1 The First Rule of Zombification: You Do Not Want to Be a Zombie Wasps-aka the flying middle fingers of the animal kingdom-prove that evolution is the meanest and most beautiful thing the world has ever known. Nestled in a basement of Israel's Ben-Gurion University is Frederic Libersat's room of nightmares, a tiny box filled with still tinier boxes of cockroaches and the most conniving insect on Earth: Ampulex compressa, aka the emerald wasp or jewel wasp. Its hypnotizing beauty belies its belligerence, with big eyes and a precious green sheen to its body, colors shifting as the parasite sprints about the cage. Today is an unlucky day for this roach. It scrambles around a petri dish at the rear of the cage and seems to realize the mistake it's made. It freezes and rights its posture, like a tiny lowrider, but the iridescent wasp pounces anyway, grasping the roach and slamming her stinger between its front legs, paralyzing them. As the pair grapple in a Looney Toons-esque cloud of limbs and wings, the wasp, who's half the size of the cockroach, pulls out her stinger and-now unobstructed by normally flailing front legs-drives it through her victim's neck and into the brain. They keep tussling, flinging the cage's lovely pastel pebbles of blue and pink in all directions as the roach, desperate for leverage, braces itself against the wall of the plastic cage. Still the wasp, her body bent in half to make the reach, clings with her stinger stuck in the victim's head. But she's not dillydallying on account of pumping an ungodly amount of venom. No, she's feeling around for the right spot in the brain to inject her mind-control potion. Two spots, to be exact. While the combatants flutter, the wasp's ultradexterous stinger probes for a pair of regions in the brain that govern locomotion. When she finds them, she loads each with venom, releases her grip, pulls out her stinger, and backs away. And the cockroach . . . stands there. After a few more minutes, instead of panicking like you or I might if a needle just went through our brains, the roach begins grooming itself, taking its legs and antennae into its mouth. Calmly, systematically, one limb after another, like nothing happened. Ten minutes after the attack, the wasp again approaches. Without the slightest objection from the cockroach, she bites onto the base of its left antenna and slides her mouth a quarter of the way down, then snaps her jaws with a bob of her head. After a dozen tries-slide and bite, slide and bite-the wasp finally severs the antenna and laps blood from the stub. Then she does the same to the other-slide, slice, slurp. After all, brainwashing a cockroach takes a lot out of a wasp, and she needs to get back that lost energy. Still the cockroach does not object. When the wasp has had her fill, she again leaves the cockroach. But she returns a few minutes later, grabbing onto the left antenna stub and giving it a tug. Nothing doing-the roach won't budge. She leaves, returns, and tries again. The cockroach still won't follow. So she tries once more. This time the potion has kicked in, and the dupe is ready. The wasp grabs the cockroach by the antenna stub and starts yanking it toward a vial in the middle of the cage. And the roach follows. It could walk just fine in the other direction if it wanted, mind you, but it accompanies its diminutive captor through the opening of the vial and into its tomb without complaint. Here the wasp lays an egg on the cockroach's belly, then leaves and rummages around for those pastel pebbles, piling them into the vial. One by one, carefully she chooses the right-sized rocks to get a good seal. And never once does the cockroach try to force its way out-not that the wasp is plugging up the entrance to keep her victim in there. Instead, she's doing it to keep the neighborhood opportunists from consuming her prisoner. Inevitably the egg will hatch into a larva that pierces the roach's abdomen and sucks its blood. When that well runs dry, the young wasp will drill into the body and consume the organs, taking care to save the bits most vital for the roach's survival until the end-namely the central nervous system. After the tormentor has hollowed everything out, it metamorphoses, then erupts as an adult wasp from the cockroach's corpse, tunneling out of the tomb-turned-womb and into a world it will help make so cruel. At the risk of starting this book out on a negative note, I must say that nature is a terrible place. Not for you and me and a lot of other humans, mind you. But for every other organism out there, life is suffering. It's starvation, it's disease, it's a creature bigger and meaner than you chewing on your head. Even apex predators like lions and bears have to worry about their own parasites and food shortages and the ravages of drought. There is no dying peacefully in sheets with high counts. And the zombifying wasps prove it better than any other animal on Earth: Nature is not fun, and it does not care about your feelings or well-being. This doesn't bother me in a general kind of way. But watching the jewel wasp at work makes me sad. I have no love for cockroaches, believe you me. It's just how the parasite pounces and methodically drives its stinger into the roach's brain and lingers, with the victim's head bent in a silly way, staring at me through the plastic wall of the container. The cockroach doesn't speak English, and I don't speak Cockroach, but the idiot in me can't help but think it's asking for help. Which wouldn't do it any good because it's already too late. You know, the old clichZ of a zombie biting your friend and you having to leave them behind because you know the virus is on its way to their brain. Inevitably, the roach, too, will turn into a zombie. And not long after, a hollowed-out shell of an insect. Such suffering troubled Charles Darwin. The Christian view of the world in the nineteenth century was a peaceful one, with animals living in harmony on an idyllic planet tailor-made by God. But what Darwin realized was that the animal kingdom is one giant scrum, a frenzy of death and suffering, of teeth and claws and stingers. And it was the wasps-specifically the ichneumonids, which lay their eggs inside other creatures such as caterpillars-that really troubled him. "I own that I cannot see, as plainly as others do, and as I should wish to do, evidence of design and beneficence on all sides of us," he wrote in 1860. "There seems to me too much misery in the world. I cannot persuade myself that a beneficent and omnipotent God would have designedly created the Ichneumonidae with the express intention of their feeding within the living bodies of caterpillars, or that a cat should play with mice." The problem for caterpillars and mice and our cockroaches is that cruelty begets cruelty. Now, let me be clear that "cruelty" is a human construct. No creature but a human can find a wolverine chewing on its leg and think, "Wow, this is cruel." So yes, when I say that nature is cruel, I'm being a judgmental human. But what the wasps do to cockroaches and caterpillars is so very unpleasant because it's a tough world out there-no one is going to voluntarily babysit their young. Which means the victims are going to need some . . . convincing. This Might Sting a Little What Frederic Libersat is teasing apart in his little room of nightmares is a sting like no other on Earth. A snake might inject a mouse with venom that paralyzes muscles, most importantly those that keep the lungs breathing air and the heart pumping blood. But the jewel wasp's potion is far more intricate. That first sting paralyzes the cockroach's front legs so it can't bat away the wasp's brain-sting, sure, but the second sting doesn't paralyze the roach at all. Instead it sends the creature into what's known as a hypokinetic (meaning "below normal movement") state. The dupe can full well move, but it can't decide to, even as the wasp gnaws off its antennae and drags it into a dungeon where a larva consumes it alive. Libersat knows it can move because if you throw the stung cockroach into water, the stress will jolt it awake, sending it scurrying across the surface like a normal roach would. Which means its muscles work fine. "There's nothing wrong there," Libersat says. He looks like a slimmer version of Pablo Picasso, by the way, with shorn hair and eyebrows that bounce up and down his face when he gets excited. "It has really something to do with the animal engaging in walking, to make the decision that it has to move." With a head full of venom, and without the sudden stress of something like nearly drowning, it can only sit there for the wasp to torture. Why the roach would do such a thing is a big, complicated question that Libersat is just beginning to answer. But clearly, figuring out how a wasp can sting a cockroach in the brain to convince it to live the rest of its miserable zombified life as food for a larva begins with decoding that venom, which is composed of over two hundred different compounds. To start with, Libersat has found that it's loaded with a substance called gamma-aminobutyric acid, or GABA, which you'll find across the animal kingdom. This shuts down the front legs in that initial sting, but only for about five minutes. "GABA is a known inhibitory neurotransmitter in the central nervous system," Libersat says. "Basically what the wasp is doing is using existing machinery that produces this neurotransmitter." Meaning, the wasp didn't evolve some novel compound to cripple the cockroach-it weaponized the GABA that the roach and wasp share to short-circuit the muscles that power the front legs. When it comes to the brain sting, things get a bit trickier, considering this is, well, brain surgery. Why the wasp would want to force the cockroach to groom itself obsessively following the sting, or if there's any significance to it at all and it isn't just a bizarre side effect, is still a puzzle. But how the wasp makes it happen seems clear: dopamine. This compound is most famously associated in humans with pleasure-it's one of the reasons why cocaine is so expensive-but serves several other functions, including the regulation of grooming. Bump up dopamine levels in rats and you get more grooming, for instance. Humans, too, as it happens. "A drug addict has problems with dopamine," Libersat says, "because they take drugs that increase the level of dopamine, showing very often a stereotypic behavior of scratching, which is equivalent to grooming." Unfortunately for the cockroach, the wasp delivers a dose of dopamine-loaded venom not into the bloodstream, but straight to the central nervous system, leading to that same kind of obsessive grooming. Whether that serves to distract the cockroach, or if it's a way for the wasp to keep its host nice and clean and parasite-free (save for its own murderous larva, of course), or if, again, the behavior serves no benefit, isn't clear. But you can probably blame dopamine for it. Another tantalizing behavior of a stung cockroach is the way it carries itself, a phenomenon that Stav Emanuel, a postdoc in Libersat's lab, has been decoding. "They have decreased posture," Emanuel says. "The posture is weaker and their head is pointed down and their antennae are limp." It's the same kind of posturing you find in a sleeping roach. Not only that, but when Emanuel hooked up the leg muscles of stung and slumbering cockroaches to an electromyograph, or EMG, she found the electrical activity to be eerily similar between the two groups compared to their awake, unstung counterparts. So the wasp may have pulled off a brilliant evolutionary maneuver here. Much like it probably weaponized GABA-an inhibitory neurotransmitter it didn't need to bother inventing-to shut down the front legs, by stinging the cockroach in the right part of the brain the wasp may have also hijacked a preexisting state: sleep. Beyond the posture, a stung roach acts like a sleeping roach in that it's far less sensitive to stimuli, which may explain why it lets the wasp chew off its antennae and push it around. So by lulling the cockroach with a sting to the brain and erasing its self-preservation, the wasp can walk its much larger victim into the lair instead of having to drag it there. Here the roach sits dazed, unable to escape the larva that devours it alive. It's all reminiscent of the sleep paralysis you or I might suffer: You wake up and you're conscious, but your body is frozen. Only the cockroach's problem is it'll never snap out of it-that, and a larva is consuming it alive. Now, brain surgeons have their drugs, but they also have their instruments, and the jewel wasp's stinger is one magnificent tool. Any wasp or bee that stings you is a female, for that stinger is a modified ovipositor, which the insects use to lay eggs. (More dramatically put: The stinger makes life and takes life.) But unlike the brute force of a honeybee stinger-designed to drive into flesh and pump as much painful venom as possible-the jewel wasp's weapon is far more precise, a rapier to the honeybee's claymore sword. It's loaded with sensors that let the wasp feel its way as it penetrates the cockroach's neck and brain sheath and finally into those specific bits of the brain. Indeed, remove a cockroach's brain and give a jewel wasp the corpse and it'll feel around for ten times longer for the right spot to inject venom. Dip a wasp's stinger in liquid nitrogen and the manipulator gets even more flustered, feeling around for an average of twenty minutes compared to the typical sixty seconds. (Libersat did this by coaxing the wasp to sting through a film, like you would to milk venom from a snake or spider. But instead of extracting venom, he dripped liquid nitrogen on the wasp's needle.) If she can't feel her stinger, she can't feel the brain. So the wasp has stung its cockroach, crammed it into a den, laid an egg, and sealed it up. In this tomb the zombified roach loses its instinct for self-preservation, but a subtler manipulation is unraveling inside its body. Because unlike a snake, which immediately kills and consumes its prey, the mother wasp has to keep her victim unspoiled for a week, enough time for her larva to drain the life out of it and transform into an adult. Outright paralyzing the cockroach is a no-no-that'd mean it couldn't breathe. "No gas exchange means that the meat is going to rot quicker," says Libersat. So not only does the jewel wasp's venom keep the victim breathing, but it slows down the roach's metabolism. Meaning Mom injects a preservative of sorts to keep the roach plumper and fresher for her youngster. By turning a roach into a living larder, momma jewel wasp has evolved one hell of a way to help her kids survive. But why such cruelty? Why plunge a cockroach into such a nightmare? To answer that, we'll need to first explore the greatest idea that biology has ever known. Excerpted from Plight of the Living Dead: What Real-Life Zombies Reveal about Our World - and Ourselves by Matt Simon All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.
