How Do Ants Communicate? Pheromone Trails, Touch and Sound

Pheromones: talking with chemicals

A pheromone is a chemical signal that one animal releases and another of the same species detects. Ants are the masters of chemical communication. They produce pheromones from many glands in the head, thorax, legs and abdomen, and detect them with their antennae, which are covered in smell and taste receptors.

Most ant species use somewhere between about 10 and 20 different chemical signals. Each signal has its own meaning, and the same chemical can mean different things depending on its strength. A faint whiff of alarm pheromone might make nearby ants alert, while a strong dose makes them attack.

Trail pheromones: following the scent

When a foraging ant finds food, it often heads home dragging the tip of its abdomen on the ground, leaving a thin line of trail pheromone. Nestmates follow the scent to the food, and each successful forager adds more scent on its way back.

This creates a feedback loop. Short routes get reinforced faster, because ants come back sooner and add more scent, so the colony tends to settle on the best path. When the food runs out, ants stop marking the trail, the scent evaporates, and the line disappears. Computer scientists have copied this idea in “ant colony” algorithms used to solve routing problems.

The trails of the red wood ant can stretch about 100 m (330 ft) from the mound to the trees where workers collect aphid honeydew. Over time, wood ants also learn landmarks along the way and use the sun to keep their bearings.

Alarm pheromones: raising the alarm

When an ant is attacked or crushed, it releases alarm pheromones. These spread quickly through the air and call nearby workers to the spot, where they open their jaws and prepare to fight. In wood ants, the alarm signal includes formic acid and a substance called undecane, which also act as weapons.

Some slave-making ants use “propaganda” pheromones when raiding other colonies. The chemicals confuse the defenders and make them attack each other.

Colony odor: how ants know who belongs

Every ant colony has its own scent. It comes from a mix of waxy chemicals called cuticular hydrocarbons that coat the ants’ bodies. Ants share this odor by grooming each other and exchanging food, so every nestmate smells alike.

When two ants meet, they touch antennae and check each other’s scent. A nestmate is accepted; an intruder from another colony is usually attacked. Queens also produce special pheromones that signal their presence and fertility. In many species, if the queen’s signal fades, workers start raising new queens.

Touch and food sharing

Ants are constantly touching. They tap one another with their antennae and front legs, and these taps carry information along with the chemical signals they pick up.

Many ants share liquid food mouth to mouth, a behavior called trophallaxis. Workers store food in a “social stomach”, the crop, and regurgitate droplets to nestmates and larvae. This spreads not only food but also colony odor and other chemical messages through the nest. In some ants it may even help coordinate growth and development of the young.

Some ants lead nestmates to food or a new nest site by tandem running. A leader walks slowly, and a follower keeps touching its abdomen with its antennae. If contact breaks, the leader waits.

Sound and vibration

Ants have no ears like ours, but they sense vibrations through their legs. Many species make sounds by stridulation, rubbing a ridged plate on the waist against a scraper on the abdomen.

Leafcutter ants stridulate when buried in a cave-in, and nestmates dig toward the sound to rescue them. Leafcutters also stridulate while cutting leaves, which may recruit other workers to a good leaf; their farming life is described in how do leafcutter ants grow fungus? Carpenter ants drum their heads and jaws against wood to alert the colony.

Some insects exploit these signals. The caterpillars of certain blue butterflies, such as the Alcon blue in Europe, imitate the smell and sounds of Myrmica ant queens, so the ants carry them into the nest and feed them.

How ants compare with bees

Honey bees and ants are relatives, but bees add a famous extra: the waggle dance, which tells nestmates the direction and distance to flowers. Ants have no dance language; they rely mainly on trails and touch. Read more in how do bees communicate?

Myths and facts

Myth: Ants follow a leader ant. Fact: Ant colonies have no leader. Coordinated behavior emerges from many simple chemical and touch signals passed between individuals.

Myth: The queen gives orders. Fact: The queen lays eggs and releases pheromones that affect workers, but she does not direct the colony’s work.