Ant behavior: February 2013 Archives

I'm sure you get a lot of questions phrased like my subject heading. But I'm stumped here! I've linked to two pictures I took in the woods in Atlanta, GA.

From the far shot, it looks like the ants are "herding" the insects into a big clump. in the closer shot, you can see that some ants have actually dived into the fray.

Were these ants really herding the other insects or had the insects been swarming beforehand and the ants are just there to pick some off as food?

Also, I can't seem to identify the insects in the pictures that the ants are interacting with. They look like some kind of insect in the nymph stage.

If it matters, the tree in the picture is a beech, I think.

Thanks for your help! I'm so glad I found this blog!


Dear Becky,

Thanks for the great pictures! Yes! Many ant species have facultative mutualisms with aphids (seen here) and other herbivorous insects. The ants guard the aphids from predators, and, in exchange, the aphids essentially poop sugar water into the ants mouths. This "honeydew" as it is euphemistically called, has to be voided from the aphids, because they have to go through a lot of plant sap to get enough minerals and amino acids. To the ants, it's gatorade.

The ants are most likely the common carpenter ant, Camponotus pennsylvanicus. I don't know much about aphids, but those are really big, and they seem to be on the bark of a deciduous tree, so they might be the giant bark aphids, Longistigma caryae. There're probably some other big aphids out there, but this seems to be a pretty widespread, conspicuous species, and they have been reported to associate with C. pennsylvanicus elsewhere in the Southeastern United States.

There have been a few posts about this relationship in other blogs (such as here and here ) and there's a rich scientific literature of ant-aphid mutualisms you should check out if you'd like to know more! There are also some pretty great photos that have been posted by others!

Thanks again for your great pictures!


Thanks for taking the time to answer my question. I was recently traveling in Costa Rica and happened to take a camera shot of some interesting ant behavior. I have no idea what is going on here, but would sure like to find out. Have you ever seen this kind of behavior before? (see attached image)

Please let me know.





Great image! What you have documented here, quite beautifully, is a number of Azteca workers "spread-eagling" a Pachycondyla gyne (future queen). This is an interesting and well-known behavior of the genus Azteca (Dejean et al., 2009), which is well known for its mutualistic associations with plant species (Cordia, Cecropia). The mutualism between the plants and the ants relies on the plants providing food and shelter to the ants, and the ants fervently defending the plants from herbivores and other competitive plants. This behavior, known as "spread-eagling", is usually employed by the workers to protect the plants from insect herbivores or intruders, and is not restricted to the plant alone.

Because the Pachycondyla gyne has not started her colony yet and become a queen (you can tell because she has not dropped her wings yet), it is likely that the Azteca ants are showing this aggression to defend their territory before she can start a colony and get a foothold in their area. Although the pictures don't show it, I'm guessing the gyne did not escape alive.

Hope this answers your question, I've included the reference below.


Max Winston & the AskAntTeam

Dejean, A., Grangier, J., Leroy, C., & Orivel, J. (2009) Predation and aggressiveness in host plant protection: a generalization using ants from the genus Azteca. Naturwissenschaften. 96:57-63.

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