Adventures among Ants. Mark W. Moffett

any Pheidologeton. Raghavendra recommended I try the Western Ghats, a chain of low mountains famous for its forests and wildlife, just inland of the western coastline of India. On the road from Bangalore to the coast was a village named Sullia. I was told it had a forestry office where I would find both accommodations and advice.

      The next day, I learned a basic fact about Indian bus drivers: they were trained to accelerate around blind curves as if suicide were a career expectation. After a stomach-churning ride, I was dropped at the drowsy center of Sullia. I hoofed it to the forestry office, where I was delivered into the presence of Mr. Beeramoidin, who listened attentively to my explanation of ant diversity and then told me the guesthouse was full. Afterward, out under the roasting sun, my nerves jangling at the thought of the harrowing six-hour ride back to Bangalore, I kicked a tree in frustration—and got my first taste of Pheidologeton diversus. Hundreds of the tiny minor workers stormed from the earth, the major worker among them looking like an elephant among pygmies. Even Mr. Beeramoidin gave an impressed whistle, conceding with an enthusiastic rocking of his head that Sullia may be more of an ant haven than he thought.

      Struck by my preternatural ant-locating skills, Mr. Beeramoidin promised to find me a place to stay. An old man with a limp appeared. The two men conducted a rapid-fire conversation in the local Kanaka language, then the old man guided me down the road to a tiny room next to a mosque. Except for a thin sleeping mat, it was bare: no toilet, water, electricity. That night, I lay for hours watching geckos in the moonlight. Awakened at dawn by the call to prayer, I hobbled to my feet, rubbing my fingers across the areas where the mat’s reed latticework had impressed a design like a city map into my flesh.

      Finding ants in the dry forests around Sullia proved as arduous as it had been in Bangalore. That first morning, the ants in front of the forestry office had vanished, as had Mr. Beeramoidin, whom I never saw again. I decided to comb the forests, but they were desiccated. It wasn’t until the fourth day of looking that a diversionary hike at the edge of town through a watered plantation of stately oil palms brought me luck—a batch of Pheidologeton diversus crossing my path. I fell to my knees, thrilled to finally find some of Captain Bingham’s fabled swarming ants, and began inspecting the diversus column.

      Minor workers of the marauder ant riding on an especially large major (a “giant”).

      First, a marvelous sight: a major worker was careening along carrying a dozen minors, much like the elephant whose mahout, or trainer, had given me a wave from the back of his pachyderm soon after my arrival in Sullia. Except the ant passengers didn’t appear to be giving instructions to their beast of burden. Why were they there? I could see no evidence that the minors were cleaning or protecting their mount. I decided they were probably hitching a ride for a simple and practical reason: it takes less energy to ride than it does to walk. The smaller the individual, the more energy walking takes. Being bused by large ants saves the colony energy.²

      While I was in the entomologist’s “compromising position,” my nose practically brushing the frenzied ant workers that scurried beneath me, a young man of about my age walked up. Oblivious to my rapture over the ants, he started a conversation by saying his name was Rajaram Dengodi, which he explained meant “King God of All Mankind,” and inviting me for lunch. It turned out he was the son of the plantation owners and lived with his parents at the edge of the palm grove. When I arrived at their low whitewashed house, he proclaimed that I’d be sharing his room for the month.

      Despite the grandeur of his name, Raja was a low-key fellow with no apparent ambition other than to strum his guitar. But he proved an admirable companion and was eager to learn about ants. During that first week, I mapped the plantation and decided where to concentrate my search. Then Raja and I set about following the activities of the local Pheidologeton diversus. It quickly became evident that the colonies were huge. We saw several migrations with dense legions of ants moving their larvae and pupae to new nest sites, which suggested the workers numbered in the hundreds of thousands.

      We also witnessed the hunting and harvesting of meals on a massive scale. The workers carrying food moved along well-demarcated roads that remained active day after day. In time, I would learn that these tracks had as many functions as human road systems. Ant specialists call such persistent routes trunk trails. The marauder ant’s trunk trails are substantial structures, with a smooth surface an inch wide. Along them, the ants craft soil walls or even a complete roof of soil. The trails frequently lead belowground, especially where they cross dry or exposed stretches of earth.

      Hundreds of ants, and sometimes more, crossed back and forth on those trails every minute. In one extreme case I recorded eight thousand workers per minute climbing a cacao tree to flow into and out of a rotten pod over the course of a full day. Marauder ants excel at plundering large foods, such as fruit or carcasses, that take them a while to devour. But these expeditions represent only a small portion of their efforts. At any time, day or night, I could see them traveling from the trunk trails in ever-changing, reticulating networks, or, as Captain Bingham described them in Burma, in swarms. These extended into vegetation and leaf litter, where the ants’ activities were hard to document.

      I confirmed the observations of early naturalists that marauder ants can harvest seeds in bulk. More impressive, the ants returning to the nest labored by the dozen to cart centipedes, worms, and other creatures that, if viewed through ant eyes, would appear bigger than dinosaurs to us. A few dozen minor workers, each about 3 millimeters long, easily hefted the head of one of the doves the Dengodis had tried to induce me to eat after they found out Americans eat meat. Later, Raja and I saw a seething mass of workers rip up a live, 2-centimeter-long frog, pulling its twitching body taut to the ground and then flaying the meat. Raja and I studied the action with both horror and a newfound respect. That was the day I named them marauder ants.

      Marauder ants subduing a frog in southern India.

      Though Sullia was in no danger from the ant swarms, it was easy to believe Bingham’s report from Burma that droves of this species could overwhelm a village. Raja enthusiastically told me how the ants would sometimes pour into the family pantry and make off with supplies of rice and dried condiments.

      At dinner we reported to Raja’s parents about the marauders’ feats of predation, which I described as astonishing, particularly because the workers have no stinger, the weapon with which many predatory ants—especially those species in which the workers carry on alone or in small groups—disable victims. Mr. and Mrs. Dengodi, who took everything I said with great seriousness, no matter how eccentric the subject, listened as I explained that the marauders’ success with gargantuan prey seemed to rely on a coordinated group attack in which workers, individually inept, pile on high and deep, biting and pulling in such numbers that the victim doesn’t have a chance.

      I could attest personally to the effectiveness of that approach. While watching the frog, I’d made the mistake of standing in a throng of marauders. The sheer volume of the minor workers’ bites was enough to drive me away, with one major lacerating a fold of skin between my fingers.

      This scale of operations brought to my mind the most infamous raiders of all: the army ants.³ As a teenager in America’s heartland, far from any jungles, I had devoured popular descriptions of army ant swarms killing everything in their path. The stories often relied on florid writing, most famously in an unforgettable story by Carl Stephenson, first published in a 1938 issue of Esquire, “Leiningen versus the Ants”: “Then all at once he saw, starkly clear and huge, and, right before his eyes, furred with ants, towering and swaying in its death agony, the pampas stag. In six minutes—gnawed to the bones. God, he couldn’t die like that!” Although this is hyperbole, army ants do have an appetite for flesh and a coordinated battle plan that depends on sheer force of numbers.

      Like many army ants, marauders have no stingers. Rather than incapacitating prey with stings, they mob it. This gang-style predatory attack is just one element of both ants’ complex routine. How much deeper did the resemblance go? I knew that currently there are