Ants may be small but they are one of the most numerous and successful families of animals on the earth. They are also widespread, occuring in practically every terrestrial ecosystem, although they are most common in the tropics. They are insects, so they have six legs and three body parts: head, thorax, abdomen. The segments between the thorax and abdomen are small, giving ants a characteristic 'wasp-waist'. Ants also have short, 'elbowed' antennae and biting mouthparts (mandibles).
Ants belong to the order Hymenoptera, which means membranous-winged, along with the wasps and bees. They are grouped in the family Formicidae, which refers to another ant characteristic: the production of formic acid, used to deter predators and make ants taste bad. They can also bite and sting to protect themselves and their colony. Ants are mostly vegetarian but there are some carnivorous forms. There are some that feed on fungi and others that prefer tree sap or the nectar of flowers. Many are scavengers. Within a colony some of the individuals are fed by other members. In total, there are more than 8000 species of ants, with numerous lifestyles, behaviours and eating habits; but all are social and live in colonies.
Most ants are wingless, with only queens and males able to fly. Once the female mates and sets up a new colony, she loses her wings. The males are short-lived, dying soon after mating. The female stores sperm and so is able to fertilise her eggs throughout her lifespan without mating again. Her children are mostly sterile, wingless females who are the workers of the colony. Some colonies contain only a few individuals, while others number in the millions. Ant nests are found in many different habitats. The most common habitat is under the ground but they can also be found inside trees and shrubs or even in the walls of buildings.
The carnivorous ants or meat ants are the most aggressive. In Australia the meat ants are large, with big biting mandibles. I have left a dead echidna on a nest and had it stripped to the bones and quills within a few days. They are strong and able to drag big hunks of meat back to the colony. But the most aggressive ants are the feared army ants of South America. These ants march together on foraging expeditions and in the process, all living things in their path are in danger, There are about two hundred species of army ants.
Ants are not just mindless automatons. They can respond to changes in their environment and conditions in their nests. When they go out foraging, they leave pheromone trails which can be followed by other ants and they can communicate food sources to other members of their colony, sometimes by tapping on each others' antennae. The most important aspect of ant behaviour is that they act for the good of the community without thought for their own safety. They will forage in dangerous territory in order to supply food to the colony and they will defend their colony to the death. They are fiercely protective of their territory and if a strange ant comes in, it will be killed. An ant separated from its colony is a dead ant for it loses its will to live and its purpose in life.
It may seem a strange way to live, especially for humans where the individual is so important, but the ant's strategy is highly successful. It is an example of kin selection. Since every ant in a colony is related, to sacrifice one's life for the colony means that one's genes will go on, even if the individual does not. This is especially true for ants since the workers are sterile anyway. If the queen dies, then their colony and their genes will be lost, so in this case, it is better to die fighting than to run and hide and die anyway.