An Immense World: How Animal Senses Reveal the Hidden Realms Around Us

by Ed Yong

Ant pheromones are another story. There are many, and ants put them to different uses depending on their properties. Lightweight chemicals that easily rise into the air are used to summon mobs of workers that can rapidly overwhelm prey, or to raise fast-spreading alarms. Crush the head of an ant, and within seconds, nearby colony-mates will sense the aerosolized pheromones and charge into battle. Medium-weight chemicals that become airborne more slowly are used to mark trails. Workers lay these down when they find food, leading other colony-mates to foraging hotspots. As more workers arrive, the trail is strengthened. As the food runs out, the trail decays. Leafcutter ants are so sensitive to their trail pheromone that a milligram is enough to lay a path around the planet three times over. Finally, the heaviest chemicals, which barely aerosolize, are found on the surface of the ants’ bodies. Known as cuticular hydrocarbons, they act as identity badges. Ants use them to discern their own species from other kinds of ants, nestmates from other colonies, and queens from workers. Queens also use these substances to stop workers from breeding or to mark unruly subjects for punishment.