We waited exactly one hour, then went to check the bait. There was an acute absence of ants and the cookies were undisturbed, except for the mound of crumbs on one card: Those had disappeared entirely and the paper was standing on end across the yard. “Maybe the squirrel ate it,” Josephine speculated. Then she confirmed, “Yes. It did.”
This, it seemed to me, was an illustration in miniature of how we humans deal with mystery: We take the limited set of characters and causes we already know (ants, squirrels, cookies) and spin stories around them, until storytelling slips into certainty.
We aren’t overwhelmed by ants in my part of the world, but I was surprised that we didn’t catch any. I began to spin my own theories. It had rained heavily the day before—the first real rain after a long drought—and I decided that perhaps the local colonies were too busy with flood repair to send out foragers. This is how we humans deal with mystery.
I would later learn that many ants deal with flooding fairly well. Lots of species can survive submerged for hours; some can even live underwater for days. Species that invest in expansive nests, like harvester ants, do spend time making flood repairs. But others can simply pick up and move when the waters rise.
Often it’s not water, but the lack of it that threatens ants. Their eggs and larvae quickly dry up if the humidity is too low. And yet ants thrive in deserts around the world by gathering dew and extracting moisture from food. Some species balance water droplets on their mandibles and carry them down into their tunnels (the surface tension of a small drop is great enough that it remains intact when suspended across the mouthparts). Diacamma rugosum ants in India build rudimentary mist-harvesting devices by placing feathers around the entrance of their nests.
TO BE AN ANT
Ants are bizarrely unlike people, and yet there’s a hint of human behavior at work in ant colonies. They are just strange enough, while also being similar enough, to prick the imagination. This has led thinkers throughout history to compare ants to people. Why aren’t we more like them? Or are we actually more akin to ants than we’d like to believe?
When King Solomon suggested that people should be more like ants, he was making a point about industriousness and self-motivation:
Go to the ant, thou sluggard; consider her ways, and be wise:
Which having no guide, overseer, or ruler,
Provideth her meat in the summer, and gathereth her food in the harvest. (my emphasis)
Ants are kind of amazing in this way if you think about it. They don’t have bosses or leaders, or a corporate structure or hierarchy. They don’t procrastinate. They don’t need deadlines. There is no top-down organization.
And the normal bottom-up drivers of individual behavior—the itch to reproduce and the instinct for self-preservation—don’t provide a tidy explanation for the motivations of ants either. The worker ants are all sterile females that can’t reproduce, and self-preservation obviously isn’t a priority, because they will sacrifice their lives to improve the fitness of the colony. A few workers of a Brazilian species, for instance, doom themselves to certain death each night by staying outside to seal up the entrance to the nest.
What makes an ant go? And what makes its actions contribute to the long-term strength of the colony, when it is neither controlled by a commander nor compelled by selfishness? It’s all very well for Solomon to call me a sluggard and tell me to be more like an industrious ant, but how do I accomplish this when I don’t even know how ants manage it? Corporate leaders and business theorists would love to figure this out. So would anarchists. Peter Kropotkin, the nineteenth-century anarchist philosopher, was fascinated by ants, and entranced by the possibility that humans might emulate them to achieve grand societal goals without leadership. In fact, the mysteries of ant behavior mirror two of the great questions of philosophy: How do we live together, and how do we attain a meaningful life?
Ant behavior starts to make a lot more sense if you think of the ants not as individuals, but as the cells of a body. It’s a metaphorical body—a body politic if you like. But there’s less friction in ant politics than in ours, because every ant in the colony has the same goal: Feed the queen and enable her to reproduce.
The queen is the ant that starts a colony. She lays the eggs that become all the other ants in the colony. Like an organism, the colony behaves as a unitary whole. It changes as it grows and has a clear life cycle. It has attributes of size, behavior, and complexity that are consistent throughout a species. The queen is its reproductive organ, and the workers are the digestive and circulatory systems.
Ants move resources around the colony by transferring food and water from mouth to mouth. Think of the colony’s tunnels as veins and the ants as blood cells running through them. Each ant has a second stomach, which serves as an internal backpack. If an ant needs food, she’ll tap a sister with an antenna, and the other ant will then provide her with a mouthful of pre-chewed snacks.
The queen sometimes lays eggs for food. They aren’t living eggs—they don’t grow into ants—but they are otherwise identical in composition. This egg cannibalism is simply a way to move nutrients around within the colony, just as a cell releases sugar into the bloodstream for use by hungrier cells. When the queen has plenty of nutrients and workers don’t have enough, she can share her surplus by laying these eggs.
A queen can also do the opposite. If she’s lacking in nutrients, she can suck the hemolymph—the ant “blood”—from developing larvae. She makes a small incision that heals quickly, and the young seem none the worse for it.
Thinking of a colony as a single organism can explain why workers do labor and sacrifice their lives without any possibility of individual reward. What these ants are striving for, from an evolutionary perspective, is to pass on their genes, but by proxy. They can’t give birth, so they rely on the queen, who shares 50 percent of their genes. The only way for a worker ant to increase her reproductive fitness is to improve the fitness of the colony. It’s wrong to suppose they are altruistic. Yes, they work tirelessly and martyr themselves without hesitation, but it’s out of the selfish motivation to perpetuate their colony’s genes.
The Wisdom of the Swarm
We have an inkling of what drives individual ants, but this opens a greater mystery: How do these individual actions add up to a colony acting with what looks like an informed strategy? Say I’m an ant going about my daily business, trying to help my colony succeed; what do I do? Should I go out and look for food? Cart larvae around? Dig new tunnels? Start moving the colony to a new location? Go to war? How can a part comprehend the needs of the whole?
Deborah Gordon has been watching harvester ants in Arizona for years, trying to figure this out. She and her students paint the ants with multicolored codes so they can track individuals to see what choices they make. Gordon has found that the ants pay attention to each other and switch tasks based on the chemical signals they pick up from their neighbors. If an ant is struggling to pull a big cricket back to the nest, the nearest ants may smell that struggle and go to help, perhaps releasing chemical “Workers Needed” signals of their own. “The pattern of interactions is the message,” Gordon wrote. From the interplay and spread of individual actions emerges something that looks like intelligence.
The idea of emergent intelligence is wonderfully spooky. But we shouldn’t glamorize it. This system is inefficient: Gordon found that large numbers of ants seem to do nothing all day. And if you’ve ever watched ants, you’ve seen them working at cross-purposes. That worker you recruited to help you pull that grasshopper may start pulling it in the opposite direction.
Of course, in human politics, people are always pulling in opposite directions. Could Kropotkin have been right? Instead of trying to agree on big societal strategies, which often fail anyway, would it work to simply pay close attention to our neighbors? It’s enticing to think that we might be able to give up election campaigns, political theorists, Federal Reserve members, city planners, military generals, and environ
mental regulators and instead sense (and fulfill) the needs of society through interactions with our neighbors. This, I suspect, would be an unmitigated disaster, but that doesn’t stop me from envying ants.
Imagine if you lived without conscious strategy or struggle in the assurance that your actions made a meaningful contribution to the commonwealth. What a gift it would be to simply know your place in the world, and to have no desire except to fill that role. Think of what it would be like to do away with all philosophizing and searching for meaning, all restlessness, all self-recrimination, all disappointment and anomie, and instead to simply do what you were meant to do.
And yet, I would object to being reincarnated as an ant. Though I’m constantly plagued by my second-guessing mind, I also find it’s incredibly useful. It (usually) keeps me from being duped. Whereas ants trust and cooperate, humans search for ulterior motives. Self-doubt is a burden, but the task of doubting others, the work of skepticism, investigation, and critical analysis brings me great satisfaction. My doubting, self-sabotaging mind is a pain in the neck, but it’s also, well, me.
Slavers and Parasites
The robotic quality of ant behavior—their ability to satisfy the needs of their colony without self-interest or apparent self-doubt—makes them perfect targets for con artists. Ants recognize their sisters by scent, but they don’t seem to distinguish between individuals. So, with just the right perfume, various species—beetles, mites, wasps, millipedes, flies, and others—are able to slip into the colony undetected. There is a rove beetle that uses a series of chemical signals to convince ants that it is a foundling infant somehow misplaced from the nursery. The ants carry the beetle home to the brood chamber, groom it, and feed it when it begs for food. This attentive care isn’t quite enough, however: The beetles also eat some of the ant larvae and eggs.
The rove beetle is just one of hundreds of species of ant parasites. As ant scientists E. O. Wilson and Burt Hölldobler put it in Journey to the Ants, “It is as though a human family were to invite gigantic lobsters, midget tortoises, and similar monsters to dinner, and never notice the difference.”
Ants can also be parasites themselves. Amazon ants, Polyergus breviceps, which live all around the Northern Hemisphere, hack into the simple information-sharing systems of other ant colonies to enslave them. To start a colony, an Amazon queen finds a nest of Formica ants and battles her way to the royal chamber. Howard Topoff, at the Arizona Museum of Natural History, had watched these heists and described them in an article for Scientific American.
In most cases the Polyergus queen quickly detects the entrance and erupts into a frenzy of ruthless activity. She bolts straight for the Formica queen, literally pushing aside any Formica workers that attempt to grab and bite her, . . . using her powerful mandibles for biting her attackers and a repellant pheromone from her Dufour’s gland in her abdomen. With the workers’ opposition liquidated, the Polyergus queen grabs the Formica queen and bites her head, thorax and abdomen for an unrelenting twenty-five minutes. Between bouts of biting she uses her extruded tongue to lick the wounded parts of the dying victim. Within seconds of the host queen’s death the nest undergoes a most remarkable transformation. The Formica workers behave as if sedated. They calmly approach the Polyergus queen and start grooming her—just as they did their own queen. The Polyergus queen, in turn, assembles the scattered Formica pupae into a neat pile and stands triumphally on top of it. At this point, the colony takeover is a done deal.
While the colony she has usurped feeds her, the Polyergus queen begins laying her own eggs. Eventually the Polyergus army rises up, supported by the Formica slaves. This army will, of course, eventually run out of slaves, because, without a queen, the stock of Formica workers will not be replenished. It is a crisis because Polyergus cannot survive without slaves. They cannot dig tunnels, or care for the young in the nursery. Amazon ants are slavers through and through, so dependent on this way of life that they no longer recognize food they pass on the ground: They only eat what slaves have chewed for them.
Weaponry and Diplomacy
Ants have an amazing armamentarium. Amazon ants make their raids using chemical propaganda signals, sending their victims dashing about aimlessly while they move in. A Malaysian Camponotus species can become a suicide bomber, blowing itself up and splattering all around it with green venom. Pachycondyla tridentata has a poisonous sting for big adversaries and the ability to produce sticky foam to bog down smaller attackers. Others are covered in spiked armor.
It’s not all violence among ants. There are species that can work together, like carpenter and acrobat ants. These two share a nest and cooperatively maintain gardens high up in trees. There are beggar ants that subsist entirely on the rubbish from another species’ nest. There are thief ants that live by stealing food from others. Even when ants have a direct confrontation, they generally try to avoid carnage. When two ants meet, they will touch antennae, reading the scent conveyed by the pattern of molecules on the other ant like a bar code. If it turns out that they are from different colonies, they try to avoid a fight through ritualized posturing: They open their mandibles as wide as possible, rear up on their back legs, and lift their abdomens threateningly. Often one ant will back down, averting violence.
Ant Language
Ants communicate primarily via scents. Every ant is coated in a layer of waxy hydrocarbons that volatilize, giving off the unique smell of the tribe. Ants also have a collection of glands spread throughout their bodies that contain ten to twenty chemicals. These are mixed in different proportions to convey different messages. E. O. Wilson and others dissecting ants under microscopes have been able to separate the chemical organs. Wilson found that when he wrote his name using the invisible fluid from one gland as ink, the ants followed the trail, making his signature visible with their bodies. When another of the chemicals was applied to an ant, her family became convinced that she was dead and deposited her in the trash heap; when she crawled away, they forcefully returned her to this cemetery.
Gordon says these experiments only give us the faintest understanding of chemical ant language. The meaning of each scent depends on its intensity, its combination with other chemicals, and the context: A smell that means one thing inside the nest might mean something very different in the middle of a battlefield. Exposing ants to chemical scents and trying to learn their meaning by watching the ants’ reactions, she writes, is like an alien trying to learn English by blaring the word “ant” at New York City and watching the human response.
What do these chemical messages smell like? Some chemicals don’t register in the scent receptors in our noses, or they exist in such tiny quantities that we can’t pick them up. But ant scientists tell me that all these chemicals together give some species a signature smell. Most ants carry the vinegary scent of formic acid, and some species smell strongly of citronella. If you crush just the heads of ants in the genus Odontomachus, they smell like chocolate. Weaver ants smell and taste like limes (it’s always worth tasting ants), and army ants smell like rotting meat or burnt hair. The chemical that gives odorous house ants their smell is nearly identical to the chemical that makes blue cheese stinky.
THE BACKYARD VELDT
Two weeks after our failed experiment as citizen-scientist ant collectors, we tried again. This time I was pickier about the locations. Instead of dropping the cards at random, I put them in spots where I’d seen ants before. There’s a piece of pressure-treated wood separating the grass from a row of ferns and camellias running along our fence, and as I peered down at this board I saw an ant walking purposefully forward. Another came toward it from the opposite direction. When they met they paused, tapped each other with their antennae, then continued on their way. I had found a trail. I set my index card squarely across this line of movement, put a quarter of a cookie atop it, and then sprinkled the crumbs stuck to my fingertips all around it.
Half an hour later, Josephine and I went back to check our bait. Not an ant in sight.
“Let’s just watch this one on the board for a while,” I told Josephine. I sat down cross-legged on the grass, and she sank into my lap. There were no ants to be seen, but as I scanned the ground, other movements began to pop out at me. A brown beetle about half the size of a three-year-old’s pinky-nail clipping dashed to the curving edge of a brown camellia leaf. It wiggled its long, pennantlike tail.
I pointed. “What do you think that is, Josephine?”
“An orckrises,” she said confidently.
For all I knew, she could have been right. There are some four hundred thousand beetle species, many more than there are of ants. (J. B. S. Haldane, one of the founders of evolutionary biology, joked that if there were a creator that shaped each creature, he must have had an inordinate fondness for beetles.) Perhaps Josephine had just named a new species. Perched on the leaf, it opened its shell, unfurled onionskin wings, and tumbled gracelessly into the grass.
Another beetle, a shiny round fellow, like a ladybug of one-tenth the normal size, trundled along nearby. A tiny, long-armed white spider was performing calisthenics on a dried leaf. A fly of some sort glided by noiselessly. A red spider mite dashed up a blade of grass and ran in circles on a leaf like an overcharged windup toy. A wolf spider of monstrous size compared to these itty bugs surprised us by taking a few steps out of a hiding place under the pressure-treated board. If I were being exhaustive, I could fill a book dedicated solely to the creatures we spied in a square foot of lawn.
Josephine called me back to the task at hand. An ant had ventured onto our index card. It lifted its head high, waving its antennae. Then it made a thorough investigation, touching the cookie from all sides and stopping to inspect the smaller crumbs. It did not pick anything up, and left the way it had come. I expected that this ant was going for reinforcements, but when other ants appeared, they came from another direction, following the trail I’d originally noticed. These ants bumped into crumbs and proceeded hastily around them. It was clear that these ants were not interested in pecan sandies. Perhaps they were some unusual sort of ant, I thought hopefully; perhaps I was about to identify a species that does not love sugar. I’d soon find out that I was wrong about the ants and the cookie’s enticing qualities: They are both sugary and fatty. But this only deepened the mystery: What was this ant that crawled over delicious food without any sign of interest?
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