Forelius mccooki (small ants) & Pogonomyrmex desertorum
In last August’s National Geographic, photographer Mark Moffett has a controversial photo essay depicting a large, motionless harvester ant being worked over by smaller Dorymyrmex workers. Moffett’s interpretation of the behavior is this:
While observing seed-harvester ants on the desert flats west of Portal, Arizona, I noticed workers would approach a nest of a tiny, unnamed species of the genus Dorymyrmex. A harvester would rise up on her legs with abdomen lifted and jaws agape, seemingly frozen in place. Soon one or more of the little Dorymyrmex would climb aboard, licking the harvester here and there. This odd ant cleaning behavior brings to mind the interaction between some reef fish and typically smaller “cleaner fish”.
Cleaner ants are an amazing hypothesis, if true. However, most myrmecologists with whom I’ve discussed the behavior are skeptical. For starters, no one has done the experimental work required to test the hypothesis. To have an idea, attractive though it may be, splashed about on the pages of a major magazine without first undergoing any sort of rigorous evaluation rubs scientists the wrong way. After all, National Geographic has been burned by fraud in the past. And then, the “cleaner ants” in some of the photos look like they are biting pretty hard, more in line with ordinary defensive behavior.
Regardless of what it means, these harvester ant/dolichoderine interactions are striking. I’ve seen it a few times myself, with Pogonomyrmex barbatus and Dorymyrmex near Portal, and here in Tucson with P. desertorum and Forelius mccooki (shown in the photograph at the top). The harvester ants freeze up when they bump into a foraging trail or nest entrance of the smaller dolichoderines, and the smaller ants swarm up over them until the large ant eventually wanders away. Someone really ought to give the behavior a proper study.