The Wasp That Brainwashed the Caterpillar

by Matt Simon

  Duck genitals: Fascinating Americans, other than 89 percent of Fox News viewers, since 2005.

  So, sure, we human men may not always have the greatest ideas, but at least we’re not penis-fencing. It’s the little things that count, really.

  Mustache Toad

  PROBLEM: Competition to win the affection of females can be intense.

  SOLUTION: If you’re a certain kind of male toad, you grow a mustache with which to shank your rivals.

  “The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick,” Charles Darwin once wrote to the American botanist Asa Gray. He despised the peacock’s flamboyance, for it seemed to be a living, prancing affront to his theory of evolution by natural selection. He agonized over how something so heavy and conspicuous could make a creature anything more than vulnerable. But Darwin eventually realized the tail’s ability to attract females outweighs its risk of getting the owner killed: sexual selection. The peacock is a tasty creature with a giant target sprouting out of its bum, but it’s also a sexy creature with a giant target sprouting out of its bum.

  But for other horny fellas out there, such foppishness seems a luxury. Sometimes the right to mate is won not with towering feathers but with much bloodshed and broken bones and maybe even a ruptured organ or two. A male’s mad pursuit of passing along his genes sometimes overrides the risk of bodily injury.

  There are few creatures that go about it all more fashionably than the mustache toad, whose name speaks for itself. The thing is horny. Just as male deer shed and regrow their horns to battle each other every mating season, so, too, does the toad develop its own weapons: ten to sixteen extremely sharp spikes situated along its upper lip. Known as nuptial spines, these lances are made of keratin, the same stuff that makes up your hair and fingernails. And they grow right through the toad’s skin. With these spines the toads engage in hyperviolent battle with other males for prime mating spots.

  Now, these toads are terrestrial creatures, but each year they return to the water to mate in an event epically known as “explosive breeding.” Competition to mate is daunting, as toads from all around begin gathering for their three-week sexy season, with ideal mating spots being underwater. If you were a smart mustache toad you’d be looking for a nook with an overhang, a spot where you can best guard your developing young. This makes breathing a problem, since coming up for air is risky when there are plenty of other gentlemen that would steal a good base of operations. But the toad has an ingenious, flappy solution: Its skin gets loose and wrinkled in the mating season. That may seem like a glaring inconvenience and certainly not a solution at face value, but it boosts the creature’s surface area. And because toads can absorb oxygen right out of the water, more skin means better breathing and less frequent trips to the surface.

  Inevitably, though, the squatters will face challengers. The battle begins with some good old posturing, as the defender tries to block the entrance to the den while vocalizing. But the challenger’s having none of it. He attacks, and the two come together like flabby-skinned sumo wrestlers, grappling and shoving and squirming. The scrappers start stabbing, both trying to get their snouts under their opponent so they might heft each other up. If one of them succeeds, he’ll lift his foe vertically, still holding tight, and proceed to shank him in the belly while slamming him against the walls of the den.

  While the foes may have loosened skin, it does little to protect them from the trauma. Getting laid is great, but getting killed in the process doesn’t help the cause, so the weaker toad flees, exhausted and poked full of holes. In the end almost 100 percent of the combatants will end up injured in some way. But the stakes are too high not to fight for a cave: Females are sizing up not just a mate, but his den as well, since he’ll be taking care of the kids while she absconds. When she comes along, there’s a bit of nudging with the victor, and a bit of swimming around checking the place out, and finally the sexy time. He grasps her, and while she lays eggs, he fertilizes them and sticks them to the roof of the den with his foot. She then splits, while the male remains, rubbing up against the eggs to keep them clean until they hatch and swim off as tadpoles.

  ALL RIGHT, WHICH ONE OF YOU KNUCKLEHEADS NAMED THE IRISH ELK?

  The mustache toad may have great facial hair, but its weapons are like Tinkertoys compared to those of the Irish elk, which went extinct just eleven thousand years ago. The animal wasn’t confined to Ireland and was actually a regular deer, not an elk, but it did have the biggest antlers of any animal ever to live. With antlers twelve feet wide, you can only imagine the toll these things took on their owners, and in fact that may have helped do the awe-inspiring Irish elk in. As their habitat began to cool, the food supply dwindled, a problem of particular severity if you’re in possession of twelve-foot-wide horns that you need to feed in order to regrow every year.

  If they haven’t snapped off in combat, the nuptial spines will fall off on their own as the toad returns to land and a life of relative peace. And I really can’t overstate what an amazing commitment the whole adventure is for the males. On top of holding their breath and hanging out in caves for the three weeks of the breeding season, growing and shedding spines out of their faces year after year is a huge drain on resources and energy. But again, the stakes are too high to not participate in the strange rumpus.

  APPARENTLY NECROPHILIA IS “SOCIALLY UNACCEPTABLE”

  The females of another species of frog, Rhinella proboscidea, don’t get off so easy when it comes to mating. These frogs are also explosive breeders, with hundreds amassing in a single pond. In the frenzy, many females will drown, but that’s not about to stop the males. They’ll massage a dead female’s belly to eject her eggs, then fertilize them. It’s called functional necrophilia, because why not. In one paper on this bizarre ritual, scientists found it necessary for whatever reason to note that this ranks among the reproductive behaviors “that are considered ‘socially unacceptable’ and impossible in human society.”

  At the very foundation of all this is the raw fuel of evolution: variation. When two parents come together, their offspring vary not only because their two sets of genes combine in unique ways for each kid (save for identical twins, of course), but because mutations can sneak in. These mutations can be either harmful, inconsequential, or beneficial to the organism. So a mustache toad isn’t just an exact copy of the previous generation—at some point long ago, male toads with mutations that gave them mustaches started showing up, and because that trait afforded them a competitive advantage to win mates, they got to pass along the genes responsible for the spines. And winning mates is only one consideration here. Traits that help organisms eat in turn help them survive to pass their genes along. Traits that help them avoid predators do the same. Thus species evolve to fit their environment, skirt their enemies, and earn the right to mate.

  And thus things get a bit carried away sometimes, resulting in adaptations like weaponized mustaches. But there’s no guiding hand here, just a step-by-step transformation of an ordinary toad into an amphibian Tom Selleck.

  Toadfish

  PROBLEM: As with the mustache toad, fish sometimes have to win the right to mate.

  SOLUTION: Fighting is for simpletons. Instead of brawling, toadfish males use their swim bladders to attract females. They produce a hum so loud that the mysterious noise once drove houseboat residents in an American town to madness and led to a full-scale investigation.

  The year was 1985. The locale: a seaside community called Sausalito just north of San Francisco, where houseboats bob and sometimes a sea lion shows up, much to the delight of tourists. The problem: a maddening, perhaps excruciating hum on summer nights that some said was the work of aliens. Others fingered the government, and still others the nearby sewage plant. The curious editorial headline to mark the occasion in the Marin Independent Journal: “Do lovesick fish sing in Sausalito?” The paper’s answer was an emphatic no.
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  But the paper was wrong. The town had in fact fallen under the spell of a mating song—the toadfish’s, to be exact—a sound that defies human credulity. It’s reminiscent of a bassoon, or an extremely loud swarm of bees. An official complaint from a houseboater described it as a noise “similar to having an airplane in your house,” which in retrospect may have been a bit hyperbolic. The clamor is a bummer for humans, sure, but really the male toadfish has no choice in the matter. It needs to attract females, who choose only the boys with the most impressive bellows.

  WHO ARE YOU CALLING A LYRE?

  No offense to the toadfish, but when it comes to mating songs, nothing on Earth can beat that of the lyrebird. When vying for the affections of the ladies, the male will pop his resplendent, almost peacocklike tail feathers over his head and prance around, all while belting an astonishing tune. It’s part sci-fi laser, part high-pitched plucking of strings, and part impressions of other birds in the forest. In captivity, though, he’ll imitate the surrounding cacophony: car alarms, drills, and hammers (if he’s in a zoo that’s undergoing renovations), even camera shutters. It’s all done so perfectly that it boggles the mind. At the risk of tearing you away from this here book, you should go find videos of the lyrebird. I mean it. It won’t hurt my feelings.

  The word spilled out of Sausalito and went national. On the CBS Evening News, Dan Rather was in a state of disbelief, declaring that if you think that a fish could produce such a din, “you believe frogs have hair.” (It turns out there is indeed a species called the hairy frog, whose males have hairlike projections of skin that, like the mustache toad’s loose skin, help them breathe underwater while guarding eggs—but whatever.) The Marin Independent Journal’s editorial was similarly unrestrained and seems to have been the work of either satirists or the functionally insane, or perhaps both. The paper noted the timeliness of the noise—generally from nine p.m. to five a.m.—and asked, “What self-respecting fish keeps a schedule?” They added, no joke: “Only the species that developed the atomic clock, the digital watch and the on-time European train is capable of creating such a commotion at the same time night after night.”

  The man who set off this hullabaloo was one John McCosker, a legendary biologist at the California Academy of Sciences in San Francisco. So, he tells me, one day back in the eighties he got a call from a noise specialist in the health department, which had been investigating Sausalito’s racket and spending a good chunk of change in the process. They’d run out of viable theories, and the last and least likely on their list pegged the hum as biological in origin. McCosker had the guy play a recording over the phone, and without hesitation he identified the racket as the product of Porichthys notatus, the toadfish.

  “Jesus Christ,” McCosker recalls the man saying. “Don’t. Tell. Anybody. Because we’ve been going all the wrong places trying to figure out whether it was the sewage plant or the Army Corps, and all of these people are really pissed off about it. I didn’t know a fish could make so much noise.”

  The good people of Sausalito weren’t buying it. What they had a hard time coming to terms with is that the ocean is an incredibly noisy place to be because sound travels very well in water. Humpback whales, for instance, sing thundering songs that last as long as a half hour, communicating with each other across entire oceans. All manner of fish and porpoises are breaching, slapping the surface of the sea. The waters themselves are in an uproar, as tides and currents and upwellings from the depths clash, even far from shore. As marine biologist Rachel Carson once described it in her classic book The Sea Around Us: “Superficial hissings and sighings, the striping of the surface waters with lines of froth, a confused turbulence and boiling, and even sounds like distant breakers accompany the displacement of the surface layers by deep water.” Thus water and creatures conspire to produce cacophony. Perhaps it was McCosker who put it best in a 1986 paper: “It is my view that the Bay Area yuppie invasion comprises a generation that has all but forgotten the noises of nature—like crickets, frogs, cicadas, and toadfish. Damn shame.”

  The toadfish male’s trick is a gas-filled organ called a swim bladder, which helps fish maintain neutral buoyancy. By controlling how much oxygen fills its swim bladder, the toadfish can avoid constantly adjusting up or down with flips of its fins, thus saving energy. (Sharks, famous for energy conservation, use a similar method, but they don’t have a swim bladder. Instead, they maintain their position with the help of their giant liver, which may make up as much as 25 percent of their weight.) The male toadfish can vibrate the muscles that attach to the resonating chamber as many as 150 times a second, producing a hum that drives the ladies—and humans in the houseboats above it—mad.

  THEY DON’T MAKE CONDOMS LIKE THEY USED TO, AND THAT’S FANTASTIC

  Fish bladders aren’t useful just for fish. European gentlemen once used them as condoms. From a 1908 sales catalog: “Fish bladders are preferable to rubber since, being significantly finer and more durable, they are not as obtrusive as rubber, and the sensation is hardly affected if at all.” These things were really expensive, being the ultrasensitive rubbers of their day, and accordingly conscientious gentlemen would wash them after each tryst and reuse them. So it would seem that while the swim bladder has helped the toadfish make babies, it’s also helped humans avoid making them.

  Yet not all male toadfish hum. The males are split into two types: an alpha variety, which actively hums for females, and a so-called sneaker variety. The alphas are eight times larger than the sneakers and have swim-bladder muscles that are six times as big. The sneakers, though, have the alphas beat on testicle size, sporting gonads that are seven times as large as those of their counterparts.

  But why? Well, the alphas maintain nests on the seafloor, and they sing and sing and sing, for perhaps as long as two hours straight, with those big, highly developed muscles powering their swim bladders. The females they manage to woo will approach and drop off a batch of eggs, and the alpha will fertilize them and continue to look after the developing young. But a sneaker male will lie silently in wait nearby, then dash in and fertilize the eggs himself. And it’s here where those big testicles probably come into play: The sneaker may get only one chance at fertilizing a clutch, so he wants to produce as much sperm as possible in a go. The alphas, by contrast, invest more energy and resources into growing giant to defend their nests. But the sneaker avoids devoting energy to all of that stuff—growing outsized, building a nest, calling to the females, and looking after the eggs once they’re fertilized. Thus the genes that make for a clever sneaker toadfish persist through evolutionary time, however precariously alongside the pissed-off alphas that are doing the actual work.

  And evolutionary time is a whole lot of time, so why did the toadfish’s love song suddenly become a problem in Sausalito in the eighties? Where had they been all along? Well, they were there, all right, but in plummeting numbers. During World War II, a nearby shipyard was churning out war machines, and lots and lots of nasty chemicals along with them. The bay was a mess, and the fish suffered for it. But then cleanup crews went to work, McCosker says, “and did some dredging and stopped putting all of the spoils in there, and more fish starting coming in.” The Sausalito yuppies, and their admirable environmentalism, had ironically enough been responsible for the racket all along.

  After McCosker’s revelation, disbelief gave way to acceptance, and for a while the residents of Sausalito held a toadfish festival. That’s gone now, but the toadfish remain, humming their love song as the houseboaters above wonder how big a war it would take to get that shipyard rebuilt.

  CHAPTER 2

  You Can’t Find a Babysitter

  In Which Caterpillars Give Horrific Birth to Maggots While Other Caterpillars Give Stylish Birth to Hairdos

  Thank your lucky stars you’re a mammal, and thank them again that you’re a primate whose mother could cradle you and cart you around. We humans look after our young, but few other anima
ls have such luxury. So in the absence of babysitters, they rely on other strategies to ensure their kids survive. Some just throw a lot of offspring into the ecosystem and hope a few make it, while others get rather more creative with the whole thing. As in, injecting their young into other animals and passing off the responsibility. So, again, thank your lucky stars.

  Ant-Decapitating Fly

  PROBLEM: Maggots are helpless. And that can be an issue if you’re a maggot.

  SOLUTION: The ant-decapitating fly surgically inserts its kid into a living ant, where the maggot moves into the brain and mind-controls the host into the leaf litter, before releasing a chemical that pops the ant’s head off. Safely inside, the maggot develops like a babe in a crib.

  If evolution by natural selection is the greatest idea anyone has ever had, its discovery is surely one of the more stunning coincidences in the history of human thought. Good Old Charley Darwin gets all the credit, but the aforementioned Alfred Russel Wallace had not only simultaneously developed the same theory, but had arrived at it, at least in part, by the same inspiration: Thomas Malthus’s “Essay on the Principle of Population.” Malthus argued that if the human race didn’t keep its population in check, it’d have the checks placed for it in the form of war and famine and intense competition for resources. Both Darwin and Wallace realized that the same is going on in nature: Species have more offspring than can survive, and predation and limited food pare them down and keep them in check. Siblings vary, so the ones with the beneficial variations survive and pass down their genes, driving evolution.