|Publisher:||University of California Press|
|Edition description:||First Edition|
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Adventures Among Ants
a global safari with a cast of trillions
By Mark W. Moffett
UNIVERSITY OF CALIFORNIA PRESSCopyright © 2010 Mark W. Moffett
All rights reserved.
strength in numbers
We tracked marauder ant trails on steep forested slopes, accompanied by the "wish-wash" sounds of hornbills in flight and mournful calls from a green imperial pigeon. As nightfall approached, we made our way back to the village of Toro, in a valley of brilliant green paddy fields at the edge of the forest. My guide, Pak Alisi, invited me into his home for tea. "You know," he said, "here we call the ant you study 'onti koko.' That means you always find many together."
Yes, I agreed. With the marauder ant, the group is everything.
FIELD NOTES, SULAWESI, INDONESIA, 1984
"We have three kinds of ants here," declared Mr. Beeramoidin, the forestry officer at the village of Sullia in India. "A black one, a big red one, and a small red one that bites."
I was twenty-four, a graduate student on a quest for the ant I had reason to believe had one of 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." 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.
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.
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.
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. 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 as many species of ant as there are of bird—perhaps 10,000 to 12,000—and that the marauder and the army ant are no more closely related than the hawk and the dove.
Convergence is the process by which living things independently evolve to become alike, as a result of like responses to similar conditions or challenges. The wings of bats, birds, and bugs are convergent because they are limbs that have been independently modified to function in flight; the jaws of humans and the mandibles of insects are convergent because both can be used to hold objects and chew food. If the marauder ant and army ants proved to be alike in how they hunt and capture prey, it would be a similarly marvelous example of evolutionary convergence. That day in Sullia as I watched the ants dispatch that unfortunate frog, I made a decision that would affect the first years of my budding professional life: I would study the kill strategy of the marauder ant. I would make that my quest.
FEEDING THE SUPERORGANISM
Standing in a Sullia field on a tepid afternoon, with Raja's guitar providing an incongruous musical accompaniment to the massacre at my feet, I felt like a general observing his troops from a hilltop and trying to make sense of the skirmishes below. My brain was whirling: one moment, trying to picture what it's like inside one of those tiny, chitinous heads; the next, envisioning all the ants at once, forming a kind of arm flung over the ground with fingers that were rummaging through the soil and low plants.
The nineteenth-century philosopher Herbert Spencer was the first to treat in detail the simultaneous existence of these two levels, individual and society, and in 1911 the ant expert William Morton Wheeler came up with the term superorganism to describe ant societies specifically. Both men saw an ant colony not merely as an individual entity, as one might think of a bank or a school, but more specifically as the exact equivalent of an organism. They could readily make this point because others had already described the human body as a society of cells. The superorganism concept took on real meaning for me as I watched marauder ants. Before coming to India I had read an essay by the physician and ant enthusiast Lewis Thomas, who took Wheeler's writings to heart:
A solitary ant, afield, cannot be considered to have much of anything on his mind; indeed, with only a few neurons strung together by fibers, he can't be imagined to have a mind at all, much less a thought. He is more like a ganglion on legs. Four ants together, or ten, encircling a dead moth on a path, begin to look more like an idea. They fumble and shove, gradually moving the food toward the Hill, but as though by blind chance. It is only when you watch the dense mass of thousands of ants, crowded together around the Hill, blackening the ground, that you begin to see the whole beast, and now you observe it thinking, planning, calculating.
Like a more traditional organism, a superorganism is most successful when its activities are carried out with maximum productivity at the group level. Consider the cells of a human body, an assembly of trillions. Although these cells may be doing rather little as individuals, collectively they can yield results as intricate and choreographed as a dancer's in a corps de ballet. I developed a feeling for a marauder colony as an organism. I watched as the ants worked together like the organs in a body to keep the ensemble healthy and stable, with their trails serving as a nervous system used by the whole to gather knowledge and calculate its choices. With mindless brilliance, this colony-being established itself, procured meals and grew fat on the excess, engineered its environment to suit its needs, and fought—and on occasion reproduced—with its neighbors. I imagined that, given enough time, I could watch each superorganism mature, spin off successors that bred true through the generations, and die.
How do the members of an ant superorganism supply food for the whole? Unlike the body of an ordinary organism, a colony can send off pieces of itself—the workers—to find a meal. Regardless of species, once an ant detects food, her searching behavior stops and is replaced by a series of very different harvesting activities: tracking, killing, dissecting, carrying, and defending. In the majority of species, an ant can mobilize others to assist her. This communication practice is known as recruitment and usually involves chemical signals called pheromones. Often, a wayfaring ant releases a scent from one of a battery of glands on her body, a mixture that serves to stimulate or guide her nestmates. The mobbing of marauders at prey reflects the speed and effectiveness of their recruitment.
Excerpted from Adventures Among Ants by Mark W. Moffett. Copyright © 2010 Mark W. Moffett. Excerpted by permission of UNIVERSITY OF CALIFORNIA PRESS.
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Table of ContentsÍcaro|Ícaro|Ícaro|Introduction: Travels with My Ants A Brief Primer on Ants Marauder Ant, the Ultimate Omnivore 1. Strength in Numbers 2. The Perfect Swarm 3. Division of Labor 4. Ícaro|Ícaro|Ícaro|Infrastructure 5. Group Transport African Army Ant, Raiders on the Swarm 6. Big Game Hunters 7. Clash of the Titans 8. Notes from Underground Weaver Ant, Empress of the Air 9. Canopy Empires 10. Fortified Forests 11. Negotiating the Physical World Amazon Ant, the Slavemaker 12. Slaves of Sagehen Creek 13. Abduction in the Afternoon Leafcutter Ant, the Constant Gardener 14. A Fungus Farmer’s Life 15. The Origins of Agriculture Argentine Ant, the Global Ícaro|Ícaro|Ícaro|Invader 16. Armies of the Earth 17. The Immortal Society Conclusion: Four Ways of Looking at an Ant Acknowledgments and a Note on Content Notes Ícaro|Ícaro|Ícaro|Index
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"Packed with graphic enthusiasm...[and] provocative thoughts. . . . [Moffett] writes with an entertainer's instinct for hooking a restless audience."New York Times
"[Adventures among Ants] is hefty, yet aerodynamic. It's really good for killing ants."The Colbert Report
"Take a look at daring eco-adventurer Mark Moffett's spectacular new ant book." - Margaret AtwoodNew York Review of Books
"Superb book by a first-class writer with an unsurpassed feel for ants."Library Journal
"Adventures Among Ants may reach a broader audience than other recent publications and therefore stimulate interest in ants among a new generation."Bioscience