Harvester ants totally freak out over army ants

Check this out:

Arizona State University biologist Adrian Smith drops a few army ants into an Aphaenogaster harvester ant nest and mayhem ensues. Within seconds, the harvesters mass-evacuate with their queen and all the brood they can grab.

A remarkable aspect of this behavior is its predictability. Almost every colony will bail at the mere scent of an army ant. And it’s not just this species, either. I’ve seen Pheidole, Camponotus, Nylanderia, and other ants react the same way. A complete freak-out is apparently a successful strategy to counter army ant raids, and its ubiquity among target ants testifies to just how much pressure army ants place on the survival of other colonies.

16 thoughts on “Harvester ants totally freak out over army ants”

  1. Did I miss something or were the added ants about 10% the body mass of the others? A half dozen tiny ants caused those harvester ants to freak like that? Wow, I wonder what their mites are like.

    1. That first pour in the video was of about 50 army ant workers. Lamon and Topoff (1981) published a report on evacuation behavior exhibited by several Camponotus species in response to this same army ant species. They describe an even more extreme reaction:

      “Camponotus festinatus was unique in that it was the only species to exhibit nest evacuation, and in addition, contact with N. nigrescens by a single forager was sufficient to initiate this response.”

      1. Is this defense mechanism diminished in distant ant species that have likely evolved out-of-contact with the army ants? (perhaps relating to “dear enemy phenomenon”)…

  2. So is this a potential methods for non-destructively determining colony size? Add a few drops of army ant extract and aspirate everything that emerges. Seems like an intriguing idea.

  3. Is someone exploring these ants, or their smell, as an ant repellent? Of course, if everyone on the block was using army ants instead of borax or sprays, the results might not be what was expected, but it would be nice to see lawn freaks stop poisoning their ants.

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