Always on the Move
Army ants are active, aggressive insects who live in temporary nests that they make by linking together their own bodies! They move theircolonies regularly in search of prey that may include everything from insects to small mammals. There are about 150 species of army ant. They are found mostly in the warm tropical and subtropical regions of the Neotropics in South and Central America. In Africa, similar types of ants – driver ants – are also sometimes called army ants.
Special adaptations to their on-the-move lifestyle make army ants fascinating to study. Like all ants, their mouths have two scissor-like jaws called mandibles. The mandibles are not for eating. They are for crushing, cutting, and biting. Army ants can only swallow liquids.
Carrying Out Duties
Army ant soldiers are the workers who capture and cut up prey. This unlucky 5cm-long whip spider was captured and cut into pieces the ants could carry. It took them less than 10 minutes!©G.Ellis/GLOBIO.org
An army ant community is divided into three groups: a queen, drones (males), and workers (females). There are several different kinds of workers. Each type has a different kind of mandible. The giant mandibles of the guard army ants protect the smaller workers frompredators. The medium-sized mandibles belong to the soldier army ants. Their main job is to capture prey, cut it up, and deliver it to the colony.
The Nest: It’s Alive!
Army ants create a temporary nest out of their own bodies. Individual ants fasten onto each other using hooks and spines on their feet and their mandibles. In this way, the ants form a living nest, complete with walls and tunnels. These living nests are called bivouacs. Inside the bivouac, the queen and her eggs and developing larvae andpupae are safe from weather and predators. Workers bring prey inside the bivouac. They may also move the eggs to different parts of the bivouac.
Blind as an Ant?
Army ants are great hunters. They use their large, strong mandibles to tear apart their prey.©G.Ellis/GLOBIO.org
Unlike other ants, army ants do not have compound eyes. Only the queen and the males have single eyes. The workers are all blind and rely on chemical trails to find their way around and to get to and from their colony’s nest. Their antennaehelp them feel their surroundings and detect the chemical trails.
Due to their large colony size (up to 1 million ants) and carnivoroushabits, army ants are nomads who must migrate in order to find enough food. Raids begin when they locate prey such as the ants in another ant nest. Then the attack begins.
A Swarm or a Raid?
Army ant guard workers have huge mandibles that they use for defending the other members of the colony.©G.Ellis/GLOBIO.org
Different species of army ants have different techniques for attacking. Some species are swarm front attackers. A swarm front attack looks like a giant wave that sweeps into an area and over everything in its path. A raid front attack consists of small groups of ants coming from different directions and attacking. In each case, ants move back and forth along chemical trails they create as they move. Giant guard ants with huge mandibles line the trail and watch over the workers and protect them.
Army ants can kill and eat up to 100,000 animals in a day. Most of these animals are arthropods such as insects and spiders. Working as a team, army ants can also kill larger animals such as lizards, snakes, chickens, and small mammals. They also climb trees and attack birds in nests.
Follow Those Ants!
The sight of an army ant colony on the move can be pretty scary! All the small animals in the colony’s path start to panic and try to escape. As they hop, fly, and run to avoid the army ants, they open themselves up to attack by other predators. Troops of monkeys and birds may spot them. For this reason, these predators often follow a migrating army ant colony and catch arthropods and small animals as they try to escape. Symbiosis of this kind is called commensalism.