These European paper wasps (Polistes dominula) are having what might be the grossest conversation ever: They’re communicating by exchanging vomit! This process is called trophallaxis. Some animals perform this behavior to pass along nutrients. For instance, a mother penguin regurgitates, or vomits up, food to feed her chick. But for many species of insects, including ants, bees, termites, and wasps, trophallaxis isn’t just about sharing nourishment—it’s also about trading information.
A few years ago, a team of scientists at the University of Fribourg in Switzerland analyzed ant vomit. They found that it contained long waxy molecules called recognition cues. Insects use these molecules to identify other colony members. The puke also helps teach other colony members how to find food. By eating the half-digested gunk, they’re able to piece together what good food is supposed to smell and taste like so they can track down more of it.
Trophallaxis isn’t the only way insects communicate. Many transfer information through chemical messengers, called pheromones, released into the air from their bodies. One whiff of these chemicals can provide information about potential mates, predators, or the location of food. But communicating with puke has one advantage over broadcasting a smell—it’s private. “Pheromones are a bit more like Twitter,” says Adria LeBoeuf, who led the team that discovered the insects’ nauseating communication style. “When you post something, anybody can see it. Trophallaxis is more like text messaging just to your friend.”