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 their colonies 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.
Army ant colonies travel about as a whole colony looking for prey.
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!
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 from predators.
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 and pupae 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.
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 antennae help
them feel their surroundings and detect the chemical trails.
Due to their large colony size (up to 1 million
ants) and carnivorous habits,
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.
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.