In the deserts of southeastern Arizona, an amazing scene unfolds outside the nest of a tiny stone ant. A much larger harvester ant stands nearby with its serrated jaws open, looking defenseless. But instead of attacking, the smaller ants climb on top of the larger ants and begin licking and nibbling their bodies. Scientists say this is the first known example of an ant species scavenging much larger ants.
This act was reported in this week’s magazine ecology and evolution And it was observed by entomologist Mark Moffett, a research associate at the Smithsonian National Museum of Natural History. He likens this interaction to a clean fish in the ocean, removing parasites and dead skin from larger fish, and sometimes even predators.
“This new species of ant is the insect equivalent of the ocean’s clean fish,” Moffett says. “Potentially dangerous harvest ants even allow visitors to preen between their open jaws.”
Accidental observations lead to discoveries
Moffett, who studies the social behavior of ants and other animals, noticed this interaction during a visit to a research station in Arizona’s Chiricahua Mountains. One morning, while drinking coffee, he observed worker ants (Pogonomyx barbatus) leaves the nest to collect seeds. A few ants caught his attention because they seemed unusually still, unusual for insects that are always on the move.
As I zoomed in with my camera, I noticed that the stationary ant was covered in tiny cone-shaped ants.
“Given the normal tendencies of ants, I initially thought I might be observing aggression,” Moffett said. “However, the larger ants appear to have attracted the attention of the smaller ants by first visiting their nest and then having the smaller ants lick and nibble the entire nest.”
Mechanism of cleaning operation
Over several days, Moffett observed at least 90 harvester ants interacting with smaller newt ants, which belong to an undescribed species of the same genus. Dreamy Mex. He carefully recorded the encounter with photographs.
This process followed a consistent pattern. Harvester ants approach the new ant nest and stand upright with their mandibles open (all workers are female). Within about a minute, a newt ant emerges and climbs on top of the larger ant. In some cases, up to five newt ants would gather together and begin preening.
These sessions varied in length and lasted from less than 15 seconds to more than 5 minutes. The new ant used its tongue-like mouthparts to lick the harvester’s body, reaching inside its open jaws. The big ant stayed still and did not attack. When the harvest is finished, the harvester ants shake off the small ants, but sometimes the force is so strong that they fall on their backs and immediately walk away.
Rare and unusual interactions
Moffett says he has never seen or heard of this type of behavior in ants or other insects. The closest comparison is made with marine ecosystems. There, the fish visit a “cleaning station” where parasites are removed by smaller species. Like newt ants, some of these marine scavengers also function inside the mouths of larger animals.
Possible benefits for both species
Researchers are still trying to understand what each species gains from the interaction. Moffett suggests that the newt ants feed on tiny energy-rich particles removed from the bodies of harvester ants, perhaps seed fragments collected by larger ants. Interestingly, newt ants were only interested in live ants and ignored dead specimens placed near their nests.
There may also be benefits for harvester ants. They already groom each other to remove debris, spores, and parasites, but the smaller newt ants may be able to reach hard-to-clean areas. Future studies will investigate whether this behavior reduces infections or affects the microbiome of either species.
Reminds us of nature’s hidden wonders
Moffett believes the discovery highlights how much remains unknown about animal behavior, especially in its natural environment.
“There are still all kinds of amazing discoveries to be made outside the lab,” Moffett said. “Finding new species and behaviors in nature often requires paying close attention to small things, including ants.”
