Today we are talking about the Army Ant. This species is unique because they do not for traditional colonies and forage in massive groups. The name army ant (or legionary ant or marabunta) is applied to over 200 ant species in different lineages. Due to their aggressive predatory foraging groups, known as “raids”, a huge number of ants forage simultaneously over a certain 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 behavioral and ecological syndrome.
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 behavior of their prey. 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.
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 pincers 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.
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