The name army ant (or legionary ant or ''marabunta'') is applied to over 200
ant
Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22 ...
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.
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
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
.
Most
New World
The term ''New World'' is often used to mean the majority of Earth's Western Hemisphere, specifically the Americas."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: Oxford University Press, p. 3 ...
army ants belong to the genera ''
Cheliomyrmex
''Cheliomyrmex'' is a New World genus of army ants in the subfamily Dorylinae. In Central America, ''C. morosus'' is known from Mexico to Honduras, and Panama
Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es ...
'', ''
Neivamyrmex
''Neivamyrmex'' is a genus of army ants in the subfamily Dorylinae.
Range
''Neivamyrmex'' species can be found from the central United States to southern Argentina.
Taxonomy
As of 2021, 129 ''Neivamyrmex'' species have been identified. Ho ...
'', ''
Nomamyrmex
''Nomamyrmex'' is a genus of army ants in the subfamily Dorylinae. Its two species are distributed in the Neotropics: ''Nomamyrmex esenbeckii'' is known from southern United States to northern Argentina, and ''Nomamyrmex hartigii'' is known fro ...
'', ''
Labidus
''Labidus'' is a genus of New World army ants in the subfamily Dorylinae. The genus is known from the United States to Argentina.
Species
*''Labidus auropubens'' (Santschi, 1920)
*'' Labidus coecus'' (Latreille, 1802)
*''Labidus curvipes'' (Em ...
'', and ''
Eciton
''Eciton'' is a New World army ant genus that contains the most familiar species of army ants. The most predominant and well-known species is '' Eciton burchellii'', which is also more commonly known as the army ant and is considered the type spe ...
''.
The largest genus is ''Neivamyrmex'', which contains more than 120 species; the most predominant species is ''
Eciton burchellii
''Eciton burchellii'' is a species of New World army ant in the genus ''Eciton''. This species performs expansive, organized swarm raids that give it the informal name, ''Eciton'' army ant. This species displays a high degree of worker polymorp ...
''; its common name "army ant" is considered to be the archetype of the species. Most
Old World
The "Old World" is a term for Afro-Eurasia that originated in Europe , after Europeans became aware of the existence of the Americas. It is used to contrast the continents of Africa, Europe, and Asia, which were previously thought of by the ...
army ants are divided between the tribes
Aenictini and
Dorylini. Aenictini contains more than 50 species of army ants in the single genus, ''
Aenictus
''Aenictus'' is a large army ant genus distributed in the Old World tropics and subtropics. It contains about 181 species, making it one of the larger ant genera of the world.
Biology and distribution
The genus presently has 181 species, dist ...
''. However, the Dorylini contain the genus ''
Dorylus
''Dorylus'', also known as driver ants, safari ants, or siafu, is a large genus of army ants found primarily in central and east Africa, although the range also extends to southern Africa and tropical Asia. The term siafu is a loanword from Swah ...
'', the most aggressive group of driver ants; 70 species are known.
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
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
. 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.
Army ant taxonomy remains in flux, and genetic analysis will likely continue to provide more information about the relatedness of the various taxa.
Morphology
Workers
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.
The worker caste is usually composed of sterile female worker ants.
Soldiers
The soldiers of army ants are larger than the workers, and they have much larger
mandibles
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
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
Males are large in size and have a large cylindrical abdomen, highly modified mandibles and uncommon genitalia not seen in other ants.
They have 13 segments on their antennae, are
alate
Alate (Latin ''ālātus'', from ''āla'' (“wing”)) is an adjective and noun used in entomology and botany to refer to something that has wings or winglike structures.
In entomology
In entomology, "alate" usually refers to the winged form o ...
d (have wings) and therefore can resemble
wasp
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. Th ...
s.
Males are born as part of a sexual brood.
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.
Because of their size, males are sometimes called "sausage flies" or "sausage ants."
Queen
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.
The queens of army ants are unique in that they do not have wings, have an enlarged gaster size and an extended cylindrical abdomen.
They are significantly larger than worker army ants and possess 10–12 segments on their antennae.
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.
Behaviour
Army ant syndrome
The army ant syndrome refers to
behavioral
Behavior (American English) or behaviour (British English) is the range of actions and mannerisms made by individuals, organisms, systems or artificial entities in some environment. These systems can include other systems or organisms as well ...
and reproductive traits such as obligate collective foraging,
nomadism
A nomad is a member of a community without fixed habitation who regularly moves to and from the same areas. Such groups include hunter-gatherers, Nomadic pastoralism, pastoral nomads (owning livestock), tinkers and Merchant, trader nomads. In t ...
and highly specialized queens that allow these organisms to become the most ferocious social hunters.
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.
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
Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using a ...
.
Their queens are wingless and have abdomens that expand significantly during egg production.
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.
Nomadic and stationary phase
Army ants have two phases of activitya nomadic (wandering) phase and a stationary (statary) phasethat constantly cycle, and can be found throughout all army ant species.
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
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of j ...
,
spiders
Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species dive ...
, and small
vertebrates
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
to feed their brood. At dusk, they will form their nests or bivouac, which they change almost daily.
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.
Among the army ants are some species that venture out only at night, but no adequate studies of their activities have been made.
The stationary phase, which lasts about two to three weeks, begins when the
larvae
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
pupate. From this point on, the prey that were previously fed to the larvae are now fed exclusively to the queen.
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
A pupa ( la, pupa, "doll"; plural: ''pupae'') is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their ...
) 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.
Colony fission
Army ants will split into groups when the size of the colony has reached a size threshold, which happens approximately every three years.
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.
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.
Queen behaviour
Being the largest ants on Earth, army ants, such as African ''
Dorylus
''Dorylus'', also known as driver ants, safari ants, or siafu, is a large genus of army ants found primarily in central and east Africa, although the range also extends to southern Africa and tropical Asia. The term siafu is a loanword from Swah ...
'' 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.
Due to the queen's large reproductive potential, a colony of army ants can be descended from a single queen.
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.
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.
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.
By merging with a related colony, the workers would increase their overall
inclusive fitness
In evolutionary biology, inclusive fitness is one of two metrics of evolutionary success as defined by W. D. Hamilton in 1964:
* Personal fitness is the number of offspring that an individual begets (regardless of who rescues/rears/supports them ...
.
The workers that merge into a new colony may cause the colony to increase in size by 50%.
Sexual selection by workers
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
A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...
) profile emitted by the new queen.
When males hatch from their
brood
Brood may refer to:
Nature
* Brood, a collective term for offspring
* Brooding, the incubation of bird eggs by their parents
* Bee brood, the young of a beehive
* Individual broods of North American Periodical Cicadas:
** Brood X, the largest b ...
, 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.
Reproduction responsibilities and problems
In a
colony
In modern parlance, a colony is a territory subject to a form of foreign rule. Though dominated by the foreign colonizers, colonies remain separate from the administration of the original country of the colonizers, the ''metropole, metropolit ...
, 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.
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.
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.
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
Population typically refers to the number of people in a single area, whether it be a city or town, region, country, continent, or the world. Governments typically quantify the size of the resident population within their jurisdiction using a ...
, diversity, and behaviour of their prey.
The prey selection differs with the species. Underground species prey primarily on ground-dwelling
arthropods
Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...
and their
larvae
A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle.
The ...
,
earthworms
An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. Th ...
, 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
Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22,00 ...
and
wasps
A wasp is any insect of the narrow-waisted suborder Apocrita of the order Hymenoptera which is neither a bee nor an ant; this excludes the broad-waisted sawflies (Symphyta), which look somewhat like wasps, but are in a separate suborder. T ...
. 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
''Eciton'' is a New World army ant genus that contains the most familiar species of army ants. The most predominant and well-known species is '' Eciton burchellii'', which is also more commonly known as the army ant and is considered the type spe ...
'' are not suited to this type of prey, in contrast to the African ''
Dorylus
''Dorylus'', also known as driver ants, safari ants, or siafu, is a large genus of army ants found primarily in central and east Africa, although the range also extends to southern Africa and tropical Asia. The term siafu is a loanword from Swah ...
''. 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.
When army ants forage, the trails that are formed can be over wide and over long.
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.
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.
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.
Scaffolds structure has been observed when workers carried heavy prey food to inclined surface. Walking ants are prevented from falling by other ants.
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. While focused on feeding on these invertebrates, birds at army-ant swarms typically allow very close approach by peoplewithin in many casesoften 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
The white-whiskered puffbird (''Malacoptila panamensis''), also called the white-whiskered soft-wing or brown puffbird, is a near-passerine bird in the family Bucconidae, the puffbirds, nunlets, and nunbirds. It is found from southeastern Mexic ...
,
rufous motmot
The rufous motmot (''Baryphthengus martii'') is a near-passerine bird in the family Momotidae. It is found from northeastern Honduras south to western Ecuador, northern Bolivia, and western Brazil.Master, T. L. (2020). Rufous Motmot (''Barypht ...
,
rufous-vented ground cuckoo
The rufous-vented ground cuckoo (''Neomorphus geoffroyi'') is a Vulnerable species of cuckoo in the tribe Neomorphini of subfamily Crotophaginae. It is found in Bolivia, Brazil, Colombia, Costa Rica, Ecuador, Nicaragua, Panama, and Peru.HBW ...
,
grey-cowled wood rail,
plain-brown woodcreeper
The plain-brown woodcreeper (''Dendrocincla fuliginosa''), is a sub-oscine passerine bird which breeds in the tropical New World from Honduras through South America to northern Argentina, and in Trinidad and Tobago. Sometimes it is considered t ...
,
northern barred woodcreeper
The northern barred woodcreeper (''Dendrocolaptes sanctithomae'') is a species of bird in the subfamily Dendrocolaptinae. It was formerly included as a subspecies of the Amazonian barred woodcreeper (''D. certhia'').
It is found from southern Me ...
,
cocoa woodcreeper
The cocoa woodcreeper (''Xiphorhynchus susurrans'') is a passerine bird in the woodcreeper subfamily of the ovenbird family. It was formerly considered a subspecies of the buff-throated woodcreeper (''X. guttatus'').
Description
It is typicall ...
,
black-striped woodcreeper,
fasciated antshrike,
black-crowned antshrike,
spotted antbird,
bicolored antbird
The bicolored antbird (''Gymnopithys bicolor'') is a species of bird in the family Thamnophilidae. It is found in Honduras south to Panama, western Colombia and Ecuador. Its natural habitat is subtropical or tropical moist lowland forest.
It is ...
,
ocellated antbird,
chestnut-backed antbird
The chestnut-backed antbird (''Poliocrania exsul'') is a passerine bird in the antbird family. It is found in humid forests in Central and South America ( Chocó-Magdalena), ranging from eastern Nicaragua to western Ecuador. It mainly occurs in l ...
,
black-faced antthrush
The black-faced antthrush (''Formicarius analis''), is a species of passerine bird in the family Formicariidae.
Taxonomy
The black-faced antthrush was formally described in 1837 by the French naturalists Alcide d'Orbigny and Frédéric de Lafr ...
, and
gray-headed tanager.
Nesting
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.
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
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...
and (in the case of the
Aenictinae and
Ecitoninae
Ecitoninae is an ant subfamily.
They are carnivorous ants that are characterized by organizing periodic expeditions of thousands of individuals. They do not build colonies and have a constantly moving way of life. Some birds regularly follow the ...
) stingers. Inside the nest, there are numerous passages that have 'chambers' of food, larvae, eggs, and most importantly, the queen.
Symbionts
Many species of army ants are widely considered to be
keystone species
A keystone species is a species which has a disproportionately large effect on its natural environment relative to its abundance, a concept introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in maintaini ...
due to their important ecological role as arthropod predators and due to their large number of vertebrate and invertebrate associates that rely on army ant colonies for nutrition or protection.
During their hunt, many surface-raiding army ants are accompanied by various birds, such as
antbirds
The antbirds are a large passerine bird family (biology), family, Thamnophilidae, found across subtropical and tropical Central and South America, from Mexico to Argentina. There are List of antbirds, more than 230 species, known variously as an ...
,
thrushes
The thrushes are a passerine bird family, Turdidae, with a worldwide distribution. The family was once much larger before biologists reclassified the former subfamily Saxicolinae, which includes the chats and European robins, as Old World flycat ...
,
ovenbirds and
wrens
Wrens are a family of brown passerine birds in the predominantly New World family Troglodytidae. The family includes 88 species divided into 19 genera. Only the Eurasian wren occurs in the Old World, where, in Anglophone regions, it is comm ...
, which devour the insects that are flushed out by the ants, a behavior known as
kleptoparasitism
Kleptoparasitism (etymologically, parasitism by theft) is a form of feeding in which one animal deliberately takes food from another. The strategy is evolutionarily stable when stealing is less costly than direct feeding, which can mean when foo ...
.
A wide variety of arthropods including
staphylinid
The rove beetles are a family (Staphylinidae) of beetles, primarily distinguished by their short elytra (wing covers) that typically leave more than half of their abdominal segments exposed. With roughly 63,000 species in thousands of genera, the ...
beetles, histerid beetles, spiders, silverfish, isopods, and
mites
Mites are small arachnids (eight-legged arthropods). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...
also follow colonies. While some guests follow the colony emigrations on foot,
many others are phoretically transported, for example by attaching themseles on army ant workers such as the histerid beetle ''
Nymphister kronaueri''. The
Neotropical
The Neotropical realm is one of the eight biogeographic realms constituting Earth's land surface. Physically, it includes the tropical terrestrial ecoregions of the Americas and the entire South American temperate zone.
Definition
In bioge ...
army ant ''
Eciton burchellii
''Eciton burchellii'' is a species of New World army ant in the genus ''Eciton''. This species performs expansive, organized swarm raids that give it the informal name, ''Eciton'' army ant. This species displays a high degree of worker polymorp ...
'' has an estimated 350 to 500 animal associates, the most of any one species known to science.
Taxonomy
Historically, "army ant" in the broad sense referred to various members of five different ant subfamilies. In two of these cases, the
Ponerinae
Ponerinae is a subfamily of ants in the Poneromorph subfamilies group, with about 1,600 species in 47 extant genera, including ''Dinoponera gigantea'' - one of the world's largest species of ant. Mated workers have replaced the queen as the fun ...
and
Myrmicinae
Myrmicinae is a subfamily of ants, with about 140 extant genera; their distribution is cosmopolitan. The pupae lack cocoons. Some species retain a functional sting. The petioles of Myrmicinae consist of two nodes. The nests are permanent and ...
, only a few species and genera exhibit legionary behavior; in the other three lineages,
Ecitoninae
Ecitoninae is an ant subfamily.
They are carnivorous ants that are characterized by organizing periodic expeditions of thousands of individuals. They do not build colonies and have a constantly moving way of life. Some birds regularly follow the ...
,
Dorylinae
Dorylinae is an ant subfamily, with distributions in both the Old World and New World. Brady ''et al.'' (2014) synonymized the previous dorylomorph subfamilies (Aenictinae, Aenictogitoninae, Cerapachyinae, Ecitoninae, and Leptanilloidinae) unde ...
, and
Leptanillinae
Leptanillinae is a subfamily of ants. They are further divided into the tribes Anomalomyrmini and Leptanillini.
In all Leptanillini, the larvae feed their hemolymph
Hemolymph, or haemolymph, is a fluid, analogous to the blood in vertebrat ...
, 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.
A 2003 study of thirty species (by Sean Brady of
Cornell University
Cornell University is a private statutory land-grant research university based in Ithaca, New York. It is a member of the Ivy League. Founded in 1865 by Ezra Cornell and Andrew Dickson White, Cornell was founded with the intention to teach an ...
) indicates that army ants of subfamilies
Ecitoninae
Ecitoninae is an ant subfamily.
They are carnivorous ants that are characterized by organizing periodic expeditions of thousands of individuals. They do not build colonies and have a constantly moving way of life. Some birds regularly follow the ...
(South America),
Dorylinae
Dorylinae is an ant subfamily, with distributions in both the Old World and New World. Brady ''et al.'' (2014) synonymized the previous dorylomorph subfamilies (Aenictinae, Aenictogitoninae, Cerapachyinae, Ecitoninae, and Leptanilloidinae) unde ...
(Africa) and
Aenictinae (Asia) together formed a
monophyletic
In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gro ...
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
Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...
, so these subfamilies are now generally united into a single subfamily
Dorylinae
Dorylinae is an ant subfamily, with distributions in both the Old World and New World. Brady ''et al.'' (2014) synonymized the previous dorylomorph subfamilies (Aenictinae, Aenictogitoninae, Cerapachyinae, Ecitoninae, and Leptanilloidinae) unde ...
, though this is still not universally recognized.
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
Dorylinae is an ant subfamily, with distributions in both the Old World and New World. Brady ''et al.'' (2014) synonymized the previous dorylomorph subfamilies (Aenictinae, Aenictogitoninae, Cerapachyinae, Ecitoninae, and Leptanilloidinae) unde ...
(Aenictinae, Aenictogitoninae, Cerapachyinae, Ecitoninae and Leptanilloidinae, 2014)
* ''
Aenictus
''Aenictus'' is a large army ant genus distributed in the Old World tropics and subtropics. It contains about 181 species, making it one of the larger ant genera of the world.
Biology and distribution
The genus presently has 181 species, dist ...
''
* ''
Asphinctanilloides''
* ''
Cheliomyrmex
''Cheliomyrmex'' is a New World genus of army ants in the subfamily Dorylinae. In Central America, ''C. morosus'' is known from Mexico to Honduras, and Panama
Panama ( , ; es, link=no, Panamá ), officially the Republic of Panama ( es ...
''
* ''
Dorylus
''Dorylus'', also known as driver ants, safari ants, or siafu, is a large genus of army ants found primarily in central and east Africa, although the range also extends to southern Africa and tropical Asia. The term siafu is a loanword from Swah ...
''
* ''
Eciton
''Eciton'' is a New World army ant genus that contains the most familiar species of army ants. The most predominant and well-known species is '' Eciton burchellii'', which is also more commonly known as the army ant and is considered the type spe ...
''
* ''
Labidus
''Labidus'' is a genus of New World army ants in the subfamily Dorylinae. The genus is known from the United States to Argentina.
Species
*''Labidus auropubens'' (Santschi, 1920)
*'' Labidus coecus'' (Latreille, 1802)
*''Labidus curvipes'' (Em ...
''
* ''
Leptanilloides''
* ''
Neivamyrmex
''Neivamyrmex'' is a genus of army ants in the subfamily Dorylinae.
Range
''Neivamyrmex'' species can be found from the central United States to southern Argentina.
Taxonomy
As of 2021, 129 ''Neivamyrmex'' species have been identified. Ho ...
''
* ''
Nomamyrmex
''Nomamyrmex'' is a genus of army ants in the subfamily Dorylinae. Its two species are distributed in the Neotropics: ''Nomamyrmex esenbeckii'' is known from southern United States to northern Argentina, and ''Nomamyrmex hartigii'' is known fro ...
''
; Subfamily Leptanillinae:
* ''
Anomalomyrma''
* ''
Leptanilla''
* ''
Phaulomyrma''
* ''
Protanilla''
* ''
Yavnella
''Yavnella'' is a genus of ants in the subfamily Leptanillinae. Its two species are distributed in India and Israel
Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִ ...
''
; Subfamily Myrmicinae:
* ''
Pheidologeton
''Carebara'' is a genus of ants in the subfamily Myrmicinae. It is one of the largest myrmicine genera with more than 200 species distributed worldwide in the tropics and the Afrotropical region. Many of them are very tiny cryptic soil and leaf l ...
''
; Subfamily Ponerinae:
* ''
Leptogenys
''Leptogenys'' is a genus of ants in the subfamily Ponerinae. ''Leptogenys'' is the most diverse ponerine ant genus in the world; it is widespread throughout tropical and subtropical regions and there are over 260 extant species described. Mos ...
'' (some species)
* ''
Simopelta''
; Subfamily Amblyoponinae:
* ''
Onychomyrmex''
See also
* "
Leiningen Versus the Ants
"Leiningen Versus the Ants" by Carl Stephenson is a classic short story published in the December 1938 edition of '' Esquire''. It is a translation, probably by Stephenson himself, of "Leiningens Kampf mit den Ameisen" which was originally pub ...
" – fanciful 1938 short story by
Carl Stephenson about soldier ants swarming over a Brazilian plantation
Notes
References
Bibliography
*
External links
A documentary by Carl Rettenmeyer of University of Connecticut: Associates of Eciton burchelli (2009)A documentary by Carl Rettenmeyer of University of Connecticut: Astonishing Army Ants (2009)* {{commons category-inline, Army ants
Ants
Insect common names