Army ants have a reputation for being aggressive, and their huge colonies and nomadic lifestyle make them seem very threatening.

However, while a colony of army ants, which may contain up to 20 million stinging, biting individuals, is formidable, it can advance only about one foot per minute.

Therefore, an animal can easily escape capture.

There are about 240 species of army ants, some known as legionary, or driver, ants.

Eciton burchellii, Eciton hamatum and Labidus praedator are species of army ants that live in Central and South America rainforests.

The genus Anomma is indigenous to the rainforest of Africa.

Army ants of the genus Aenktus, which are smaller, are found in Southeast Asian and African rainforests.

Army Ant Behavior

Army ants undergo cycles of activity that are linked to brood development and the reproductive activities of the queen.

The presence of young larvae stimulates the workers to form raiding parties for prey.

When larval development is complete, there is a surplus of food, which makes the workers lethargic. Some of this food is supplied to the queen for egg production and these eggs, in turn, give rise to more larvae, which again activate the workers.

Thus, there is an alternating colony behavior: a quiescent, stationary, phase and an active, exploratory, nomadic phase.

Unlike other ant species, army ants have no fixed nest.

During the active phase they forage during the day, and at night occupy temporary structures known as bivouacs, usually in holes in the ground or beneath fallen trees.

Frequently masses of worker ants form the only walls. They link their bodies together to protect the brood and queen deep within.

The nomadic phase is characterized by raids.

At dawn, the temporary bivouac becomes a seething, disorganized mass of ants, from which a raiding party develops.

Since army ants are virtually blind, they rely on odor trails for guidance.

At the advancing front, individual workers explore small areas of ground, laying down odor trails from their abdominal glands before retreating into the mass of raiders. These guide other workers, which then encounter and investigate new ground before retreating.

Behind the raiding fronts follows the rest of the colony, with the smallest workers in the middle of the column and the largest on the flanks.

Prey are carried back along the column and collected together in 'booty caches'.

New Queens

At specific times, the queen produces a special batch of eggs composed mainly of males and a few queens. A group of the workers associates with, and tends these offspring.

The new queens are the first to emerge; the later emergence of the males heralds the galvanization of the workers.

They move off in raiding parties, dividing the bivouac in two, with the old queen and her workers going off in one direction and the new queens and some workers in another.

When the splinter group bivouacs for the night, only one queen is allowed to enter it. The remaining queens are sealed out of the new colony by workers and soon die. The winged males have a pre-mating dispersal flight, after which they seek out other army ant bivouacs to find a virgin queen with which to mate.