Science: How to tease your fellow ants

What happens when your species of ants likes to eat exactly the same things, in the same area as another species of ants? Well…you basically have two options:

1) be better than your opponent at finding/exploiting this food
2) mess with your opponent, so they can’t go out and find the food

It appears that one species of ant, Conomyrma bicolor has taken to vastly preferring the second option! These ants live together in the rangeland of Arizona with other ants (mostly Myrmecocystus). The problem is that these ants like the same food..and they’re not willing to share!

In order to make sure that Conomyrma gets enough food, every day they send some of their ants to the Myrmecocystus colonies. Here, they start picking up stones and throwing them in the nest entrance of the poor Myrmecocystus the entire day.

Conomyrma dropping stones in the nest entrance of Myrmecocystus (Drawing by Turid H

Conomyrma dropping stones in the nest entrance of Myrmecocystus (Drawing by Turid Hölldobler, copyright Springer Verlag)

 This prevents them from going out to work for several reasons, not all of which are clear. They of course have to spend some time cleaning up the stones, but when a human experimenter started throwing in stones, the ants didn’t care much and just started looking for food instead. The Conomyrma ants might put a chemical on the stones that tells the other ants: ‘Hey…we’re up here, you better stay in your colony or you’ll be sorry!’.

This behaviour prevents the Myrmecocystus from foraging for long periods of time. How do they survive this? Well, in the second part of August, the Conomyrma stop teasing the Myrmecocystus. During this time they might have enough time to build up enough food-stores in order to survive periods where the ‘teasing’ is high. Remember my last blog post about Myrmecocystus? The repletes I talked about might facilitate this, giving the ants food storage containers during times of famine.

And so, it all comes together!

Möglich, M.H.J. & Alpert, G. (1979). Stone dropping by Conomyrma bicolor (Hymenoptera: Formicidae): A new technique of interference competition. Behavioral Ecology & Sociobiology 6, 105-113

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2 Responses to Science: How to tease your fellow ants

  1. hannele says:

    Very interesting! Do you know if they’ve tested to see how ant-thrown stones differ from human-thrown ones, did they actually check if it was some secretion that had the effect?

  2. antyscience says:

    The authors suggest that chemical alteration is highly unlikely. They discuss that it’s more likely that it acts as a kind of extra mechanical signal. Stones don’t refrain ants from coming out, but the ants together with the dropping of stones does. I cite from the paper: ‘[we hypothesize that] in C. bicolor the stone dropping assumes a signal function to reduce the necessity of chemical display and the number of workers needed.”

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