“Hey, I’m dead!” — The Story of the Very Lively Ant

Here’s a question: How do ants know when another ant is dead? When Ed Wilson was a young assistant professor at Harvard in the 1950s, he wanted to know just that. He observed that when ants die — if they’re not crushed or torn apart — they just lie there, sometimes upside down, feet in the air, while their fellow ants walk right by without so much as a glance in their direction. That is, until about 2 days after the ant’s passing. That’s when the ant corpse appears to emit a chemical signal that changes the way the other ants behave dramatically. All of a sudden, what was once a pile of gunk on the colony floor becomes a “problem to be solved.” Once the signal is in the air, any ant that happens by the corpse grabs it and carries it through the colony to a refuse pile designated the graveyard and dumps it on a mound of equally-as-dead ants. Wilson decided to figure out what chemicals signal “I’m dead” to an ant. After much experimenting, he discovered a tiny drop of oleic acid mimicked the chemical emitted by dead ants. To research further, he placed a drop on the back of a live ant. As soon as he did that, a nearby ant came running over, slung the experimental ant on its back, hiked over to the graveyard and — even though the ant was very much alive — flung it onto the pile of really dead ants. Wilson confessed that it took the experimental ant a couple of hours to get clean enough to not be toted back to the graveyard. At least now Ed had the answer to his question about how ants know when another ant dies.