The Open Door Web Site
Part XXII: The Interdependence of Living Things : Social Behaviour of Animals Index
Interdependence of Living Things : Introduction
An ants' nest
A worker ant on lichen
Parasol ants, Bristol Zoo, UK
Ants with eggs
THE INTERDEPENDENCE OF LIVING THINGS
Social insects: Ants
Ants are probably the most highly developed social insects. Each colony contains at least one queen. The workers, who are all sterile females, care for the queen, enlarge, repair and defend the nest, care for the young and gather food. Some workers perform only one job throughout their lives while others may change their tasks. The soldier ants are specialized workers whose function is to guard the nest.
The nests are usually underground and are made of numerous passages and chambers. There are nurseries where the larvae develop, a Queen's chamber, store rooms and rest rooms. Some species of ant have special chambers for growing fungi. Workers are continually making new chambers.
In cold weather the developing larvae are moved further down in the nest to give them more warmth. In Europe an ants' nest may consist of 12 or more mounds of earth, each about 0,9m high, connected by underground tunnels. A nest of this size would contain millions of ants.
The ant colony is kept together by chemicals produced by the queen. These chemicals are passed between the workers in their saliva. The workers leave trails for others to follow by placing secretions from their mouths on the ground. The workers can also produce alarm chemicals. Foreign ants are identified by their odour. When two ants meet each other, they smell each other with their antennae. If both are from the same colony, one may regurgitate a drop of liquid for the other.
During a few days in the summer, large, winged ants can be seen taking to the air from the nests. The young queens are chased through the air by the males. A queen may mate with several males and she receives enough sperms to last through her lifetime: The sperms are stored in a special sac in her body. The male dies soon after mating but the queen returns to the ground. She tears off her wings and starts to build a nest. Sometimes a queen returns to the old nest to join the old queen in producing eggs.
YouTube © National Geographic: Uploaded on Apr 29, 2009
There are many different species of ants. Some species are known as slave makers. They raid the nest of other species and carry away the larvae. When the larvae change into adults they work for their captors.
Harvester ants gather seeds and store them in their nests. Parasol ants cut pieces of leaves which they take to their nest and chew into a pulp. They have special chambers in the nest where they grow a fungus on the leaf pulp. This fungus then serves as food for the ants. When the young queens fly from the nest, they carry a piece of this fungus in their jaws. They will use it when they build a new nest.
Other species of ants "milk" other insects such as aphids. Aphids have piercing mouthparts which they put into plant stems; they then suck out the plant's sap. The dairy ants stroke the aphids on the back with their antennae to make them produce a drop of sugary liquid called honeydew. The honeydew is then taken back to the nest.
The weaver ants make their nest from leaves. They hold the larvae in their jaws and gently squeeze them to make them produce silk. The ants then use this silk to join the leaves together.
The enemies of ants are other ants, spiders, frogs, toads, birds and other insects. Ants defend their nest by biting and stinging. Almost half of the ant species have a sting. The sting is a particularly good defence against other insects because it produces a poison that contains an insect repellent gas. When two ant colonies fight each other, the winners invade the nest of their opponents and carry off the larvae for food. In fact, some species of ants live in this way.
The most dangerous ant colonies are those of the army ants and the driver ants which are found in tropical forests. These species of ants do not have a permanent nest. They move through the tropical forests, eating as they go. The soldier ants, with their large, vicious jaws, guard the rest of the colony. At night the whole colony rests in the hollow of a tree. The queen and the larvae are in the centre, protected by a mass of workers' bodies.
The army ants eat all the arthropods which are unlucky enough to be in their path. The driver ants, however, will kill and eat anything, even a cow or a goat if it is tied and cannot get away. There can be up to 22 million individuals in a colony of driver ants.
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