by Mary Roach
Sign Here If You Exist
Jill Sisson Quinn
FROM Ecotone
THE FEMALE GIANT ICHNEUMON WASP flies, impressively for her near-eight-inch length, with the light buoyancy of cottonwood fluff, seemingly without direction, simply aloft. Despite her remarkable size, she is not bulky. Her three-part body makes up only about three inches of her total length, and is disproportionately slender; her thorax is connected to her abdomen by a Victorian-thin waist. Most of her maximum eight-inch span consists of an ovipositor half that length, which extends from the tip of her abdomen and trails behind her like a thread loose from a pant hem. Fully extended, she can be nearly as long as your Peterson's Field Guide to Insects.
Her overall appearance of fragility—the corseted middle, the filamentous tail—portrays in flight a façade of drifting. But both of the times I have seen a giant ichneumon wasp she was on a mission, in search of something very specific: a single species among the 1,017,018 described species of insects in the world (91,000 in the United States, 18,000 in Wisconsin, where I observed my second giant ichneumon). To comprehend this statistic, there are many things one needs to know: the definition of an insect, Linnaean taxonomy, the function of zero, the imaginary borders of states and countries. The female ichneumon wasp knows none of this. Yet it can locate a larva of the pigeon horntail—a type of wood wasp whose living body will nourish her developing young—hidden two inches deep in the wood of a dead tree in the middle of a forest.
Charles Darwin himself, it turns out, studied the ichneumon wasp. He mentions it specifically in an 1860 letter to the biologist Asa Gray, a proponent of the idea that nature reveals God's benevolence. Darwin, on the other hand, swayed no doubt by the rather macabre details of this parasitic insect's life, writes: "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"—and then, as if to reach the layman, he adds, "Or that a cat should play with mice." The tabby that curls in your lap and licks your temple, after all, has likely batted a live mouse between its paws until its brain swelled and burst. And the larvae of the giant ichneumon wasp eat, from the inside out and over the course of an entire season, the living bodies of the larvae of a fellow insect.
Like Darwin, I think I have put to rest my belief in a beneficent and omnipotent God—in any God, really. Contrary to what I once believed, it is easy to let go of God, whose essence has never been more than ethereal anyway, expanding like an escaping gas into the corners of whatever church you happened to attend, into the breath of whatever frightened, gracious, or insomnious prayer you found yourself emitting. But it is much more difficult to truly put to rest the belief in an afterlife, the kind where you might get to visit with all your dead friends and relatives. It will not be easy to let go of your deceased mother, who stands in her kitchen slicing potatoes and roast, who hacks ice from the sidewalk with shovels; she is marrow and bone, a kernel of morals, values, and lessons compacted like some astronomical amount of matter into tablespoons, one with sugar for your cereal, another for your fever, with a crushed aspirin and orange juice. You love her. You mark time and space by her: she is someone you are always either near to or very far from.
Can people live without the comfort of a creator? I think so. But relinquishing God—the Christian God, at least—does not leave everything else intact. A lack of the divine probably means that when you die what you consider your essence will cease to exist. You will no longer be able to commune with the people you love. Choosing to live without the assurance of an afterlife, therefore, feels like a kind of suicide, or murder.
Most parasites do not kill their hosts. You—your living, breathing self—are evidence of this, as you host an array of parasitic microbes. Only about 10 percent of the hundred trillion cells in your body are really your own; the rest are bacteria, fungi, and other "bugs." The majority of these microbes are mutualistic, meaning that both you and the microbe benefit from your relationship. A whopping 3.3 pounds of bacteria, representing five hundred separate species, live inside your intestines. You provide them with a suitable environment—the right moisture, temperature, and pH—and feed them the carbohydrates that you take in. They shoot you a solid supply of vitamins K and B12, and other nutrients. But some microbes, like the fungi Trichophyton and Epidermophyton, which might take up residence beneath your toenail as you shower at the gym, are parasitic—they benefit from you, but you are harmed in some way by them. In the case of these two fungi, you would experience itching, burning, and dry skin. But you've probably never heard of anyone dying from athlete's foot, because it has never happened. Successful parasites—parasites that want to stay alive and reproduce—in general do not kill their hosts.
The giant ichneumon wasp is one of a few parasites that break this rule. Actually, it is not a parasite at all; it is more correctly called a parasitoid because its parasitism results in the death of the host. This is not to say the ichneumon wasp is not successful. It can afford to kill its host because its host has a very fast reproduction rate. If we did not have the ichneumon wasp, we also might not be living in wooden houses, because the wood-boring insects that these wasps parasitize would probably have killed all the trees. The wasp might look formidable, but in terms of its ecological role, it is a friend to humans.
This is what it does: A new giant ichneumon wasp hatches from its egg in a dark, paneled crib deep inside a dead or dying tree where the pregnant female placed it. Nearby, or sometimes directly beneath the egg just deposited, lies an unsuspecting horntail larva that has been chewing its cylindrical channels in the wood for sometimes two years. The wasp baby latches on to the exterior of the caterpillar and feeds on its fat and unvital organs until both are ready to metamorphose into adults. Then, when the host has chewed the pair nearly to the surface of the tree, and the giant ichneumon wasp larva, which cannot chew wood, has a clear exit, the ichneumon kills and consumes its host. The wasp metamorphoses, possibly over the course of an entire winter, then emerges. Often before the newly metamorphosed females have even passed through their exit holes, they will mate with one of the plethora of males that have alighted on the bark for just this purpose. It's a kind of ichneumon quinceañera, a spontaneous debutante ball.
The problem of where I would go after I died began with simple arithmetic. In our family there were five—my mother, my father, my two older sisters, and me. Yet the world never seemed to divide by fives or threes as easily as it did by twos: I stood between the double sinks my sisters occupied when we brushed our teeth; the chair where I sat for breakfast, lunch, and dinner was pulled up to our oval table just for meals, positioned at a point not opposite anyone, and then pushed away when we were done—it didn't even match our first dining room set; I sat in the middle of the back seat of the car, while my sisters each got a window; and when we bought a dozen donuts, the last two always had to be divided, somehow, into five equal pieces—or three, which was no easier, if my parents were dieting. At some point in my childhood, for some unknown reason—I have asked them, and they still can't say why—my parents bought four burial plots. I couldn't make any sense of this. I worried. Where would the last one of us who died—probably me—be laid to rest? All I could foresee was my parents and sisters lined up neatly next to one another for eternity. All I could do was fear my impending, everlasting physical absence from the people I loved the most. Now that my sisters and I have married and they have had children and I have moved away, I realize the accounting error was not in buying too few but in buying too many: there will likely be two empty plots next to my parents. I've become accustomed to physical distance from my nuclear family by settling eight hundred miles from where I grew up, but the problem of where I will go after I die, what I will be like, and who will be with me has not gone away. It has only magnified.
Megarhyssa, the Latin name for the genus to which the giant ichneumon wasp belongs, translates to "large-tailed." The
species that I saw was likely the most common of the eighteen species of this genus, Megarhyssa macrurus, which translates to "large-tailed, long-tailed." These genus and species names, then, provide no information that an observer couldn't pick up in a single, fleeting interaction with the insect itself. The tail is more precisely called an ovipositor, an appendage used by many female insects—and some fish and other creatures—to place their eggs in a required location. That place might be soil, leaf, wood, or the body (inside or out) of another species.
The ichneumon's process of depositing eggs with her long ovipositor goes from mystical to complicated to bizarre. First, she locates her host by sensing vibrations made from its chewing beneath the wood. Her antennae stretch out before her like dowsing rods, occasionally tapping the bark, and she divines the presence of the horntail, catches it snacking like a child beneath the bed sheets who has made a midnight trip to the kitchen. She "listens" for the subsurface mastication of an individual caterpillar encapsulated in old wood.
Now the pregnant female begins the increasingly complex actions that will transport the eggs from her body through as much as two inches of woody tissue to the horntail's empty channel. Keeping her head and thorax parallel to the wood, which she grips with her legs, she first curves her abdomen under, into a circle, touching its tip to her thin waist. Her ovipositor, as if its outrageous length were not surreal enough, now performs a magician's feat: it separates into three long threads. The center one is the true ovipositor; the other two are protective sheaths that will help steady the insect's abdomen and guide the ovipositor as it enters the wood. (When she is finished laying and flies off, you will sometimes see these three threads trailing separately behind her.) The two sheaths, one on each side, fold back and follow the curve of her abdomen, then come together again at the very tip of her thorax and head straight for the wood, sandwiching her body in two broadly looped capital Ps. The ovipositor extends directly into the two sheaths where they join and disappears between them. In order to allow the ovipositor's acrobatics, the exoskeleton at the tip of the abdomen splits somewhat and pulls back. At this stage in her laying, with her ovipositors perpendicular to the tree, her wings flat and still, and her legs spread-eagle, the ichneumon looks as if she has pinned herself to the wood as an entomologist might pin her to a cork for observation.
Before we hang up from our once-weekly phone call, my mother says she has one more little story to tell. This one is about Kristen, my niece, at age five my mother's youngest granddaughter.
The week before Easter, she and Kristen drove to the church where my grandparents and my mother's little brother, who died when he was a baby, are buried. My mother wanted to put flowers on the headstones. Before they got out of the car, Kristen began talking about her own mother and her older sister, Katie.
"Mommy and Katie want the same," Kristen said, "but I want to be different."
"What do you mean?" my mother asked.
"I want to be buried," Kristen replied. "But Mommy and Katie want their bones..." She paused for a minute, thinking, then continued. "They want their bones burned." Kristen paused again, then concluded, "But, really, I don't want to die."
My mother said she had to stifle a laugh. And I laughed, too, when she related Kristen's words. Yet I can't help but think our laughter was cover for some deeply rooted disquiet. It's merely the brain's best method for dealing with this cruel yet basic fact of life—that it ends—stated here so rationally by a little person just in the process of recognizing it.
My mother, always prepared for the teachable moment, put forward to Kristen, "Well, Jesus is going to give you your body back, you know."
Kristen was not appeased. "That's weird," she replied.
The very intricacy—and weirdness—of the ichneumon's egg laying makes it difficult for most of us not to wonder who came up with the complex series of steps involved. Part of that is because humans seem to be, as professor of psychology Paul Bloom puts it, "natural-born creationists." His essay "In Science We Trust," from the May 2009 issue of Natural History, posits that where humans see order—anything that is not random—we immediately assume that an intelligent being has created that order. Bloom sums up the research beautifully: children aged three to six who were shown pictures of both neat and messy piles of toys, along with a picture of a teenage girl and a picture of an open window with curtains blowing, reported that both the sister and the wind could have caused the messy pile, but only the sister could have stacked the toys neatly; likewise, shown a cartoon of a neat pile of toys created by a rolling ball, babies as young as one year old stared longer than normal, which, according to developmental psychologists, indicates surprise.
I once found at the mouth of a sizable hole along a favorite trail a mashed garter snake, a flattened mole, and a deceased opossum. They were each uneaten and—I knew intuitively—could not possibly have all died there coincidentally. Rather, I soon found out, they were a stack of "toys," planted neatly by a mother and father fox at the den entrance, to occupy their kits in the dusk and dawn while the parents hunted and scavenged for food. (When the family moves to a new den, which they frequently do, the parents will actually move the toys as well.) A pile of sticks pointed on both ends, with the bark removed to reveal the white wood underneath, mortared together with mud and lined up across a stream, has never been the work of the wind in the entire history of the earth, but always the work of an intelligent being— Castor canadensis, the American beaver.
But being "created" does not inherently imply the existence of a creator, as evidenced in Darwin's work on Natural Selection. Bloom explains, "Darwin showed how a nonintelligent process driven by random variation and differential selection can create complex structure—design without a designer." So this instinctive assumption that complexity is the work of an intelligent being is true most, but not all, of the time.
Natural Selection, though, in itself, does not inherently negate the existence of a creator. It is possible to imagine that a creator put into motion several set laws—the laws of Newton, for instance, and the laws of Natural Selection—then, without interfering, let creation unspool itself.
But even this belief begs a question. I asked my mother this question once, when I was seven or eight. We were in the car, on the way home from my organ lesson. "What was there before God?" I asked. "Who created him?"
"There was nothing," my mother said, and her hands left the steering wheel for a moment. Her fingers spread, like the fingers of an illusionist, as if she were scattering something, everything in the known world, I guess. These religious discussions of ours were delicate and infrequent, almost, like discussions of sex in our family, too intimate to occur between parent and child. When we did have them, it felt as if we were too close to uncovering something—for her, something too hallowed to be near; for me, something possibly too tragic. "I know," she conceded, "it's hard to imagine."
But I did imagine it, using the only sequencing skill I had then: a two-frame comic strip. In the right frame there was a profile of a cartoon God, and in the left frame just blackness.
Megarhyssa macrurus is a mixture of mustard yellow and auburn, with chestnut brown accents. From a distance, the wasp may look just dark, but pinned, as the female is during egg laying, and patient, as the male is when waiting for the virgins to emerge, you can easily get close enough to notice the mostly yellow legs, yellow-and-auburn-striped abdomen, and brown antennae and wing veins.
When the female is well into her egg laying, and possibly at the point of no return, she becomes even more colorful and, at the same time, more bizarre. We left her with her three tails separate and in position, and her abdomen curled in a downward circle. Once it is time to deposit the eggs, she uncurls and raises her abdomen so that it is nearly perpendicular to the tree and her body. Her tails remain in their same positions. But two of the segments near the tip of her abdomen open wide, like the first cut in an impromptu self–cesarean section, revealing a thin yellow membrane. The membrane, tau
t like the surface of a balloon, is about two centimeters in diameter. It pumps gently. It is as attention-getting as a peacock's display, but wetter, more intimate. Within that membrane you can see what look like portions of the ichneumon's three tails as they exist inside her body. Though the ovipositor appears to begin at the tip of her abdomen, as an appendage—like an arm or a leg or a tail—it must in fact be more tonguelike, and extend into her inner recesses. It's as if you're witnessing an X-ray, but even so, it's very difficult to figure out exactly what is going on. There are too many parts, too many steps, too much intertwining. Watching the ichneumon lay her eggs is like trying to decipher one of those visual-spatial problems on an IQ test: if the following object is rotated once to the left, and twice vertically, will it look like option A, B, or C? Give me the 3.5 billion years that Natural Selection has had—whether here or in the afterlife—and I just might figure it out.
Belief in an afterlife, and the manner of behavior, prayers, rituals, and burial practices necessary for navigating one's way to it, can be considered a universal in human cultures. But belief in an afterlife cannot be considered the essence of all religions. Certainly there were cultures obsessed with it—the Egyptians, for instance, who took part in elaborate processes of mummification in order to preserve the dead and aid them in making the physical journey to heaven. But, hard as it may be for Christians, for whom a belief in resurrection and the afterlife takes center stage, to understand, other cultures and religions either simply didn't address the afterlife or had a less-than-attractive view of it. Those who originally penned the Hebrew Bible, for example, did not conceive of any type of survival after death; God harshly punished those who did not listen to his Word in this life with plagues, fevers, famine, and exile, and rewarded those who did with immortality only through their physical descendants. Were Natural Selection an option for the early Hebrews, I believe they would have been more accepting of the theory than today's Americans.