Benevolent ant suicide

Insects. I love insects. I love them in a less tolerant way than I once did — there was a time, not that long ago, when I didn’t kill  them when they came indoors. But still I love them.I guess these days  I love them in a more abstract sense. I love them the way one loves things one kills. You know, hunters, noble prey, blah blah blah.

I ran across this story in the news section of Science Magazine. It’s actually based on a study in American Naturalist about the Brazilian ants Forelius pusillus. As night falls, these ants seal up their ant hill against enemies. They do it so meticulously that a handful of ants have to stay outside to finish the job by kicking sand in the holes until the entrances disappear. Stuck outside for the night, most of the ants die. The scientists say it’s the first example of suicide for the good of the colony absent an immediate threat. Some speculate that these self-sacrificing insects were older ants who, I guess, knew their time on earth was short. I don’t buy it.I mean, ants have, what, six, neurons tops, right? (OK, a couple hundred thousand. Whatever! ) They’re not thinking they don’t want to be a burden to their children. Still, what genetic program would get any ant to decide to stay outdoors to die? What series of events would cause such a practice? Obviously, self-sacrificing ants don’t have higher reproductive success.

So, here’s my theory: It’s an accident. Spend any time at all watching ants wander around and the randomness of their behavior is almost frustrating — or frustrating if you’re the kind of person who starts identifying with the ants. They walk back and forth accomplishing nothing.While some seem to be going someplace, there are always a couple pacing out figure eights. So, I think a couple of them just wander outside at sunset because they missed the signal that said, go home and go to bed.

Of course, that doesn’t explain why they turn around and fill up the entrance instead of digging their way back inside. But it’s the best I can manage for the moment.

I just realized that I said a handful of ants stayed outside. Considering the size of the ants, that would be, what, most of the colony? Actually, only seven or eight commit suicide.

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