‘Cheating’ ants punished by sisters in colony, researchers find

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01-26-09 Ants
In a recent ASU study, it was found that ants attacked females who “cheated” by including their eggs along with the queen’s progeny— not so dissimilar to human society’s concept of punishment for breaking rules. (Photo courtesy of Adrain Smith)
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Honesty is supposedly the best policy, and it’s no different for ants, an ASU research team learned.

In ant colonies, workers usually support the queen, the only female intended to reproduce, doctoral student Adrian Smith said. But now, it is apparent that that is not always the case, he said.

When a worker ant cheats the system by laying an egg of her own, the sister ants in the colony attack the cheater, Smith said.

“We identified a chemical that shows up on [the cheater’s] surface that is correlated with reproduction,” Smith said. “Then we tested it to see if other workers actually use that chemical to perceive that the individual has become reproductive, and they did.”

Smith conducted an experiment in which he painted a non-cheating ant with the same hydrocarbon, an organic compound made up of hydrogen and carbon, that corresponds with procreation, he said. Once the ant was reunited with her colony, the other workers attacked the ant, he said.

“Once other workers identify these cheaters, they attack them, and therefore prevent reproduction,” said Jürgen Liebig, an assistant life sciences professor. “Over time, you have 10 ants surrounding the cheater.”

But the bigger discovery here is that ant colonies, like many other societies, punish those who defy the rules, Smith said.

“Its like the common problem with all societies, an individual will do something that’s detrimental to the group as a whole, but to itself, it’s a gain,” he said.

Rebecca Clark, a doctoral student who also studies ants, said that she thinks this research is a significant advancement in the study of ant life.

“[Smith’s study] was a really nice demonstration that there’s no way to hide the fact that you’re cheating, if you’re cheating in an ant society,” Clark said.

The study was conducted with a species of ants native to Arizona, which makes it hit a little closer to home, Clark said.

“This stuff could be going on in your backyard without you even knowing it,” Clark said.

Although this study is a big step in the right direction, it doesn’t end here, Liebig said. The question now is how often this is happening, and to what extent

“We’re going to build on this,” Liebig said. “Adrian is already designing new experiments to further confirm these results.”

Reach the reporter at abigail.gilmore@asu.edu.