the most complexly organized societies in existence. A column of dust-speckled sunlight emblazoned a rectangle on the floor too bright to look at directly—a reminder of the intense dry heat outside. It was late November, and I was worried my choice of season wasn’t giving me the best weather for ant hunting.
As Mr. Beeramoidin spoke, his round, bespectacled head rocked from side to side. I had learned that this meant his attention was friendly and focused on me, and though I had only been in India a month, I had already adopted the same habit. I also found myself chewing betel nut, wearing a Gandhi-style lungi around my waist and flip-flops known locally as chapels on my feet, and using words like lakh, meaning a hundred thousand, to describe the number of workers in an ant colony.
Rocking my head in turn, I told Mr. Beeramoidin it was likely that scores of distinctive ants lived within a stone’s throw of his office, though even an experienced person would need a strong magnifier to tell many of them apart. I sought just one of them, Pheidologeton diversus, a species to which I later gave the name “marauder ant.”
In 1903, Charles Thomas Bingham, an Irish military officer stationed in Burma, provided detailed and theatrical descriptions of this ant. In one memorable passage, he wrote that “one large nest . . . was formed under my house in Moulmein. From this our rooms were periodically invaded by swarms, and every scrap of food they could find, and every living or dead insect of other kinds, was cleared out.” The locals found the swarms overpowering. “When these ants take up their abode in any numbers near a village in the jungles, they become a terrible nuisance. . . . I knew of a Karen village that had absolutely to shift because of the ants. No one could enter any of the houses day or night, or even pass through the village, without being attacked by them.”1 In spite of the vividness of Captain Bingham’s report, the group remained a biological mystery.
I had arrived in India in the fall of 1981, primed to explore the social lives of the minor, media, and major workers of Pheidologeton diversus. My first stop had been Bangalore, more specifically its prestigious university, the Indian Institute of Science. My host was Raghavendra Gadagkar, a professor whose subject was the social behavior of wasps. He believed in learning from experience and smiled at my naïveté and youthful enthusiasm. Rather than teaching me how to eat rice without utensils, in the local fashion, for instance (the nuances of handling hot food bare-handed are many), he dropped me at the door of a local restaurant, recommended I order the “plate meal,” and came back for me an hour later. During that first lunch I spilled more than I ate.
Bangalore was going through a dry spell, and I had trouble finding 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
