Large ants let small ants clean their jaws

We tend to think ants either cooperate inside the nest or fight their neighbors. A new study shows a third option: interspecies cleaning, which until now had been described only in marine cleaner fish. It is the first time such an observation has been made on land.

The entomologist Mark Moffett, of the National Museum of Natural History in the United States, was working at a research station in the Arizona desert. He saw large harvester ants, Pogonomyrmex barbatus, approach the nests of small ants of the genus Dorymyrmex, take up a special posture and let them clean their open jaws. The results were published in the journal Ecology and Evolution.

The numbers are impressive. The camera recorded more than 90 cleaning sessions over several days, each lasting from 15 seconds to five minutes, with one to five small ants climbing onto a single harvester. In a control experiment, the researchers offered a dead, frozen harvester: they inspected it but did not clean it, so the idea that they were eating corpses can be ruled out.

What each side gains is not yet clear. Perhaps the small ants lick nutritious lipids from the harvesters, and the harvesters gain antibacterial protection, since some Dorymyrmex secrete antifungal substances. There is also a hypothesis that the small ants pass calming pheromones to aggressive neighbors, which helps them live safely alongside them.

For anyone who keeps ants, this is a good reminder of how little we know about the everyday lives of these insects. What I liked most personally is that the conclusion rests on simple observations and careful controls.

Source: Naked Science