While the effect that pheromones have on humans is still largely a mystery, scientists have managed to observe and study the effects of them in many other species, and sometimes those pheromones can act as very powerful social signals that control behavior, communication, sexuality, and more.
One of the most startling examples of pheromones at work in nature, and one that displays the immense influence they can have, is a phenomenon that army ants sometimes find themselves in called an ant mill.
Known for their ferocity, army ants hunt for not only insects and spiders, but also larger animals such as birds. Many army ants, however, are completely blind and use pheromones from other ants for guidance. According to pheromone expert Bruce Boyd, “modern animal and insect species have a somewhat more specialized pheromone system, where secretory glands and receptor systems have evolved.”
If enough ants lose this pheromone trail, they start to follow the ant directly in front in a circular pattern. It is one of the most bizarre sights in nature, ants continuing to follow this trail until they die from exhaustion, illustrating just how powerful pheromones can be. These ant mills are usually small, but one was measured at over 1,200 feet in circumference by biologist William Beebe in 1921. In this giant ant mill, a single rotation took two and a half hours.
According to Beebe, the ant mill lasted for two days, “with ever increasing numbers of dead bodies littering the route as exhaustion took its tool but eventually a few workers straggled from the trail thus breaking the cycle, and the raid marched off into the forest.” However, if nothing disrupts the spiral, the ants will continue marching until their demise.
It’s possible to create an ant mill on your own by diverting a few ants into a closed off space, but we obviously don’t recommend that! Once they start circling, they will literally continue until they drop dead.