Army Ants

Army Ants

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hymenoptera
Family: Formicidae
Subfamily: Dorylinae (meaning "spear" in Greek)
Genus: Eciton
Species: Eciton burchelli

They are found mostly in the tropical and sub-tropical regions of Central and South America. A related species, mostly known as Driver Ants, are found in Africa, south-east Asia and Australia.

These ants travel in colonies, consisting of the queen, the queen’s brood (her eggs), soldiers, and the workers. Each colony can number as large as one million ants (20 million for the Driver Ants!). They make temporary nests as they travel. These nests are called bivouacs, and are made of the actual ants themselves. They hang from a surface (log, low branch, etc), fastened to each other's bodies using their powerful mandibles (jaws) and claws. The living walls enclose the queen and her brood. Tunnels exist in the bivouac, where prey is moved by the walls of ants to different chambers in the nest.

Army ants are so called as a result of their foraging behaviours. They have two phases: nomadic and stationary. When the area they have been hunting lately has been exhausted of food, the ants go into nomadic mode. This last for about 17 days. During this time, the ants move at night and camp during the day. They travel from area to area in a 10 to 20 meter wide river, looking for a new hunting area they have not been to lately.

The stationary phase lasts between 14 and 20 days. During their stationary phase, the ants keep a bivouac as a headquarters, from which they emerge every dawn to hunt. They take a new direction almost every day, systematically hunting out the ground for 350 meters around them. The direction of their raids changes an average 123 degrees after every day. The form of their movement looks like a thick wave in front, with much thinner streams of ants behind that converge into a thin line leading back to the bivouac. It is called a "swarm raid." The first wave of ants overcomes all animals and insects with stingers, claws and the mandibles, and then cuts the prey into smaller pieces, and sends those back to the bivouac on the smaller streams of ants behind the vanguard. Animals regularly killed by army ants include lizards, snakes, scorpions and insects of all types. However, the ants will kill chickens, pigs, and goats if the animals cannot get away in time. The ants even travel into trees to kill arboreal insects and birds. Stories have been reported of farmers who lost small herds of cattle that were penned in a barn or fence when the ants came through. Army ants kill and eat up to 100,000 prey per day.

As a result of their expert navigation (though most of the ants are blind) and their ability to keep the temperature of the inside of a bivouac constant to within one degree, army ants are thought by some scientists to have a collective conciousness.