thumb|upright|200px|African [[Dorylus raid]]

The name army ant (or legionary ant or marabunta) 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.

Morphology

thumb|An [[Eciton burchellii large soldier guarding smaller workers ]]

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.

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 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.

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.

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, 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 the gray-headed tanager.

Nesting

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. 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.

Symbionts

Many species of army ants are widely considered to be keystone species 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, thrushes, ovenbirds and wrens, which devour the insects that are flushed out by the ants, a behavior known as kleptoparasitism. A wide variety of arthropods including staphylinid beetles, histerid beetles, spiders, silverfish, isopods, and mites also follow colonies. While some guests follow the colony emigrations on foot, The Neotropical army ant Eciton burchellii has an estimated 350 to 500 animal associates, the most of any one species known to science. so these subfamilies are now generally united into a single subfamily Dorylinae, though this is still not universally recognized.

  • Aenictus
  • Asphinctanilloides
  • Cheliomyrmex
  • Dorylus
  • Eciton
  • Labidus
  • Leptanilloides
  • Neivamyrmex
  • Nomamyrmex

; Subfamily Leptanillinae:

  • Anomalomyrma
  • Leptanilla
  • Phaulomyrma
  • Protanilla
  • Yavnella

; Subfamily Myrmicinae:

  • Pheidologeton

; Subfamily Ponerinae:

  • Leptogenys (some species)
  • Simopelta

; Subfamily Amblyoponinae:

  • Onychomyrmex

See also

  • "Leiningen Versus the Ants" – fanciful 1938 short story by Carl Stephenson about soldier ants swarming over a Brazilian plantation

Notes

References

Bibliography

  • 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)