Ants communicate largely by using chemicals called pheromones. When ants encounter members of another colony, they may fight with them.
But ants also cooperate in complex ways. They can compare potential nest sites and make decisions as a group. It’s the balance between cooperation and competition that allows ants to thrive.
In ant colonies, the queen is a reproductive female head that rules over a colony of males and workers. Her main task is to lay eggs, and she does this by cloistering herself within the nest while the rest of the ants perform various other tasks, such as gathering food, looking after the queen and her young, foraging for more food and defending the colony against intruders.
When the queen lays her first batch of eggs, she fertilises them using sperm she stored from her nuptial flight. The queen subsequently stops laying and spends the winter in her underground nest, living off her own body fat. In the spring, she begins laying again, producing her first brood of larvae.
Once the first larvae have hatched, they become the nymphs that will eventually develop into adult workers. The queen and her nymphs live together in the colony, but the nymphs are not permitted to reproduce, so they must remain with the queen until they are ready to mate. Once they are ready, the nymphs break away from the queen to start their own colonies.
Queen ant behavior consists of a strict division of labor, with specialized insects performing particular tasks such as foraging and caring for the queen and her young. When an ant queen becomes unruly, her workers may duel with each other to establish new leadership. These battles typically last for a month, but behavioral and molecular data can predict with high accuracy which ants will triumph.
The researchers studied ant behavior in three colonies of the species Indian jumping ant (Harpegnathos saltator). They found that when the colony’s queen died, the number of ants in the nest quickly declined, but the nymphs did not immediately revert to their worker role. This led the researchers to conclude that a new queen had been established by a process of social self-organization, with the nymphs taking on roles based on their behavior.
To understand the mechanism, they used tracking technology to observe ant movements in their nests, and trophallaxis to track ants exchanging food. They also monitored ants’ spatial groups, which they defined numerically on the basis of their proximity to the entrance of the nest. The data showed that when the nests were expanded, ant groups 1 and 3 became closer together, while ants in group 2 remained farther away from the entrance.
Ants live in groups called colonies and are ruled by a queen. The ants within a colony are divided into workers, drones and males, each with different functions. The workers are responsible for constructing the nest, caring for the brood and cleaning up the nest. The brood represents the next generation and is reared with great care by the workers as it is essential for a colony’s future success, both as a worker population and reproductives. The ants communicate with one another by sweeping their antennae together, through sound and through the release of odorous chemical substances called pheromones.
The pheromones released by the queen regulate sexual and social behaviour within a species, in particular, allowing the queen to modulate the primary sex ratio of her brood. This is crucial because a single queen can only lay so many eggs before she dies. A new queen must then emerge from the brood to continue the cycle.
The brood of a colony also serves as a food reserve for the adults as in the harvester ant Monomorium whitei (Chelaner whitei) and in the clonal raider ant Ooceraea biroi (Clonal). In these species, adult ants feed their larvae via a process known as trophallaxis whereby they secrete a nutrient-rich liquid from their bodies into the larvae. The larvae consume the liquid and then exude it back into their ant hosts.
Since the brood is the largest resource for a colony, it is no wonder that behaviours increasing its number with minimal investment are favoured by natural selection. Such opportunistic behaviour is seen in the form of brood theft by conspecific colonies. In laboratory conditions and in a natural habitat, ants from the primitively eusocial subfamily Ponerinae have been found to steal brood from other colonies, most often in the form of pupae. Pupae are preferred as they will directly eclose to adults without requiring further investment by the thief colony.
In order to effectively recognise and sort brood, ants must be able to discriminate between traits such as developmental stage, size, sex, caste and maternity. They are known to recognize these cues in a variety of ways, including by sorting brood into piles based on their needs. However, the exact signals that are used to distinguish brood remain largely unknown.
Ants have evolved sophisticated social structures that allow them to utilise their environment in ways not approached by other animals. Their amazing ability to cooperate and divide labour is visible in their impressive nests, known as ant hills. These mounds of earth may look random from a distance, but within each are intricate tunnels and chambers with different purposes.
Some are used for nurseries, others for food storage or as a resting place for worker ants. It is also a common home for queens and their brood, as well as a refuge from invaders. Learn more about ants on The Ant-Keeper.
As a nesting place, the ant hill is a formidable fortress, designed to keep the colony safe from predators and harsh environments. The mound is made from a combination of soil and debris, including bits of twigs and leaves, dirt, pebbles, and resin from trees (which ants use as an antibiotic). The outside is usually covered with a layer of earth mixed with some water to make it hard for intruders to burrow through. Some ant species construct low hills out of dirt while others build towering creations made from clay. In either case, the mounds are shaped to give them added strength and to help with ventilation.
Once the queen has settled in her new home, she tends to her first brood herself, feeding them from her own reserves. As her brood grows, she begins to transfer some of the work of the colony to her workers. Each ant has one specific job to carry out during their lifetime, although they can change to another activity if needed.
Often, the anthill is situated in a spot where it will be protected from animals, birds and wind. It can be hidden amongst tree roots, under stones, or inside ant stubs or logs. Some ant species even construct a long single tunnel straight down from the nest’s entrance, which can extend as far as 15 feet.
The anthill also serves as a cemetery and garbage dump. Once an ant dies, a worker carries the body to a location that is both a burial site and a trash bin.
It’s impressive to witness a long line of ants marching in unison, carrying the tiniest speck of food back to their colony. The ant’s social character is made manifest in this strong division of labor, an example of the cooperation and mutual aid that are the hallmarks of all animal life.
Each ant is assigned its role at birth, which in a few species means that an ant emerges from the pupa already labeled as a worker, soldier or queen. Its positon remains the same throughout its life, though in some dimorphic and polymorphic species, an ant may undertake different activities at various times during its lifespan.
When ants leave the nest, they mark their trail by releasing chemicals called pheromones, which others smell with their antennae. This helps to communicate a variety of messages, from “Follow me!” to “Attack the intruder!”. Ants can also communicate with one another through touch, motion and sound.
Ants aren’t the only insects that live in colonies, but they have been a model for research into how complex decentralized systems can work. In fact, cracking the code of ant colonies could lead to improvements in swarm robotics and self-healing materials.
While the ant superorganism is fascinating, individual ants are pretty smart too. Ants process information as a group, and they can compare potential nest sites before collectively choosing the best one. Solitary ants would have a harder time making this decision, and they would be more likely to make a mistake.
In addition to cooperating and helping out with the day-to-day chores of the colony, ants are able to solve difficult problems by working together. Several ant scientists have studied the way that ants react to perturbations, and they have found that older colonies are more stable than younger ones.
While most ants will not accept a fertilized egg from another queen, some will. These now-pregnant ants are known as ergatoid queens and are a key to how ant colonies can continue to grow and thrive. When a ergatoid queen is ready to begin her own colony, she will break away from the original one and head off on her own in search of a good place to start.