Ants live in colonies, which are big groups of ants that live together, with some colonies holding thousands to millions of individual ants, and within a colony the queen is the ant that lays the eggs, while almost all the ants that people see are female workers that cannot lay eggs. Workers find food, take care of the young, and build and defend the nest, and they groom and carry the young inside it. Cooperation in ant colonies is largely self-organized, meaning that coordination arises from interactions among individual ants.

Ants communicate by passing messages with smells, touch and vibrations, and in 1959 E. O. Wilson and mathematician William Bossert discovered how ants communicate with chemical signals called pheromones, which ants use to warn each other of danger or to lead each other to food. If an ant colony is attacked, ants make alarm chemicals that call other workers to help defend the nest, and when an ant finds food, it lays a scent trail on the way home, which makes other ants likely to follow the same path.

Deneubourg's team provided Argentine ants with a bridge that had two branches between the nest and the food, one of them twice as long as the other, and within a few minutes the colony usually chose the shorter branch. The first ants back at the nest were those that took the shorter path both ways, and that route was marked with pheromone twice first, so nestmates were drawn to it. Simple interactions, such as one ant following another's trail, can together solve hard problems like finding the shortest route to food.

The Gordon lab at Stanford studies ant colonies as systems that work without central control, comparing them to the internet, the immune system and the brain, and an ant colony can act like one living thing, a superorganism, because its members communicate and cooperate. Engineers have borrowed this principle, building a routing technique in which antlike agents deposit bits of information at network nodes to strengthen good paths, while computer scientists copy ants' pheromone trails but add pheromone decay. When the chemical evaporates quickly, longer paths have trouble keeping stable trails, so software ants can find a shorter route even if it is found late.

All ants live in advanced societies with cooperative parenting and division of labor, although their ancestors were solitary wasps, and as of November 2026 the oldest certifiable ant fossils include Gerontoformica cretacica, which was found in Lower Cretaceous amber from France. As of November 2026, an ant caught hunting in amber is believed to be 99 million years old, and a fossil worker ant in New Jersey amber, some 90 million years old, showed that ant diversification began earlier than scientists had thought. Fossil evidence also suggests that the earliest ants lived in very small colonies of a few dozen nestmates.

Weaver ants build their nests by pulling leaves together, and workers form chains to do it. A larva is a baby ant that has no legs and looks like a soft white worm, and weaver ant workers use their own larvae like needles: the larvae make silk that stitches leaves together to form the nest. Ants grab the leaf edge, nestmates grab the first ant's body, and the chain together drags and bends the leaf, and the chance that others will join grows once one ant or group is already pulling, which is an example of positive feedback.

In their native Argentina, Argentine ant colonies stay small, and workers clash with neighbors of the same species, yet in Europe a supercolony of Argentine ants stretches over more than 3,700 miles, which was the largest cooperative unit ever recorded as of the 2002 report. Ants from the same Argentine ant supercolony do not fight each other, even when they come from different nests, and Argentine ants in Europe may have formed supercolonies by genetic cleansing, in which genetically similar colonies cooperated, wasted less time fighting and did better than the others. The yellow crazy ant can also form supercolonies that house hundreds or even thousands of queens.

Leafcutter ants carry leaf pieces to their nest and use them to grow a fungus garden, and the Texas leafcutter ant is one of only three leafcutter ant species found in the United States, with a nest that can cover more than half an acre, marked by many crater-shaped mounds. These ants arrived in the region about 10,000 years ago, after the glaciers retreated at the end of the last Ice Age. They farm a fungus that evolved to tolerate cold Texas winters, which lets them keep winter gardens, although the fungus is still cold-sensitive enough to limit how far north the ants can spread.

When a flood comes, fire ants cling together and float in a group, and a fire ant raft carries the whole colony, with the queen and young in the middle. A raft builds itself in less than 100 seconds, and it heals itself: if one ant is removed, others move in to fill the gap. Fire ants in water grip each other with a force 400 times their body weight, making the raft act like a thick, stretchy fluid made of ant molecules, and as of November 2026, Georgia Tech scientists found that it takes exactly 10 ants to form a stable raft, with each fire ant connecting to an average of 14 others to form a water-repelling seal.

Ants range in size from tiny to about an inch long, and they have strong jaws called mandibles that they use to carry things and to cut. Some ants can sting, although all ants can bite, and a fire ant sting can cause burning, itching and swelling. Trouble breathing or a tight chest after a sting means getting medical help right away, so if an ant stings or bites you, tell a grown-up, and to stay safe from fire ants, stay away from their mounds and from floating rafts of ants.

As of November 2026, scientists have named more than 12,000 kinds of ants, and about 20 quadrillion ants live on Earth, which works out to about 2.5 million ants for every person. A Texas leafcutter ant colony can hold up to about 2 million ants. As of November 2026, researchers estimate that the world's ants hold about 12 megatons of carbon, more than all wild birds and mammals combined, and as of November 2026, one survey in the Brazilian Amazon found that the biomass of ants is about four times that of all land vertebrates combined.

Words to know

• pheromones: scent chemicals
• superorganism: one living thing
• supercolony: giant ant group
• fungus: mushroom-like living thing