First Rule of the Ant Colony: No Hanky-Panky

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Jason Edwards / National Geographic / Getty

To the long list of reasons you should be glad you're not an ant, add this: You'd have to forget about having sex. You'd also have to forget about even trying. Sneak off for a little insectile assignation and the other members of the colony would know immediately — and attack you for it. Entomologists have long known this was the practice in the ant world, but what they didn't know is the forensic science that allows the community to uncover the crime. Now, thanks to a study in the current issue of Cell Biology, they do.

Ant colonies have good reason to be abstemious places. When you're trying to hold together so complex a society without — let's face it — a lot of brainpower, you want a population made up of the fittest individuals you can get. A queen that has the genetic mettle to crank out lots of good eggs that produce lots of good babies doesn't need any competition from other, lesser females setting up a nest nearby. Even the queen herself is not allowed to fool with the gene pool once it's been set. She mates only once in her life and stores all the sperm she'll ever need for the thousands of eggs she'll produce. (See pictures of the insect world.)

The rules, of course, don't prevent the other ants in the colony — which spend their lives tending eggs, gathering food and digging tunnels — from feeling a little randy now and then (never mind the fact that they're all, genetically speaking, brothers and sisters). But not only are those who give into the procreative urge pounced on, those who are even considering it are often restrained before they can try. The tip-off, as with so many other things in the animal world, appears to be smell.

Earlier studies had shown that a queen that senses potential competition from another fertile female will chemically mark the pretender; that female will then be attacked by lower-ranking females. Biologists Jürgen Liebig and Adrian Smith of Arizona State University suspected that something similar might go on even without the queen's intervention and believed the answer might lie in scent chemicals called cuticular hydrocarbons.

Ants that are capable of reproducing naturally emit hydrocarbon-based odors, and the eggs they produce smell the same way. Ants that can't reproduce emit no such odor. Liebig and Smith produced a synthetic hydrocarbon in the lab that had the same olfactory properties as the natural one, then plucked a few innocent ants from a nest and dabbed the chemical on them. When they were returned to the colony, they were promptly attacked — never mind that they had essentially been framed.

The sexual environment does sometimes loosen up in ant colonies. While the place may never become a Caligulan free-for-all, collective breeding will resume if the queen dies or is experimentally removed — but only until a new queen establishes herself and the reproductive lockdown resumes.

We complex critters might be glad to be part of a species that's free of such Draconian sexual rules, but Liebig doesn't think it's wise to get above ourselves. All manner of lawsuits, divorces and blood feuds can erupt over people breeding when — or with whom — they oughtn't. Often, the methods used to expose the cheaters aren't terribly different from those of the ants: more than one philanderer, after all, has been exposed by a whiff of the wrong perfume on his clothes when he came home. "The idea that social harmony is dependent on strict systems to prevent and punish cheating seems to apply to most successful societies," Liebig explained in a comment released with his paper. Regardless of the genome, in matters of sex, nature still appears to prefer us not to stray.

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