Ant communication is accomplished primarily through chemicals called pheromones. Because most ants spend their time in direct contact with the ground, these chemical messages are more developed than in other Hymenopterans. So for instance, when a forager finds food, she will leave a pheromone trail along the ground on her way home. Home is typically located through the use of remembered landmarks and the position of the sun as detected with compound eyes and also by means of special sky polarization-detecting fibers within the eyes.

In a short time other ants will follow this pheromone trail. Returning home, they reinforce this same trail which in turn attracts more ants until the food is exhausted, after which the trail is no longer reinforced and so slowly dissipates.

This elementary behavior explains how ants adapt to changes in their environment. When an established path to a food source is blocked by a new obstacle, the foragers leave the path to explore new routes. If successful, the returning ant leaves a new trail marking the shortest route. Since each ant prefers to follow a path richer in pheromone rather than poorer, the resulting route is also the shortest available.

Ants make use of pheromones for other purposes as well. A crushed ant, for example, will emit an alarm pheromone which in high concentration sends nearby ants into an attack frenzy; and in lower concentration, merely attracts them. To confuse their enemies, several ant species even use what are termed propaganda pheromones.

Like other insects, ants smell with their antennae, which are long and thin. These are fairly mobile, having a distinct elbow joint after an elongated first segment; and since they come in pairs--rather like binocular vision or stereophonic sound equipment--they provide information about direction as well as intensity. Pheromones are also exchanged as compounds mixed with food and passed in trophallaxis, giving the ants information about one another's health and nutrition. Ants can also detect what task group (e.g. foraging or nest maintenance) to which other ants belong. Of special note, the queen produces a certain pheromone without which the workers would begin raising new queens.

Ants attack and defend themselves by biting and in many species, stinging, often injecting chemicals like formic acid.

While many types of animals can learn behaviors by imitating other animals, ants may be the only group of animals besides primates and some other mammals in which interactive teaching behavior has been observed. Knowledgeable forager ants of the species Temnothorax albipennis directly lead naive nest-mates to newly discovered food sources by the excruciatingly slow (and time-costly) process of "tandem running". The follower thereby obtains knowledge that it would not have, had it not been tutored, and this is at the expense of its nest-mate teacher. Both leader and follower are acutely sensitive to the progress of their partner. For example, the leader slows down when the follower lags too far behind, and speeds up when the follower gets too close, while the follower does the opposite (Franks and Richardson, 2006).

Ants usually lose, or never develop, their wings. Therefore, unlike their wasp ancestors, most ants travel by walking. Some tend to develop literal paths--the tiny equivalent of deer trails--or create unseen paths using chemical hints (Pheromones) left for others to smell.

The more cooperative species of ants sometimes form chains to bridge gaps, whether that be over water, underground, or through spaces in arboreal paths.

Among their reproductive members, most species of ant do retain wings beyond their mating flight; most females remove their own wings when returning to the ground to lay eggs, while the males almost invariably die after that maiden flight.

Some ants are even capable of leaping. A particularly notable species is Jerdon's Jumping ant (Harpegnathos saltator).

There is a great diversity among ants and their behaviors. They range in size from 2 to about 25 millimetres (about 0.08 to 1 inch). Their color may vary; most are red or black, but other colors can also be seen, including some tropical groups with a metallic lustre.

See list of ant genera (alphabetical) for an alphabetical compendium of worldwide ant genera, and antbase.org/Hymenoptera Name Serverfor a complete catalogue of all the currently known ant species of the world and their synonyms.
Antbase.org/Hymenoptera Name Server is providing an up to date record of the actual number of species, and allows to follow the description of new taxa.

Of special note:

Bullet Ants (Genus Paraponera), located in Central and South America, are the most venomous insect. Stings are incredibly painful, though usually non-fatal.

Jack jumper ants, (Myrmecia pilosula) located in Australia, are quite deadly to a small number of people in the population, and cause hospitalizations each year.

The Masai of Africa had an abiding respect for the Siafu Ants, voracious predators that consume a large amount of insects and are welcomed for the benefit they bring to farmers, as they will eliminate all pests from a crop and quickly move on.

Some of the more advanced ants are the army ants and driver ants, from South America and Africa respectively. Unlike most species which have permanent nests, army and driver ants do not form permanent nests, but instead alternate between nomadic stages and stages where the workers form a temporary nest (bivouac) out of their own bodies. Colonies reproduce either through nuptial flights as described above, or by fission, where a group of workers simply dig a new hole and raise new queens. Colony members are distinguished by smell, and other intruders are usually attacked, with notable exceptions.

Some ants will raid the colonies of other ants, taking the pupae with them, which once hatched act as workers in the raider's colonies despite not being genetically related to the queen. A few species, such as the Amazon ants (e.g. Polyergus rufescens), have become utterly dependent on such slaves, to the point of being otherwise unable to feed themselves.

Some ants, called honeypot ants, have special workers called repletes who simply store food for the rest of the colony, generally becoming immobile with greatly enlarged abdomens. In hot, dry places, even deserts, in Africa, North America and Australia where they live, they are considered a great delicacy.

Weaver ants (Oecophylla) build nests in trees by attaching leaves together, first pulling them together with bridges of workers and then sewing them together by pressing silk-producing larvae against them in alternation.

Leafcutter ants (Atta and Acromyrmex) feed exclusively on a special fungus that lives only within their colonies. They continually collect leaves which they cut into tiny pieces for the fungus to grow on. These ants have several differently sized castes especially for cutting up the pieces they are supplied with into even smaller pieces. Leaf cutter ants are sensitive enough to adapt to the fungi's reaction to different plant material, apparently detecting chemical signals from the fungus. If a particular type of leaf is toxic to the fungus the colony will no longer collect it. The ants grow the fungus because it produces special structures called gongylidia which are fed on by the ants. They create antibiotics on their skin, and subsist entirely on this farming of the fungus.

Fire ants are unique by having a poison sac where the contents consists largely of piperidine alkaloids.

Silver ants navigate by using their eyes instead of pheromones to find their way back home.

Scientists recently discovered that Sahara desert ants have an internal pedometer that keeps tracks of how many steps they take, and use it to find their way back to the nest. *

Some ants are equipped with mandibles called trap-jaws. This snap-jaw mechanism, or catapult mechanism, is possible because energy is stored in the large closing muscles. The blow is incredibly fast, about 0.5 ms in the genus Mystrium. Before the strike, the mandibles open wide and are locked in the open position by the labrum, which functions as a latch. The attack is triggered by stimulation of sensory hairs at the side of the mandibles. The mandibles are also able to function as a tool for more finely adjusted tasks. Two similar groups are Odontomachus and Dacetini - examples of convergent evolution.

Australian green ants are eaten by the aboriginals. Their abdomens taste like lemon sherbet, are high in vitamin C and have antibiotic properties. Squashed green ants mashed in water makes up an excellent lemon-lime flavored drink. The Amazon is also said to have lemon ants.*

The Australian bulldog ant Myrmecia pilosula has only a single pair of chromosomes. Males have just one chromosome since they, like all male Hymenopterans, are haploid. The Australian bulldog ants are also among the biggest and most primitive. Each individual hunts alone, using its large eyes instead of their chemical senses to find prey. Like all ants they are social, but their social behavior is poorly developed compared to more advanced species.

Scientists recently discovered that Polyrhachis sokolova, a species of ant, can swim and live underwater.