An Ant With a Tool Chest Built into Her Face

Oh the errors that survive in a book even after you look at its text times beyond counting! The day after the book was finalized, May Berenbaum, an entomologist with a knack for writing vividly about her subjects, reminded me that the springtails that I describe in Adventures Among Ants as “the rabbits of the insect world” are no longer considered insects by most experts (though others disagree.).

My observations on springtails as the prey of the trapjaw ant Acanthognathus teledectus were first reported in the March 1989 issue of National Geographic Magazine, one of many instances in which my National Geographic articles reported on new findings.  This trapjaw ant has tiny colonies nesting inside hollowed-out twigs on the forest floor. As is the case in most small societies, human or ant, single individuals are generalists, capable of carrying out work on their own.  In fact, I call this trapjaw species the “Swiss army ant,” because each worker has a tool chest built into her face for catching and eating prey and other tasks. 

Catching a springtail takes some doing.  First the slow-motion stalk.  Then contact with special trigger hairs extending from the mandibles that cause the mandibles to spring forward like a bear trap.

Then the ant reaches around with the stinger at the tail end of her abdomen and injects a toxin that knocks the springtail out.

I noticed that the ant usually carries the springtail home held absurdly high as possible in the air.  This turns out to be for good reason: on occasion, a springtail will revive from its toxic injection and starts kicking with the long “spring tail,” or furcula, which until then was held tight under its body.  If the springtail isn’t grasped strongly, these kicks can free it while throwing the ant high into the air.

Back in the nest, the ants use a smaller set of jaws—actually teeth extending from the long “bear trap jaws”—as practical tools to chew their food.  Because both sets of “jaws” are really part of the same, welded whole, chomping with the small jaws sets the long pair flailing back and forth, which can knock around the neighboring ants in the nest.  This is an example of the improvisational and often sloppy designs that can emerge from evolution by natural selection, as Stephen Jay Gould famously discussed in his essay on the panda’s thumb.

This essay expands upon the discussion on pages 42-44 of AAA.