The Wasp That Brainwashed the Caterpillar

by Matt Simon

  AND NOW, FOR MY NEXT PARTY TRICK . . .

  Lacking the sociable weaver’s safety of a community, a bird known as the fulmar has evolved a rather more inventive way to defend itself: Its chicks will vomit a fetid oil on predatory birds up to ten feet away. But this is more than a wretched inconvenience. That oil won’t come off, and this is a big problem for a bird that needs its feathers to remain clean in order to stay waterproof. The fulmar’s victims can actually perish after a good coating of puke.

  But leave it to humans to make the best of a bad situation. In the 1800s, the people of the Scottish islands of St. Kilda sold fulmar feathers as stuffing for mattresses and pillows, after fumigating them, of course. The feathers were said to keep lice and bedbugs away, yet, sure enough, after three years the smell would return, to the horror of the sleeper. At that point you pretty much had to burn your house to the ground.

  It sounds like pure anarchy, I know, and I promised you an anarcho-syndicalist commune. But there actually seems to be a cryptic signal of order right below the sociable weaver’s beak: a bib. Extending down their necks are bands of black that contrast with their otherwise cream-colored feathers. It’s what’s known as a badge of status. The longer the bib is, the higher the bird is ranked and the more dominant the bird is toward its peers, though individuals at the top don’t find themselves challenged much at all. It’s so effective that overall size, a popular marker of dominance in the animal kingdom, isn’t as important to the bird’s status as is the size of its bib.

  Thus it seems that order in social weaver society comes by both the bib and the chase. And by sticking together and overriding that pesky evolutionary proclivity for selfishness, sociable weavers have a distinct advantage out there on the plains of southern Africa. Offering a clue to how this sociability evolved in the first place are the nests themselves. Because the chambers are not interconnected, this suggests that sociable weavers, like American settlers circling the wagons, once built smaller nests near each other, perhaps to enjoy the safety that comes with numbers (sending out alarms, forming gangs to chase away predators, etc.). Over time they merged the individual nests into some of the most magnificent homes on Earth and, with selfishness largely overruled, the sociable weaver came to rule the savanna. All it took was a good old public beating now and then.

  Hero Ant

  PROBLEM: Rain forests are wet and packed with disagreeable organisms.

  SOLUTION: The so-called hero ant creates what is surely the simplest, yet most perplexing ant nest on Earth. And defends it—kamikaze-style.

  Oh, how the pursuits of natural history have changed over the centuries. Back in the day, Maria Sibylla Merian and Charles Darwin and Alfred Russel Wallace were prone to wandering, sometimes for years. After all, chances were the maps that could help them didn’t yet exist. And perhaps that was all part of the romanticism of early natural history: There was as much an aim to unveil new species as there was a wanderlust that sometimes involved falling victim to a caterpillar. But as science matured and grew increasingly complex, natural history’s adherents had to fragment into specialties: Entomologists love their bugs, ornithologists their birds, ichthyologists their fish. The wandering generalist grew endangered, and not only because a good amount of them died in the process. These days, cash-strapped scientists are on expensive, and therefore necessarily precise, missions.

  And so in 2013, Brian Fisher, one of the world’s foremost experts in ants, found himself in the remote rain forests of Madagascar, carrying the ultimate luxury of the modern field biologist: the iPad. He didn’t have the resources that Darwin had (thanks to dear old rich Dr. Papa Darwin, who bankrolled his son’s adventures—perhaps reluctantly, but that’s a whole different story) or the luxury of time that Merian and Wallace had. What he did have, however, were thirty porters to deal with, porters who hadn’t the slightest idea where they were headed. Hence the iPad, loaded with the latest imagery from an imaging company that had agreed to train its satellite on a mountaintop near where Fisher had, on an earlier expedition, collected the mysterious ear ant—soon to be given the honorific of hero ant—whose nests jutted out of the sides of cliffs as earlike funnels. He and his colleagues and the porters were there to figure out why exactly an ant nest would appear to have a megaphone facing out to the world.

  NEED TO PASS THE TIME SO YOU DON’T DIE WHILE SCUBA DIVING? THERE’S AN APP FOR THAT (ALSO A CLICHÉ, BUT REMEMBER OUR RULE)

  I once interviewed a pair of marine biologists who regularly scuba dive four hundred feet deep, a ridiculous figure if survival is among your interests. That’s so deep that of the seven total hours of diving time, they can spend only twenty minutes down at their destination because they have to factor in the time spent ascending and decompressing to avoid the bends. They make a whole bunch of calculated stops coming up, which begin at a minute long, culminating in ones near the top that last two hours. So how do they stave off insanity? By playing Angry Birds on a waterproofed iPad, which I imagine they could even write off on their taxes. Well played, scientists.

  The team was working off three theories that could explain the perplexing domicile. For one, the funnel might serve as an obstacle for any number of small marauding predators in the rain forest—the hero ants may post up at the edge of the structure and fight the invaders from an elevated position. Two, it could be an antiflooding measure. This is, after all, called a rain forest on account of being a forest where it rains a lot. Third, the funnel could help facilitate air flow, for a shape like that would presumably work much better than a simple hole for ferrying oxygen in.

  Now, I take it you’re imagining quite the network of tunnels connected to that megaphone entrance. But this isn’t that kind of ant. The funnel itself is less than two inches wide, and it opens into a single chamber that’s only three inches deep. That’s all. Here you’ll find the queen and her young and all the workers shuffling in and out. It’s the only known ant on Earth that does this, but such puzzling architecture is likely a product of the material in which the ant makes its home.

  It turns out that the wet clay of the walls isn’t conducive to gas exchange between the atmosphere and the nest’s interior, so there’s a real danger of carbon dioxide accumulation inside. The nest is probably so shallow because it has to be: It’d be hard to get circulation going in meandering tunnels. And what Fisher and his team calculated was that by building out that funnel, the ants boost the air flow into the nest by six times, no small matter when their home only has one air duct. The team also found that the funnel helps keep out water. A simple tube jutting out from the nest, though, would have had the same benefit. Perhaps it was that the funnel-building behavior evolved to facilitate air flow, and had the bonus of keeping the nest good and dry.

  So what about the tunnel aiding in defense? Well, that’s where a field biologist’s job gets fun. The team placed eight other ant species next to hero ant nests, including individuals from other hero colonies and two species with an appetite for the larvae of other ants, and observed how the invaders navigated the funnel and how the unwitting hosts reacted. It turned out the funnel mattered . . . not one iota. The hero ants didn’t sit there at the entrance and defend, and every single one of the other ant species had no problem scrambling into the nest. And even then, they didn’t immediately set off any alarms. The heroes got worked up only when they directly ran into the invaders.

  And, boy, did the heroes get worked up. They didn’t swarm, like army ants so famously do. Instead, hero ants turned out to be one-on-one scrappers. Fisher and his colleagues watched plucky individual hero ants not just snag an intruder, but drag it out to the edge of the funnel and then—leap. Locked in combat, the pair would tumble off the cliff, and thus did the lowly “ear” ant become the “hero” ant. Both parties could survive the impact, since they’re so light and have such strong exoskeletons. Inevitably, the hero would make its way back up to the nest, on account of these being its stomping grou
nds, but the odds of the intruder doing the same to try its luck a second time were slim. And the ant’s return is a welcome one: It’s truly a precious resource for the colony’s queen, who’s ruling a society of as few as a dozen individuals.

  FURTHER ADVENTURES IN WATCHING ANTS FALL OFF THINGS

  If we might call the hero ant’s defense a kind of intentional chaos, the ant species of the Cephalotes genus are surely the elegant skydivers of the ant world. These are tree dwellers, and when threatened they will leap off a branch, legs splayed. With a few deft movements of their limbs, they can steer themselves right back to the trunk of the tree and make their way up to the colony again. We know this because a scientist once took the time to sit in a tree and watch them—but not before picking them up and painting them white and tossing them off himself. I mean, it’s okay, really, because 95 percent of the ants ended up landing back on the trunk. As for that other 5 percent? Well, no one ever said skydiving doesn’t come with risks.

  Now, the classical high-school-biology notion of ant sex is that winged males, whose only purpose is to reproduce, and queens from a given neighborhood’s colonies take flight and mate. Afterward the males die and the females land somewhere, break off their wings, and start a new colony from scratch.

  But not with the hero ant. The hero ant queen, known rather unflatteringly as an ergatoid, has no wings and appears to wait for the winged male to come to her. It isn’t yet entirely clear whether it happens when she’s in her original colony or when she’s moved to a new one, but it doesn’t much matter for her. The important bit is that the queen always takes a squad of workers, which are all female, with her when she packs up and leaves, meaning she’s got a workforce to build a new home wherever she sees fit. In winged species of ant, the queen has to wait to have her young before the workforce really spins up. So, however precarious the situation of the hero ant colony may seem, the society always has a pretty good start at things. It’s just that a tumble or two comes as part of the territory.

  CHAPTER 4

  You Live in a Crummy Neighborhood

  In Which Tiny Gummy Bears Go to Space and Zombie Ants Stagger Through the Rain Forest

  Sometimes even the finest home in the finest mouth or anus simply won’t do: Some neighborhoods are just terrible. So animals have a couple options. They can move away, or they can adapt. A spider sick of getting eaten, for instance, could move into the water. Or if you’re the tunnel-dwelling naked mole rat, you could evolve stretchy skin that helps you squeeze through the passages, skin that may hold the key to curing cancer.

  Water Bear

  PROBLEM: Mud is a lovely place to live—as long as it stays mud.

  SOLUTION: Should its muddy home start to dry up, a tiny critter known as the water bear can dry out almost completely for up to thirty years, only to reanimate once it hits water again.

  Life doesn’t like being told no. Even in the deepest depths of our oceans, where frigid temperatures and crushing pressure and scarce food combine to make for an unpleasant habitat, life endures. Everywhere you’d figure to be devoid of life has something holding on: Wildlife proliferates in the contaminated forests of Chernobyl while bacteria kick back in the scalding hot springs of Yellowstone. Only in the vacuum of space should we expect sterility, for surely nothing could survive there.

  Well, as it turns out, there’s one tiny critter that especially doesn’t like being told no.

  In 2007, the European Space Agency launched a satellite with very special passengers indeed: two species of tardigrade. Also known as water bears—on account of resembling bears, or, even more so, gummy bears, only with twice as many legs and not nearly the same taste—these microscopic invertebrates had already grown legendary for their resistance to heat and cold and radiation. So some scientists got an idea: Why not fire them into space? And so the scientists did. Once these water bears reached low Earth orbit, they were exposed to the vacuum for ten days, then brought back home. Incredibly, they survived. Like, really well. Not one or two that came back coughing and moaning, but a whole slew of them. Their eggs even survived and hatched into healthy young.

  Here’s the problem, though. The water bears cheated. Don’t get me wrong, surviving space is a feat that boggles the mind. But they have an evolutionary ploy. You see, while these creatures live in dirt and moss and such, they need those materials to be at least a little bit moist. But should their habitat start drying out, water bears can dehydrate down to 3 percent of their typical water content, folding in on themselves and entering what’s known as cryptobiosis, essentially suspended animation. (Cryptobiosis was first discovered in a different creature way back in 1702 by a scientist named Antony van Leeuwenhoek, who collected dried sediment from house gutters and added water. The material erupted with life—“animalcules,” as they were known then, a blanket term for itty-bitty creatures.)

  THE ADVENTURES OF MUTTNIK: THE MOST RUSSIAN TALE IN THE HISTORY OF RUSSIA

  There’s a long, exceedingly weird history of sending animals into space, and leave it to the Russians to provide most of the weirdness. The first animal to enter orbit was a stray dog recruited from the streets of Moscow (the thinking went that strays were scrappier and better cut out for surviving space) only nine days before her rocket launched in 1957. But there was a glaring hitch: No one had had time to think up a plan for reentry. It would therefore be a one-way trip for the pooch. So before launch, a Soviet scientist took her home to play with his kids. “I wanted to do something nice for her,” he recounted. “She had so little time left to live.”

  The pooch never made it to reentry—she overheated and perished a few hours after launch. But she’s now immortalized in a Moscow monument, standing confidently on a rocket. The Russians called her Laika, but in America, she’ll forever be known as “Muttnik.”

  It’s in cryptobiosis that water bears are virtually indestructible, as their bodies mobilize a sugar that replaces the lost water and protects their cells. They can stay like this for at least thirty years and still reanimate fine. So, that said, when the scientists sent their water bears into space, they were dried out, only to be reanimated back in the lab, a process that takes about an hour.

  I say virtually indestructible, though you may as well say indestructible. Short of throwing them in a bonfire, there isn’t a good way to kill water bears. Water boils at 212 degrees Fahrenheit, but that’s like a nice day at the spa for these animals: They can turn the thermostat up to 300. Try boiling them in alcohol, you say? Won’t work either. Water bears can withstand pressures six times higher than in the deepest oceans, and you can bombard them with hundreds of times the radiation that would kill a human, and they shrug it off. In fact, when they were hanging out in space, some even got a dose of raw UV radiation, an extremely destructive energy when you don’t have the luxury of an atmosphere protecting you. Almost all perished . . . but a handful still survived.

  Perhaps most incredible, though, is the water bear’s resistance to cold. Absolute zero, −459.67 degrees Fahrenheit, is the lowest temperature possible. Well, technically nothing can ever get that cold, but in the lab, scientists can get close, the world record being one ten-billionth of a degree above absolute zero. When in cryptobiosis, the water bear can survive temperatures down to 458 degrees F, a degree and a half away from absolute zero. That’s even lower than the lowest temperature possible outside of a lab, about -455 F, which you’d only find out in the darkest, loneliest depths of the universe.

  HOW TO KEEP WATER BEARS AS PETS, OR JUST PRETEND YOU DO

  All right, you want one by this point, yeah? Good news: They’re in your backyard. Go grab some dirt, drop it in a petri dish, and add water. Put it under a microscope and among the many lovely organisms you’ll see swimming around will be pudgy little bears with eight feet. If you don’t have a microscope, you can still put dirt in a dish and pretend you have water bears. Up to you, really.

  Let that sink in. Th
e water bear is capable of surviving temperatures no organism would ever experience in the known universe, save for in a mad scientist’s laboratory. And that has startling implications for our conception of life. As a denizen of Earth, the water bear has it relatively easy. It’s got a nice atmosphere and lots of water and sunshine. But of course not all planetary bodies are so hospitable. Our own moon, for instance, has temperatures that fluctuate between −280 and 260 degrees F, easily tolerable for the water bear. There’s also all kinds of nasty radiation out there, which can scramble DNA. That’s a bit of an issue if you were hoping to pass down your genes—well, it’s a problem for most life as we know it, but not the water bear. It can repair DNA damaged by radiation. And if the water bear is so hardy, there must be other creatures out in the universe that are even hardier, inhabiting all kinds of weird, brutal environments we’d assume to be sterile. So looking for life elsewhere in space isn’t necessarily about finding another Earth. The water bear shows that life can take hold where you’d least expect it.