Tiny cone ants in Arizona have been seen cleaning much larger harvester ants, even inside their open jaws. The unusual behavior may benefit both species and has never been recorded before.
In the deserts of southeastern Arizona, researchers have observed an unusual interaction between two very different ants. Large harvester ants gather outside the nests of much smaller cone ants, holding their serrated jaws open. Instead of showing aggression, the smaller ants climb onto the larger ones and begin licking and nibbling their bodies, including sensitive areas. Scientists say this is the first recorded case of one ant species cleaning a much larger ant.
The behavior was detailed this week in the journal Ecology and Evolution and was documented by entomologist Mark Moffett, a research associate at the Smithsonian’s National Museum of Natural History. He likens the discovery to marine “cleaner fish” that remove parasites and debris from larger fish, even from species that could easily eat them.
“This new ant species is the insect equivalent of cleaner fish in the ocean,” Moffett said. “The potentially dangerous harvester ants even permit the visitors to groom between their open jaws.”
How the Behavior Was Discovered
Moffett, who studies the social behavior of ants and other animals, first noticed the interaction while visiting a research station in Arizona’s Chiricahua Mountains. One morning, while watching harvester ants (Pogonomyrmex barbatus) leave their nests to collect seeds, he saw something unusual. A few ants stood completely still, which is not typical for these constantly moving insects.
Looking closer with his camera, he realized those ants were covered with tiny cone ants.
“Given the usual tendencies of ants, I first assumed that I was observing aggression,” Moffett said. “But the larger ants seemed to seek the attention of the smaller ants by first visiting their nests and then allowing the small ants to lick and nibble all over them.”
Step-by-Step Ant Cleaning Behavior
Over several days, Moffett recorded at least 90 harvester ants interacting with the smaller cone ants. These cone ants belong to an undescribed species in the genus Dorymyrmex. He photographed many of the encounters to document how the process unfolds.
A harvester ant typically approaches a cone ant nest and stands upright with her mandibles open (all worker ants are female). Within about a minute, a cone ant emerges and climbs onto the larger ant. In some cases, up to five cone ants gather and begin grooming.
The interactions can last less than 15 seconds or continue for more than five minutes. During this time, the cone ants use their tongue-like mouthparts to clean the harvester ant’s body, even reaching inside the open jaws. The larger ant remains still and does not attack. When the session ends, the harvester ant shakes off the smaller ants, sometimes flipping onto her back before quickly moving away.
A Rare Example of Ant Cooperation
Moffett had never encountered anything like this in ants or other insects. The closest comparison comes from the ocean, where larger fish visit specific locations to be cleaned by smaller fish and shrimp. Similar to the cone ants, some of these marine cleaners even work inside the mouths of their hosts.
What Do the Ants Gain?
Scientists are still working to understand why this behavior occurs. Moffett suggests the cone ants may be feeding on tiny particles they remove from the harvester ants’ bodies. These could include small, energy-rich fragments, possibly from the seeds the larger ants collect. Notably, the cone ants only interacted with living harvester ants and ignored dead ones placed near their nests.
There may also be benefits for the harvester ants. While they already groom each other to remove debris, spores, and parasites, the smaller cone ants might be able to clean areas that are otherwise hard to reach. Future research could determine whether this behavior reduces infections or affects the microbiome of either species.
A Reminder to Look Closely at Nature
Moffett believes this discovery shows how much remains to be learned from observing animals in their natural environments.
“All kinds of amazing discoveries are still there to be made outside of the lab,” Moffett said. “Finding new species and behaviors in nature often requires us to pay close attention to the small things—including the ants.”
Reference: “The First Cleaner Ant? A Novel Partnership in the Arizona Desert” by Mark W. Moffett, 12 April 2026, Ecology and Evolution.
DOI: 10.1002/ece3.73308
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