GoKawiilIn the deserts of southeastern Arizona, a surprising scene unfolds outside the nests of small cone ants. Much larger harvester ants stand nearby with their serrated jaws open, appearing vulnerable. But instead of attacking, the smaller ants climb onto the bigger ones and begin licking and nibbling across their bodies. Scientists say this is the first known example of one ant species cleaning a much larger ant.
The behavior was reported this week in the journal Ecology and Evolution and was observed by entomologist Mark Moffett, a research associate at the Smithsonian's National Museum of Natural History. He compares the interaction to cleaner fish in the ocean that remove parasites and dead skin from larger fish, sometimes even from predators.
"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."
A Chance Observation Leads to a Discovery
Moffett, who studies the social behavior of ants and other animals, noticed the interaction while visiting a research station in Arizona's Chiricahua Mountains. One morning, as he drank coffee, he watched worker harvester ants (Pogonomyrmex barbatus) leaving their nests to gather seeds. A few of the ants caught his attention because they appeared unusually still, which is rare for these constantly moving insects.
When he zoomed in with his camera, he realized the motionless 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."
How the Cleaning Behavior Works
Over several days, Moffett observed at least 90 harvester ants interacting with the smaller cone ants, which belong to an undescribed species in the genus Dorymyrmex. He carefully documented the encounters with photographs.
The process followed a consistent pattern. A harvester ant would approach a cone ant nest and stand tall with her mandibles open (all worker ants are female). Within about a minute, a cone ant would emerge and climb onto the larger ant. In some cases, up to five cone ants would gather and begin grooming.
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