The Zombie Ants: When ants are accidentally marked as dead, they find a way to rejoin the living

Edward O. Wilson in The New York Times:

Every corpse is an ecosystem. Each fallen bird, landed fish, beached whale, decomposing log, plucked flower is destined to change from a conglomerate of giant molecules, the most complex system in the universe known, into clouds and drifts of much smaller organic molecules. The process of decay is driven by scavengers, in nature beginning with vultures and blowflies and ending with fungi and bacteria. What do ants do with their dead? In many species, if a colony member is badly injured in the field it is carried home and eaten. If injured only moderately, it may be allowed to live and heal. Most ant warriors that die in battle outside the nest never return. They instead fill the jaws and beaks of predators. An ant that dies from old age or disease inside the nest simply comes to a standstill or else falls to the side with her legs crumpled up. In most cases, she is allowed to stay in place. After, at most, a few days, a nest mate picks her up and carries her out of the nest or to a refuse pile in one of the chambers within the nest. In this cemetery chamber is also dumped miscellaneous refuse, including the inedible remains of prey. There is no ceremony. It occurred to me early in my studies of chemical communication in ants that the bodies of the dead are likely recognized by the odor of their decomposition. Of all the substances uniquely present in dead insects, one or more must be the signal that triggers corpse disposal by ants. If live ants demonstrably use such molecules to release other instinctive social behavior in the service of the colony, why not in death also?

…As a first step, I made extracts of decomposing ants. I put droplets of this material on “dummies” of dead ants made of flecks of balsam about the size of workers. When these were dropped into nests of laboratory colonies of harvesting ants, each was picked up and taken speedily to the refuse pile.

…So I asked a new question: What would happen if I daubed a live, healthy worker with one of the funereal substances? The result was gratifying. Worker ants that met their daubed nest mates picked them up, carried them alive and kicking to the cemetery, dropped them there, and left. The behavior of the undertaker was relatively calm, even casual. The dead belong with the dead. The daubed ants did what you and I would do if we were turned into zombies: We would take a bath.

More here.