasitism by birds, since the bird kleptoparasites of army ants are diurnal.<ref name=":1" />


== Taxonomy ==
== Taxonomy ==
Historically, "army ant" in the broad sense referred to various members of five different ant subfamilies. In two of these cases, the [[Ponerinae]] and [[Myrmicinae]], only a few species and genera exhibit legionary behavior; in the other three lineages, [[Ecitoninae]], [[Dorylinae]], and [[Leptanillinae]], all of the constituent species were considered to be legionary. More recently, ant classifications now recognize an additional New World subfamily, [[Leptanilloidinae]], which also consists of obligate legionary species, so is another group now included among the army ants.<ref>{{Cite journal|last=J.C Kronauer|first=Daniel|s2cid=17965336|date=10 November 2008 |title=Recent advances in army ant biology (Hymenoptera: Formicidae)|journal=Myrmecological News|volume=12|pages=51–65 |issn=1994-4136 |eissn=1997-3500 }}</ref>
Historically, "army ant" in the broad sense referred to various members of five different ant subfamilies. In two of these cases, the [[Ponerinae]] and [[Myrmicinae]], only a few species and genera exhibit legionary behavior; in the other three lineages, [[Ecitoninae]], [[Dorylinae]], and [[Leptanillinae]], all of the constituent species were considered to be legionary. More recently, ant classifications now recognize an additional New World subfamily, [[Leptanilloidinae]], which also consists of obligate legionary species, so is another group now included among the army ants.<ref name="Kronauer_2009" />


A 2003 study of thirty species (by Sean Brady of [[Cornell University]]) indicates that army ants of subfamilies [[Ecitoninae]] (South America), [[Dorylinae]] (Africa) and [[Aenictinae]] (Asia) together formed a [[monophyletic]] group, based on data from three molecular genes and one mitochondrial gene. Brady concluded that these groups are, therefore, a single lineage that evolved in the mid-Cretaceous period in [[Gondwana]],{{refn|group=n|"Because army ants are found almost everywhere, scientists postulated that they evolved many times after the break-up and dispersal of the supercontinent Gondwana just over 100 million years ago. The conventional view of the evolution of army ants needs a revision because of new data obtained by Sean Brady, a Cornell University, US, entomologist who has discovered that these ants evolved from a common ancestor."{{Harv|Whitehouse|2003}}<ref>{{cite news |first= David |last= Whitehouse |title= Ant history revealed |url= http://news.bbc.co.uk/2/hi/science/nature/3014011.stm |work= BBC News Online |department= Science & Environment |date= 2003-05-10 |access-date= 2009-01-14 }}</ref>}} so these subfamilies are now generally united into a single subfamily [[Dorylinae]], though this is still not universally recognized.<ref name="engel2005" /> However, the unification of these lineages means that the only subfamily that is composed solely of legionary species is Leptanillinae, as Dorylinae contains many non-legionary genera.
A 2003 study of thirty species (by Sean Brady of [[Cornell University]]) indicates that army ants of subfamilies [[Ecitoninae]] (South America), [[Dorylinae]] (Africa) and [[Aenictinae]] (Asia) together formed a [[monophyletic]] group, based on data from three molecular genes and one mitochondrial gene. Brady concluded that these groups are, therefore, a single lineage that evolved in the mid-Cretaceous period in [[Gondwana]],{{refn|group=n|"Because army ants are found almost everywhere, scientists postulated that they evolved many times after the break-up and dispersal of the supercontinent Gondwana just over 100 million years ago. The conventional view of the evolution of army ants needs a revision because of new data obtained by Sean Brady, a Cornell University, US, entomologist who has discovered that these ants evolved from a common ancestor."{{Harv|Whitehouse|2003}}<ref>{{cite news |first= David |last= Whitehouse |title= Ant history revealed |url= http://news.bbc.co.uk/2/hi/science/nature/3014011.stm |work= BBC News Online |department= Science & Environment |date= 2003-05-10 |access-date= 2009-01-14 }}</ref>}} so these subfamilies are now generally united into a single subfamily [[Dorylinae]], though this is still not universally recognized.<ref name="engel2005" /> However, the unification of these lineages means that the only subfamily that is composed solely of legionary species is Leptanillinae, as Dorylinae contains many non-legionary genera.
Line 88: Line 94:
Accordingly, the "army ants" as presently recognized consist of legionary species in these genera:
Accordingly, the "army ants" as presently recognized consist of legionary species in these genera:


; Subfamily [[Dorylinae]] (Aenictinae, Aenictogitoninae, Cerapachyinae, Ecitoninae and Leptanilloidinae, 2014)<ref name="Brady_et_al_2014">{{Cite journal | last1 = Brady | first1 = Seán G | last2 =Fisher | first2 = Brian L | last3 =Schultz | first3 = Ted R | last4 =Ward | first4 = Philip S | year = 2014 | title = The rise of army ants and their relatives: diversification of specialized predatory doryline ants | journal = BMC Evolutionary Biology | volume = 14 | pages = 2–14 | doi = 10.1186/1471-2148-14-93 | pmid = 24886136 | pmc = 4021219 }}</ref>
; Subfamily [[Dorylinae]] (Aenictinae, Aenictogitoninae, Cerapachyinae, Ecitoninae and Leptanilloidinae, 2014)<ref name="Brady_et_al_2014">{{Cite journal | last1 = Brady | first1 = Seán G | last2 =Fisher | first2 = Brian L | last3 =Schultz | first3 = Ted R | last4 =Ward | first4 = Philip S | year = 2014 | title = The rise of army ants and their relatives: diversification of specialized predatory doryline ants | journal = BMC Evolutionary Biology | volume = 14 | pages = 2–14 | doi = 10.1186/1471-2148-14-93 | pmid = 24886136 | pmc = 4021219 | doi-access = free | bibcode = 2014BMCEE..14...93B }}</ref>
* ''[[Aenictus]]''
* ''[[Aenictus]]''
* ''[[Asphinctanilloides]]''
* ''[[Asphinctanilloides]]''
Line 115: Line 121:
; Subfamily Amblyoponinae:
; Subfamily Amblyoponinae:
* ''[[Onychomyrmex]]''
* ''[[Onychomyrmex]]''

==See also==
* "[[Leiningen Versus the Ants]]" – fanciful 1938 short story by [[Carl Stephenson (author)|Carl Stephenson]] about soldier ants swarming over a Brazilian plantation


== Notes ==
== Notes ==
Line 124: Line 133:
<ref name="dawkins1986">{{cite book | last = Dawkins | first = Richard | author-link = Richard Dawkins | title = The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design | orig-year = 1986 | year = 1996 | publisher = [[W. W. Norton & Company]] | isbn = 978-0-393-31570-7 |page= [https://books.google.com/books?id=sPpaZnZMDG0C&dq=0140291229&pg=PA107 107] |chapter= 4. Making Tracks Through Animal Space |ref= {{Harvid|Dawkins|1986}}| title-link = The Blind Watchmaker }}</ref>
<ref name="dawkins1986">{{cite book | last = Dawkins | first = Richard | author-link = Richard Dawkins | title = The Blind Watchmaker: Why the Evidence of Evolution Reveals a Universe Without Design | orig-year = 1986 | year = 1996 | publisher = [[W. W. Norton & Company]] | isbn = 978-0-393-31570-7 |page= [https://books.google.com/books?id=sPpaZnZMDG0C&dq=0140291229&pg=PA107 107] |chapter= 4. Making Tracks Through Animal Space |ref= {{Harvid|Dawkins|1986}}| title-link = The Blind Watchmaker }}</ref>


<ref name=brady2003>{{Cite journal |last1= Brady |first1= Seán G. |title = Evolution of the army ant syndrome: The origin and long-term evolutionary stasis of a complex of behavioral and reproductive adaptations |journal= Proceedings of the National Academy of Sciences of the United States of America |volume= 100 |issue = 11 |pages= 6575–9 |date=2003 |pmid= 12750466 |pmc= 164488 |doi= 10.1073/pnas.1137809100|bibcode= 2003PNAS..100.6575B |doi-access= free }}</ref>
<ref name=brady2003>{{Cite journal |last1= Brady |first1= Seán G. |title = Evolution of the army ant syndrome: The origin and long-term evolutionary stasis of a complex of behavioral and reproductive adaptations |journal= Proceedings of the National Academy of Sciences of the United States of America |volume= 100 |issue = 11 |pages= 6575–6579 |date=2003 |pmid= 12750466 |pmc= 164488 |doi= 10.1073/pnas.1137809100|bibcode= 2003PNAS..100.6575B |doi-access= free }}</ref>


<ref name="Franks&Nigel&Holldobler_1987">{{Cite journal|author-link1=Nigel R. Franks |last1= Franks |first1= Nigel R. |last2= Hölldobler |first2= Bert |doi= 10.1111/j.1095-8312.1987.tb00298.x |title= Sexual competition during colony reproduction in army ants |journal= Biological Journal of the Linnean Society |volume= 30 |issue= 3 |pages= 229–43 |year= 1987}}</ref>
<ref name="Franks&Nigel&Holldobler_1987">{{Cite journal|author-link1=Nigel R. Franks |last1= Franks |first1= Nigel R. |last2= Hölldobler |first2= Bert |doi= 10.1111/j.1095-8312.1987.tb00298.x |title= Sexual competition during colony reproduction in army ants |journal= Biological Journal of the Linnean Society |volume= 30 |issue= 3 |pages= 229–243 |year= 1987}}</ref>


<ref name="Bourke, Andrew F. G. 1995">{{cite book |last1= Bourke |first1= Andrew F. G |first2= Nigel R. |last2= Franks |title= Social Evolution in Ants |location= Princeton, NJ |publisher= [[Princeton University Press]] |year= 1995 |isbn= 978-0-691-04426-2 |oclc= 32087436 |series= Monographs in Behavior and Ecology |ref={{Harvid|Bourke & Franks|1995}}}}</ref>
<ref name="Bourke, Andrew F. G. 1995">{{cite book |last1= Bourke |first1= Andrew F. G |first2= Nigel R. |last2= Franks |title= Social Evolution in Ants |location= Princeton, NJ |publisher= [[Princeton University Press]] |year= 1995 |isbn= 978-0-691-04426-2 |oclc= 32087436 |series= Monographs in Behavior and Ecology |ref={{Harvid|Bourke & Franks|1995}}}}</ref>


<ref name="Gotwald, William H. 1982">{{cite book |last= Gotwald |first= William H., Jr. |chapter= Army Ants |pages=157–254 |chapter-url=https://books.google.com/books?id=beExVV6_i6EC&pg=PA157 |title=Social Insects |date= 2 December 2012 |volume=4|isbn= 9780323152167 }} in {{Harvnb|Hermann|1982}}</ref>
<ref name="Gotwald, William H. 1982">{{cite book |last= Gotwald |first= William H. Jr. |chapter= Army Ants |pages=157–254 |chapter-url=https://books.google.com/books?id=beExVV6_i6EC&pg=PA157 |title=Social Insects |date= 2 December 2012 |volume=4|publisher= Elsevier |isbn= 9780323152167 }} in {{Harvnb|Hermann|1982}}</ref>


<ref name="Boswell et al. 1998">{{Cite journal |last1= Boswell |first1= Graeme P. |last2= Britton |first2= Nicholas F. |last3=Franks |first3= Nigel R. |doi=10.1098/rspb.1998.0521 |title= Habitat fragmentation, percolation theory and the conservation of a keystone species |journal= Proceedings of the Royal Society B |volume= 265 |issue= 1409 |pages= 1921–25 |date=1998|pmc= 1689475 }}</ref>
<ref name="Boswell et al. 1998">{{Cite journal |last1= Boswell |first1= Graeme P. |last2= Britton |first2= Nicholas F. |last3=Franks |first3= Nigel R. |doi=10.1098/rspb.1998.0521 |title= Habitat fragmentation, percolation theory and the conservation of a keystone species |journal= Proceedings of the Royal Society B |volume= 265 |issue= 1409 |pages= 1921–1925 |date=1998|pmc= 1689475 }}</ref>


<ref name="Wrege et al. 2005">{{Cite journal |last1= Wrege |first1= Peter H. |last2= Wikelski |first2= M. |last3=Mandel |first3= J. T. |last4= Rassweiler |first4= T. |last5= Couzin |first5= I. D. |s2cid= 1704704 |title= Antbirds parasitize foraging army ants |journal= Ecology |volume= 8 |issue= 3 |pages= 555–559 |date=2005 |doi=10.1890/04-1133}}</ref>
<ref name="Wrege et al. 2005">{{Cite journal |last1= Wrege |first1= Peter H. |last2= Wikelski |first2= M. |last3=Mandel |first3= J. T. |last4= Rassweiler |first4= T. |last5= Couzin |first5= I. D. |s2cid= 1704704 |title= Antbirds parasitize foraging army ants |journal= Ecology |volume= 8 |issue= 3 |pages= 555–559 |date=2005 |doi=10.1890/04-1133|bibcode= 2005Ecol...86..555W }}</ref>


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<ref name="Schneirla, T. C. 1971">{{cite book |last1= Schneirla |first= Theodore Christian |editor-first= Howard R. |editor-last= Topoff |title= Army Ants: A Study in Social Organization |location= San Francisco |publisher= [[W. H. Freeman and Company]] |year= 1971 |isbn= 978-0-7167-0933-6 |oclc= 210501 |url-access= registration |url= https://archive.org/details/armyantsstudyins0000schn }}</ref>
<ref name="Schneirla, T. C. 1971">{{cite book |last1= Schneirla |first1= Theodore Christian |editor-first= Howard R. |editor-last= Topoff |title= Army Ants: A Study in Social Organization |location= San Francisco |publisher= [[W. H. Freeman and Company]] |year= 1971 |isbn= 978-0-7167-0933-6 |oclc= 210501 |url-access= registration |url= https://archive.org/details/armyantsstudyins0000schn }}</ref>


<ref name="Wilson&Hölldobler_2005">{{Cite journal |last1= Wilson |first1= Edward. O. |last2= Hölldobler |first2= Bert |doi= 10.1073/pnas.0505858102 |title= Eusociality: Origin and consequences| journal= Proceedings of the National Academy of Sciences |volume= 102 |issue= 38 |pages= 13367–71 |date=September 2005 |pmid= 16157878 |pmc= 1224642|bibcode= 2005PNAS..10213367W |doi-access= free }}</ref>
<ref name="Wilson&Hölldobler_2005">{{Cite journal |last1= Wilson |first1= Edward. O. |last2= Hölldobler |first2= Bert |doi= 10.1073/pnas.0505858102 |title= Eusociality: Origin and consequences| journal= Proceedings of the National Academy of Sciences |volume= 102 |issue= 38 |pages= 13367–13371 |date=September 2005 |pmid= 16157878 |pmc= 1224642|bibcode= 2005PNAS..10213367W |doi-access= free }}</ref>


<ref name="Couzin&Franks_2003">{{Cite journal |last1= Couzin |first1= Iain D. |last2= Franks |first2= Nigel R. |doi= 10.1098/rspb.2002.2210 |title= Self-organized lane formation and optimized traffic flow in army ants |journal= Proceedings of the Royal Society B: Biological Sciences |volume= 270 |issue= 1511 |pages= 139–146 |date=2003 |pmid= 12590751 |pmc= 1691225}}</ref>
<ref name="Couzin&Franks_2003">{{Cite journal |last1= Couzin |first1= Iain D. |last2= Franks |first2= Nigel R. |doi= 10.1098/rspb.2002.2210 |title= Self-organized lane formation and optimized traffic flow in army ants |journal= Proceedings of the Royal Society B: Biological Sciences |volume= 270 |issue= 1511 |pages= 139–146 |date=2003 |pmid= 12590751 |pmc= 1691225}}</ref>


<ref name="Kronauer&Johnson&Boomsma_2007">{{Cite journal |last1= Kronauer |first1= Daniel J. C. |last2= Johnson |first2= Robert A. |last3= Boomsma |first3= Jacobus J. |doi= 10.1111/j.1558-5646.2007.00040.x |title= The Evolution of multiple mating in army ants |journal= Evolution |volume= 61 |issue= 2 |pages= 413–22 |year= 2007 |pmid= 17348950|s2cid= 36371272 |doi-access= free }}</ref>
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<ref name="Schneirla_AMNH">{{cite journal |last= Schneirla |first= Theodore Christian |date=1949|title= Army-ant Life and Behavior under Dry-season Conditions. 3, The Course of Reproduction and Colony Behavior |url= http://digitallibrary.amnh.org/dspace/bitstream/handle/2246/407//v2/dspace/ingest/pdfSource/bul/B094a01.pdf?sequence=1 |journal= Bulletin of the AMNH |volume= 94 |hdl= 2246/407}}</ref>
<ref name="Schneirla_AMNH">{{cite journal |last= Schneirla |first= Theodore Christian |date=1949|title= Army-ant Life and Behavior under Dry-season Conditions. 3, The Course of Reproduction and Colony Behavior |url= http://digitallibrary.amnh.org/dspace/bitstream/handle/2246/407//v2/dspace/ingest/pdfSource/bul/B094a01.pdf?sequence=1 |journal= Bulletin of the AMNH |volume= 94 |hdl= 2246/407}}</ref>


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<ref name="Franks_ Fletcher">{{Cite journal |last1= Franks |first1= Nigel R. |last2= Fletcher |first2= Charles R. |title= Spatial Patterns in Army Ant Foraging and Migration: ''Eciton burchelli'' on Barro Colorado Island, Panama |journal= Behavioral Ecology and Sociobiology |volume= 12 |issue= 4 |pages= 261–70 |date=1983 |doi= 10.1007/BF00302894|s2cid= 30296073 }}</ref>
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<ref name="engel2005">{{cite journal |last1= Engel |first1= Michael S. |first2= David A. |last2= Grimaldi |year= 2005 |title= Primitive new ants in Cretaceous amber from Myanmar, New Jersey, and Canada (''Hymenoptera: Formicidae'') |url= http://digitallibrary.amnh.org/dspace/bitstream/handle/2246/5676/N3485.pdf?sequence=1 |journal= American Museum Novitates |issue= 3485 |pages= 1–24 |doi= 10.1206/0003-0082(2005)485[0001:PNAICA]2.0.CO;2 |hdl= 2246/5676}}</ref>
<ref name="engel2005">{{cite journal |last1= Engel |first1= Michael S. |first2= David A. |last2= Grimaldi |year= 2005 |title= Primitive new ants in Cretaceous amber from Myanmar, New Jersey, and Canada (''Hymenoptera: Formicidae'') |url= http://digitallibrary.amnh.org/dspace/bitstream/handle/2246/5676/N3485.pdf?sequence=1 |journal= American Museum Novitates |issue= 3485 |pages= 1–24 |doi= 10.1206/0003-0082(2005)485[0001:PNAICA]2.0.CO;2 |hdl= 2246/5676|s2cid= 84043939 }}</ref>


}}
}}


== Bibliography ==
=== Bibliography ===
* {{cite book |title= Social Insects |volume= IV |editor1-first= Henry R. |editor1-last= Hermann |location= New York |publisher= [[Academic Press]] |year= 1982 |isbn= 978-0-12-342204-0 |oclc= 37854847 }}
* {{cite book |title= Social Insects |volume= IV |editor1-first= Henry R. |editor1-last= Hermann |location= New York |publisher= [[Academic Press]] |year= 1982 |isbn= 978-0-12-342204-0 |oclc= 37854847 }}



Latest revision as of 14:46, 6 November 2024

African Dorylus raid

The name army ant (or legionary ant or marabunta[1]) is applied to over 200 ant species in different lineages. Because of their aggressive predatory foraging groups, known as "raids", a huge number of ants forage simultaneously over a limited area.[2]

Another shared feature is that, unlike most ant species, army ants do not construct permanent nests; an army ant colony moves almost incessantly over the time it exists. All species are members of the true ant family, Formicidae, but several groups have independently evolved the same basic behavioural and ecological syndrome. This syndrome is often referred to as "legionary behaviour", and may be an example of convergent evolution.[3][n 1]

Most New World army ants belong to the genera Cheliomyrmex, Neivamyrmex, Nomamyrmex, Labidus, and Eciton.[3] The largest genus is Neivamyrmex, which contains more than 120 species; the most predominant species is Eciton burchellii; its common name "army ant" is considered to be the archetype of the species. Most Old World army ants are divided between the tribes Aenictini and Dorylini. Aenictini contains more than 50 species of army ants in the single genus, Aenictus. However, the Dorylini contain the genus Dorylus, the most aggressive group of driver ants; 70 species are known.[citation needed]

Originally, some of the Old World and New World lineages of army ants were thought to have evolved independently, in an example of convergent evolution. In 2003, though, genetic analysis of various species suggests that several of these groups evolved from a single common ancestor, which lived approximately 100 million years ago at the time of the separation of the continents of Africa and South America, while other army ant lineages (Leptanillinae, plus members of Ponerinae, Amblyoponinae, and Myrmicinae) are still considered to represent independent evolutionary events.[3] Army ant taxonomy remains in flux, and genetic analysis will likely continue to provide more information about the relatedness of the various taxa.[4]

Morphology

[edit]
An Eciton burchellii soldier guarding workers

Workers

[edit]

The workers of army ants are usually blind or can have compound eyes that are reduced to a single lens. There are species of army ants where the worker caste may show polymorphism based on physical differences and job allocations; however, there are also species that show no polymorphism at all.[5] The worker caste is usually composed of sterile female worker ants.[6]

Soldiers

[edit]

The soldiers of army ants are larger than the workers, and they have much larger mandibles than the worker class of ants, with older soldiers possessing larger heads and stronger mandibles than the younger ones. They protect the colony, and help carry the heaviest loads of prey to the colony bivouac.

Males

[edit]

Males are large in size and have a large cylindrical abdomen, highly modified mandibles and uncommon genitalia not seen in other ants.[7] They have 13 segments on their antennae, are alated (have wings) and therefore can resemble wasps.[5] Males are born as part of a sexual brood.[7] As soon as they are born, they will fly off in search of a queen to mate with. In some instances where males seek to mate with a queen from an existing colony, the receiving workers will forcibly remove the wings in order to accommodate the large males into the colony for mating.[8] Because of their size, males are sometimes called "sausage flies" or "sausage ants."[9]

Queen

[edit]

Colonies of real army ants always have only one queen, while some other ant species can have several queens. The queen is dichthadiigyne (a blind ant with large gaster) but may sometimes possess vestigial eyes.[5] The queens of army ants are unique in that they do not have wings, have an enlarged gaster size and an extended cylindrical abdomen.[8] They are significantly larger than worker army ants and possess 10–12 segments on their antennae.[5] Queens will mate with multiple males and because of their enlarged gaster, can produce 3 to 4 million eggs a month, resulting in synchronized brood cycles and colonies composed of millions of individuals all related to a single queen.[5][10]

Behaviour

[edit]
E. vagans with larvae of a raided wasp nest
Dorylus sp. in Cameroon, consuming a grasshopper
Safari ants (Dorylus sp.) on a march in Kakamega Forest, Kenya. A column of workers moves under the protection of the soldiers, who link together into a tunnel and display their mandibles to ward off predators

Army ant syndrome

[edit]

The term "army ant syndrome" refers to behavioral and reproductive traits such as obligate collective foraging, nomadism and highly specialized queens that allow these organisms to become the most ferocious social hunters.[3]

Most ant species will send individual scouts to find food sources and later recruit others from the colony to help; however, army ants dispatch a cooperative, leaderless group of foragers to detect and overwhelm the prey at once.[3][5] Army ants do not have a permanent nest but instead form many bivouacs as they travel. The constant traveling is due to the need to hunt large amounts of prey to feed its enormous colony population.[5] Their queens are wingless and have abdomens that expand significantly during egg production.[8] This allows for the production of 3–4 million eggs every month and often results in synchronized brood cycles, thus each colony will be formed of millions of individuals that descend from a single queen. These three traits are found in all army ant species and are the defining traits of army ants.[3][11]

Nomadic and stationary phase

[edit]

Army ants have two phases of activity – a nomadic (wandering) phase and a stationary (statary) phase – that constantly cycle, and can be found throughout all army ant species.[8]

The nomadic phase begins around 10 days after the queen lays her eggs. This phase will last approximately 15 days to let the larvae develop. The ants move during the day, capturing insects, spiders, and small vertebrates to feed their brood. At dusk, they will form their nests or bivouac, which they change almost daily.[8] At the end of the nomadic phase, the larvae will spin pupal cases and no longer require food. The colony can then live in the same bivouac site for around 20 days, foraging only on approximately two-thirds of these days.[2][8] This pattern of diurnal activity does not apply to all army ants: there are also species that forage at night (nocturnal) or at both day and night (cathemeral).[12]

The stationary phase, which lasts about two to three weeks, begins when the larvae pupate. From this point on, the prey that were previously fed to the larvae are now fed exclusively to the queen.[8] The abdomen (gaster) of the queen swells significantly, and she lays her eggs. At the end of the stationary phase, both the pupae emerge from their cocoons (eclosion) and the next generation of eggs hatch so the colony has a new group of workers and larvae. After this, the ants resume the nomadic phase.[5][8]

Behaviour and organization of a bivouac

Colony fission

[edit]

Army ants will split into groups when the size of the colony has reached a size threshold, which happens approximately every three years.[13] Wingless virgin queens will hatch among a male sexual brood that hatches at a later date. When the colony fissions, there are two ways new queens are decided. A possible outcome is a new queen will stay at the original nest with a portion of the workers and the male brood while the old queen will leave with the rest of the workers and find a new nest. Another possibility is that the workers will reject the old queen and new queens will each head a newly-divided colony.[2][8] The workers will affiliate with individual queens based on the pheromone cues that are unique to each queen. When new bivouacs are formed, communication between the original colony and the new bivouacs will cease.[8]

Queen behaviour

[edit]

Being the largest ants on Earth, army ants, such as African Dorylus queens have the greatest reproductive potential among insects, with an egg-laying capacity of several million per month. Army ant queens never have to leave the protection of the colony, where they mate with foreign incoming males which disperse on nuptial flights. The exact mating behaviour of the army ant queen is still unknown, but observations seem to imply that queens may be fertilized by multiple males.[14] Due to the queen's large reproductive potential, a colony of army ants can be descended from a single queen.[10]

When the queen ant dies, there is no replacement and army ants cannot rear emergency queens. Most of the time, if the queen dies, the colony will likely die too. Queen loss can occur due to accidents during emigrations, predator attack, old age or illness.[13] However, there are possibilities to avoid colony death. When a colony loses its queen, the worker ants will usually fuse with another colony that has a queen, within a few days.[6][15] Sometimes, the workers will backtrack along the paths of prior emigrations to search for a queen that has been lost or merge with a sister colony.[15][16] By merging with a related colony, the workers would increase their overall inclusive fitness.[13] The workers that merge into a new colony may cause the colony to increase in size by 50%.

Sexual selection by workers

[edit]

Workers in army ant species have a unique role in selecting both the queen and the male mate.

When the queens emerge, the workers in the colony will form two 'systems' or arms in opposite directions. These queens that are hatched will move down either of the arms and only two queens will succeed, one for each branch. Any remaining new queens will be left in the middle and are abandoned. Two new bivouacs will be formed and break off into different directions. The workers will surround the two to-be queens to ensure they survive. These workers that surround the queens are affected by the CHC (pheromone) profile emitted by the new queen.[8]

When males hatch from their brood, they will fly off to find a mate. For males to access the queen and mate, they must run through the workers in the colony. Males that are favoured are superficially similar in size and shape to the queen. The males also produce large quantities of pheromones to pacify the worker ants.[8]

Reproduction responsibilities and problems

[edit]

In a colony, the queen is the primary individual responsible for reproduction in the colony. Analysis of genotypes have confirmed that workers are, on average, more closely related to the offspring of the queen than to that of other workers, and that workers rarely, if ever, reproduce.[17] Three factors have been suggested to rationalize the loss of worker reproduction in the presence of a queen. First, if the worker reproduces, it lowers the general performance of the colony because it is not working. Second, workers increase their inclusive fitness by policing other workers because they themselves are more related to the queen's offspring than other worker's offspring.[17] Lastly, the large male larvae become too large to be transported, forcing colonies with a sexual brood to nest for a period of 41–56 days, as compared to non-reproductive colonies that remain in the nest an average of 17 days before returning to a nomadic phase. This suggests that if workers produced male offspring, they might be hatched out of sync with the queen's sexual brood and not likely to be successfully reared to adulthood.[17]

Ant mills

[edit]

Army ants can get lost from the pheromone track while foraging, making the ants follow each other in a circular motion, potentially causing them to die of exhaustion.[18]

Foraging

[edit]

The whole colony of army ants can consume up to 500,000 prey animals each day, so can have a significant influence on the population, diversity, and behaviour of their prey.[19] The prey selection differs with the species. Underground species prey primarily on ground-dwelling arthropods and their larvae, earthworms, and occasionally also the young of vertebrates, turtle eggs, or oily seeds. A majority of the species, the "colony robbers", specialize in the offspring of other ants and wasps. Only a few species seem to have the very broad spectrum of prey seen in the raiding species. Even these species do not eat every kind of animal. Although small vertebrates that get caught in the raid will be killed, the jaws of the American Eciton are not suited to this type of prey, in contrast to the African Dorylus. These undesired prey are simply left behind and consumed by scavengers or by the flies that accompany the ant swarm. Only a few species hunt primarily on the surface of the earth; they seek their prey mainly in leaf litter and in low vegetation. About five species hunt in higher trees, where they can attack birds and their eggs, although they focus on hunting other social insects along with their eggs and larvae. Colonies of army ants are large compared to the colonies of other Formicidae. Colonies can have over 15 million workers and can transport 3000 prey (items) per hour during the raid period.[14][20]

When army ants forage, the trails that are formed can be over 20 m (66 ft) wide and over 100 m (330 ft) long.[20] They stay on the path through the use of a concentration gradient of pheromones. The concentration of pheromone is highest in the middle of the trail, splitting the trail into two distinct regions: an area with high concentration and two areas with low concentrations of pheromones. The outbound ants will occupy the outer two lanes and the returning ants will occupy the central lane.[20] The returning worker ants have also been found to emit more pheromones than those leaving the nest, causing the difference in concentration of pheromone in the trails.[21] The pheromones will allow foraging to be much more efficient by allowing the army ants to avoid their own former paths and those of their conspecifics.[19] Scaffolds structure has been observed when workers carried heavy prey food to inclined surface. Walking ants are prevented from falling by other ants.[22]

While foraging, army ants cause many invertebrates to flee from their hiding places under leaves of the forest floor, under tree bark, and other such locations, thereby allowing predators to catch them more easily. For example, in the tropical rainforests of Panama, swarms of army ants attract many species of birds to this feast of scrambling insects, spiders, scorpions, worms, and other animals. Some of these birds are named "antbirds" due to this tendency.[23] While focused on feeding on these invertebrates, birds at army-ant swarms typically allow very close approach by people – within 1–2 metres (3.3–6.6 ft) in many cases – often providing the best opportunities to see many of these species. Depending on the size of the ant swarm and the amount of prey the ants stir up, birds can number from a few to dozens of individuals. Birds that frequent army-ant swarms include the white-whiskered puffbird, rufous motmot, rufous-vented ground cuckoo, grey-cowled wood rail, plain-brown woodcreeper, northern barred woodcreeper, cocoa woodcreeper, black-striped woodcreeper, fasciated antshrike, black-crowned antshrike, spotted antbird, bicolored antbird, ocellated antbird, chestnut-backed antbird, black-faced antthrush, and gray-headed tanager.[24]

Nesting

[edit]
Eciton sp. forming a bridge

Army ants do not build a nest like most other ants. Instead, they build a living nest with their bodies, known as a bivouac. Bivouacs tend to be found in tree trunks or in burrows dug by the ants. The members of the bivouac hold onto each other's legs and so build a sort of ball, which may look unstructured to a layman's eyes, but is actually a well-organized structure.[25] The older female workers are located on the exterior; in the interior are the younger female workers. At the smallest disturbance, soldiers gather on the top surface of the bivouac, ready to defend the nest with powerful mandibles and (in the case of the Ecitoninae) stingers. Inside the nest, there are numerous passages that have 'chambers' of food, larvae, eggs, and most importantly, the queen.[26]

Symbionts

[edit]

Many species of army ants are widely considered to be keystone species[27] due to their important ecological role as arthropod predators [28] and due to their large number of vertebrate and invertebrate associates that rely on army ant colonies for nutrition or protection.[29][30][31] During their hunt, many surface-raiding army ants are accompanied by various birds, such as antbirds, thrushes, ovenbirds and wrens, which devour the insects that are flushed out by the ants, a behavior known as kleptoparasitism.[32][33] A wide variety of arthropods including staphylinid beetles, histerid beetles, spiders, silverfish, isopods, and mites also follow colonies.[34] While some guests follow the colony emigrations on foot,[35][36][31] many others are phoretically transported, for example by attaching themselves on army ant workers such as the histerid beetle Nymphister kronaueri.[37] The Neotropical army ant Eciton burchellii has an estimated 350 to 500 animal associates, the most of any one species known to science.[31]

It has been speculated that the nocturnal foraging of some army ant species is done to reduce kleptoparasitism by birds, since the bird kleptoparasites of army ants are diurnal.[12]

Taxonomy

[edit]

Historically, "army ant" in the broad sense referred to various members of five different ant subfamilies. In two of these cases, the Ponerinae and Myrmicinae, only a few species and genera exhibit legionary behavior; in the other three lineages, Ecitoninae, Dorylinae, and Leptanillinae, all of the constituent species were considered to be legionary. More recently, ant classifications now recognize an additional New World subfamily, Leptanilloidinae, which also consists of obligate legionary species, so is another group now included among the army ants.[13]

A 2003 study of thirty species (by Sean Brady of Cornell University) indicates that army ants of subfamilies Ecitoninae (South America), Dorylinae (Africa) and Aenictinae (Asia) together formed a monophyletic group, based on data from three molecular genes and one mitochondrial gene. Brady concluded that these groups are, therefore, a single lineage that evolved in the mid-Cretaceous period in Gondwana,[n 2] so these subfamilies are now generally united into a single subfamily Dorylinae, though this is still not universally recognized.[39] However, the unification of these lineages means that the only subfamily that is composed solely of legionary species is Leptanillinae, as Dorylinae contains many non-legionary genera.

Accordingly, the "army ants" as presently recognized consist of legionary species in these genera:

Subfamily Dorylinae (Aenictinae, Aenictogitoninae, Cerapachyinae, Ecitoninae and Leptanilloidinae, 2014)[40]
Subfamily Leptanillinae
Subfamily Myrmicinae
Subfamily Ponerinae
Subfamily Amblyoponinae

See also

[edit]

Notes

[edit]
  1. ^ "There are also interesting [evolutionary] convergences within the ants. Although most ant colonies live a settled existence in a fixed nest, there seems to be a successful living to be made by wandering in enormous pillaging armies. This is called the legionary habit." (Dawkins 1986)
  2. ^ "Because army ants are found almost everywhere, scientists postulated that they evolved many times after the break-up and dispersal of the supercontinent Gondwana just over 100 million years ago. The conventional view of the evolution of army ants needs a revision because of new data obtained by Sean Brady, a Cornell University, US, entomologist who has discovered that these ants evolved from a common ancestor."(Whitehouse 2003)[38]

References

[edit]
  1. ^ Dejean, Alain; Azémar, Frédéric; Roux, Olivier (2014-07-01). "An invasive ant species able to counterattack marabunta raids". Comptes Rendus Biologies. 337 (7): 474–479. doi:10.1016/j.crvi.2014.05.004. ISSN 1631-0691. PMID 25103833.
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