Ant

VI

Ant Behavior

Ants display a rich diversity of behaviors in obtaining food, promoting the survival of their colonies, and defending against predators. The various behaviors of ants are influenced by their senses and by information stored within their nervous systems. Ants seem to be capable of a certain amount of learning. For example, foraging ants rely on memory—a form of learning—to recognize landmarks in the area where they search for food.

A

Feeding

Ants feed in a variety of ways. Some hunt other insects, some collect and feed on insect corpses and other edible debris, and many cultivate certain insects that the ants “milk” to obtain a sweet liquid called honeydew. Still others collect seeds for food, and perhaps most remarkably, some ants grow and feed upon massive gardens of fungi.

In a behavior called trophallaxis, worker ants that have found liquid food outside of the nest share it with their nestmates whose work responsibilities may make them unable to leave the nest to search for food. The foraging ants store liquid food in their crop. When a hungry ant encounters a nestmate that has returned from foraging for food outside the nest, the hungry ant strokes the forager ant’s head with its antennae. The two ants then position themselves so that their mouths are touching. The forager ant forces a drop of food from its crop into its mouth and then into the mouth of the other ant. Trophallaxis enables food to flow quickly within a colony.

B

Caretaking

Worker ants provide constant care to young ants, including feeding the larvae and transporting both larvae and pupae to sites within the nest that have an optimal temperature for development. Workers constantly lick the larvae and pupae, both to clean them and to coat them with chemicals to prevent the growth of disease-causing bacteria.

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A queen ant is typically surrounded by a multitude of workers, who lick her to keep her clean and feed her through trophallaxis. Worker ants also continually lick and feed one another. Workers will carry one another on certain occasions, such as when an inexperienced worker must be transported to a new nest. All species of ants keep their nests in good repair and keep them clean by removing debris, such as empty cocoons. They place this refuse outside the nest or in a special chamber.

C

Competition and Fighting

Different species of ants that occupy the same area usually compete for food, nest sites, or space. Some species defend territories against invasion by workers from other colonies of their own species, and sometimes colonies of other species as well. Some ant species defend only their food finds and nests, while the most timid ants defend only their nests, relying on stealth, luck, and speed to get food.

Some species of ants respond to an invasion by rolling themselves into balls and remaining motionless. This response makes it hard for other ants to distinguish them from particles of soil or sand. Many ants respond more aggressively to danger. Ants commonly fight by biting each other or by gripping enemy ants while dismembering them. Some ants use their mandibles to injure an enemy and then squirt poison into the wounds.

Battles among ants may involve a huge number of individuals. Many species use trail pheromones to attract workers to the site of skirmishes. Among European wood ants, battles may last for weeks and result in thousands of dead ants each day. These huge casualties of war help the victorious colonies because battles typically occur in the spring, a time of protein shortage, and the surviving colony members eat the protein-rich dead ants.

VII

Types of Ants

Scientists recognize about 11,000 species of ants. These species display a remarkable diversity in the environments they live in, the foods they eat, and their strategies for survival. Some scientists group the many species of ants according to these survival strategies, which can be compared to certain human activities, such as harvesting, weaving, and gardening.

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