Grooming or Aggression?

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Forelius mccooki (small ants) & Pogonomyrmex desertorum
Tucson, Arizona

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.

9 thoughts on “Grooming or Aggression?”

  1. It is also not good to try and claim the “discovery” of new behaviors in a major magazine having read about them in someone’s thesis a few weeks before…but that’s a different story. Same guy, different story. I detect a theme here.

  2. In my ant research as a child I found that black ants would sometimes stumble upon little brown ants, which would attempt to bite them. The black ants were never much impressed, and would leave without really noticing the little brown ant (sometimes carrying it along for a few strides).

    Unfortunately I don’t know the species names of any of these ants. My ant taxonomy is limited to:

    carpenter ants
    black ants
    red ants
    little brown ants
    little black ants

    And added two years ago after a kitchen invasion:

    grease ants

    Notice that while grease ants share a superficial resemblance with little brown ants, they can be distinguished by their smaller size and affinity for fats and oils.

    On occasion I have observed more exotic species while on vacation, such as tiny red ants that move at light speed.

    Your blog has been inspirational and I think I’ll pull out the insect guide when I get home and try to figure out what all of these ants are really called.

  3. Ends up my insect guide is woefully deficient in ants, and the best ant database I stumbled upon on the web was found, umm, at this place called myrmecos.net. I think the black ants may be Formica argentea, although the pictures you have were taken in California I found something on the web saying they have been found in Michigan, which is at least on the right side of the continent.

    The red ants may be Formica pergandei. They were definitely slave-makers, since the red and black ants would have occasional battles and the red ants were constantly running off with black ant babies. They always seemed like ants on a mission and would make dense trails that it was bad to walk through by accident because they would sting. The black ants were much more friendly.

  4. Hey Nimravid. Michigan, you say?

    There’s a list of species here that’s slightly out of date. It might help.

    The genus Formica is extraordinarily difficult to identify to species. There are dozens of species, many of them nearly identical except for small changes in the patterns of hair (visible under the microscope) and in structures between the legs (which you need to pull the legs off in order to see). Offhand, I’d guess that your black ant is Formica subsericea, as that should be common in your area. The red-and-black ant could be many things, of which F. pergandei is one option.

  5. I actually grew up in West Virginia and live currently in Ohio.

    F. subsericea looks subtly wrong. Too much red tone in the legs?

    If there are so many species perhaps these were multiple species of ants!

    Do you know of any non-technical type of regional field guide for ants?

  6. It wouldn’t surprise me if there were multiple species you were remembering. I clearly remember counting 10-12 species of ants on my old stomping grounds as a kid; when I re-visited the site after becoming a myrmecologist I collected 36 species, many of which I’d been unable to distinguish previously.

    We’re still a ways away from having a good non-technical ant guide. For starters, the technical knowledge is not quite there yet- we’re still discovering whole new genera of ants here in North America! (Dolopomyrmex was described just last year, for instance) And to be honest, there’s probably not enough of a market for an ant guide to justify the costs of a nice, full-color book of the sort Peterson does for birds, or wildflowers.

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  8. I need help there are these little black ant in the house and in one room there are ants with light red mid bodys and black heads and butts
    Sorry for not knowing the term for these parts

    Also i kept kill the ant with glass cleaner and lysol
    any other thing like a bug bomb i could use

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