Adventures among Ants. Mark W. Moffett
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ant scout might face would seem to be no different from those encountered by any kind of ant that searches on her own, entering a hostile world without backup. Wouldn’t the rewards, for the group, far outweigh the risk to the individual?
Perhaps risk has little to do with it. Watching the marauder ants cart off fruit, seeds, and animal prey, I suspected that the unpredictable quality of their plunder simply made such reconnaissance pointless. Or maybe any tendency for an individual ant to scope out her surroundings—and in so doing wander off on her own—somehow interferes with the mass-foraging process, in which a total fixation on tracking the pheromones of the group is key.
Humans are accustomed to supervision and chains of command that encompass every level from presidents to petty administrators. Roman soldiers wheeled and charged under the direction of officers moving through the ranks. For certain ants, too, transient leadership roles do exist, in some circumstances—as with the successful Leptogenys scout I observed in India, who always stayed with the assembled troops, guiding them to the termites she found. What, then, of the leadership role of individuals in a marauder ant raid?
Once, at the Botanic Gardens, I attempted the near impossible: to follow an individual marauder minor worker entering a swarm raid. I picked her out because she was missing the end of one antenna. It was too difficult to focus binoculars on her, so I tied fabric from an old T-shirt across my face to keep my breath from disturbing the ants and got in close. I followed “Stumpy” for a minute through the tributaries of workers in the raid fan. She dashed wildly for a moment near the commotion of ants on a beetle larva—agitated, I surmised, by alarm pheromones released from the poison glands of the struggling workers—then kept going. Approaching the raid front, she wandered and finally entered a stream of ants, where I lost her.
Nowhere along her route did I observe other individuals guiding her, or her influencing other workers. As with army ants, the marauder ant is a species with no established leaders. If I could communicate “take me to your leader” to one of them, it’s unlikely I would be shown the queen, who, like all ant queens, lays eggs but coordinates nothing. Nor does any of her workers inspire, cajole, or force the whole army to take a line of action. Proverbs 6:6–8 makes this point: we must “go to the ant” and “consider her ways, and be wise” because she does the job without “guide, overseer, or ruler.” King Solomon must have been a devoted ant observer to reach this conclusion. In all likelihood, he grew up watching Messor barbarus, the dominant seed harvester of the Mediterranean, which indeed “gathers her food for the harvest,” as the Bible tells us.
The hardworking ant described by King Solomon was likely a solitary-foraging seed harvester ant such as this Messor barbarus from the Kerman region of Iran.
A century ago, Harvard’s erudite ant scholar William Morton Wheeler called army ants “the Huns and Tartars of the insect world.”29 But no myrmecologist has ever identified a Genghis Khan or Attila among them. At best, an individual in the raid may be momentarily better informed than others, giving her a brief and local influence.30 That could happen when a worker at the front sends out recruitment signals to prey—but even then she is likely to be acting in concert with nearby sisters. No ant, in fact, can conceive of the raid in its entirety, know where it is going, or anticipate how the masses will respond when food is found or enemies encountered. A raid arises through a series of simple actions by each worker and others like her, in an engagement that can truly be described as “self-organized.”
Humans constantly have to work around issues of self-interest that would otherwise impede the emergence of social institutions and infrastructure. Our clannish devotion to networks of kin and friends has proved particularly problematic in the context of modern warfare. The solution has been to divide armies into squadrons small enough for the troops to bond and be willing to take risks for one another.31 Ant workers, of course, don’t recognize nestmates as personas in the way I picked out the stump-antennaed individual,32 and they never throw themselves in harm’s way so that particular compatriots might live. What we perceive in ants as acts of heroism and devotion are really more akin to acts of patriotism. Since it is only the superorganism that matters, ant workers instinctively toil and die for the benefit of the colony, without recognition or recompense other than the remote possibility of augmented reproduction by the queen, the one member of the group who is indispensable. Mortality seems to be the basis of the domestic economy for prodigious, combat-savvy ant societies.33 It is difficult not to think of the Spartan mothers who sent their sons off to battle saying, “Come home either with your shield or on it.”34 Brute force, apparently, is the key to tactical success for mass-foraging marauder and army ants.
3 division of labor
In the short grass of the Singapore Botanic Gardens, I dropped to my knees, then lowered myself to my elbows and, at last, to my stomach, eye pressed to soil, camera extended in front of me. My perspective standing up had been abstract, like that of a general assessing the movements of troops from a hilltop, where they were more pawns in a game than people engaged in a life-and-death struggle. Now, seen close-up through my camera lens, a marauder minor worker stood tall and solid before me, antennae moving as if to sniff me out. Her forebody was raised, forelimbs almost lifted from the ground, mandibles open. She was ready to pounce. Suddenly I saw the silvery blur of some creature, through my lens the size and shape of a tank, and the worker was yanked from her spot. I recognized the beast as a roly-poly, or pill bug, a quarter-inch multilegged crustacean presumably flushed at the raid’s front lines.
My worker had seized one of the pill bug’s furiously moving legs. Though knocked about violently, she managed to hold on. Two other minors, and then three more, grabbed the pill bug by other legs or the edge of its carapace. One whose head somehow got smashed released her grip and fell away. The others were strong enough to bring the pill bug to a halt. It tried to roll into a ball—a ploy that gives the bug its common name—but the tightly anchored workers prevented it from protecting itself. From the left, a media worker lumbered into view. She used her antennae to survey the scrimmage. Then she opened her club-shaped mandibles wide and struck. The pill bug’s pale underbody went limp. Watching this skirmish conclude, I couldn’t help but think about how groups of early humans brought down woolly mammoths using nothing but guts and some simple stone tools.
When I left Boston for Asia in 1981, I had a premonition that I would discover amazing things about the marauder ant—so amazing that my thesis committee might suspect I had concocted stories while smoking an illegal substance with an Indian guru. Knowing I had to come home with indisputable documentation, before I left for Asia I bought a how-to book on photographing supermodels, Cosmopolitan-style. With $230 in equipment that included a used Canon SLR, a macro lens, and three $15 flash attachments that gave me electric shocks, I miniaturized the glamor studio the book described by affixing the flashes to the front of the lens with a pipe clamp. By adjusting the strength of my lights, I adopted the concepts of “fill” and “hair light” to accentuate the gleaming exoskeletons of my minuscule models, defining each limb and chiseling every fiber on film.
During my travels in Asia, I used my camera to observe ants, triggering it whenever something happened that I wanted to examine later. In India, trying my equipment for the first time outside, I was stunned to see that through my lens, ants towered. Soon I was stalking them through the viewfinder with all the thrill nineteenth-century hunters must have felt tracking lions. With both quarries, the trick is to go unnoticed, to catch everyday behavior without being bitten—admittedly a more high-stakes proposition with a lion. Still, when tracking an ant in this way, I would forget her size, and she gained all the grandeur of the king of the jungle.
A minor worker stands a couple of millimeters tall. Photographing such a tiny insect requires concentrated effort and lots of illumination. When I focused the camera on my leg, my cheap flashes gave such an intense pulse of heat and light that smoke rose from my jeans. Fortunately, reducing the setting to one-quarter power solved the problem while providing sufficient exposure, but even then, the part of the picture in focus was often only a fraction of a millimeter deep—the length of a paramecium. With