Nature’s Villains?

OLD-SCHOOL NATURALIST-Notes from the Fields and Forests of Upstate New YorkBy Marlene McTigue

Nature’s Villains?  

Each summer, slender black wasps begin appearing around my front porch. They disappear into the tiny drainage holes in my metal chairs carrying blades of dried grass several times longer than their bodies. I’ve often found myself stopping whatever I’m doing just to watch them at work. Like most people, I assumed they were simply building nests.Then one day, one arrived carrying a tiny green tree cricket.At first, it looked dead.Then there was the slightest flick of one tiny leg.It wasn’t dead.It simply couldn’t move.I’ve spent enough time wandering the fields and forests to accept that nature isn’t sentimental. Even so, there are moments that make me stop and say, “Well… that’s horrifying.”I’ve learned that the closer I look, the more complex the smallest stories become.These were grass-carrying wasps (Isodontia), solitary wasps common throughout New York. The female hunts tree crickets, katydids and other similar insects, delivering an extraordinarily precise sting that paralyzes—but doesn’t kill—her prey. She drags the insect into a narrow cavity, lines the chamber with dried grass, lays a single egg, seals the entrance and flies away.Curiosity eventually led me to examine an abandoned nest tucked into a window casing. Inside were five or six tiny green tree crickets packed together like groceries in a shopping bag. Every one of them was alive. Every one of them was helpless.Several days later, the wasp larva hatches to find a perfectly fresh meal waiting exactly where its mother left it. Because the prey is still alive, it doesn’t spoil before dinner is served.It’s difficult not to admire the engineering while simultaneously feeling sorry for the tree cricket.Then there are the tomato hornworms.The first time I found one on my tomato plants covered with two perfect rows of tiny white capsules, I assumed it had picked up some strange fungal disease. I even considered removing it before whatever it had spread to the rest of the garden.Fortunately, curiosity got the better of me, and I did a little research.Those white structures weren’t growing on the hornworm at all.They were cocoons.Earlier, while you were quietly watering, weeding or harvesting tomatoes, a tiny braconid wasp had already injected its eggs into the caterpillar. The larvae developed quietly inside while the hornworm continued eating tomato leaves, apparently unaware that anything was wrong. When they matured, they chewed their way out, spun their little white cocoons across the caterpillar’s back and eventually emerged as adult wasps.In some species of parasitic wasps, the story becomes even stranger. Chemicals left behind by the developing larvae alter the caterpillar’s behavior. After the young wasps emerge, the caterpillar doesn’t wander away. Instead, it remains beside the cocoons, thrashing at predators and defending the very offspring that consumed it from the inside before finally dying itself.Think back. If you’ve ever seen a hornworm thrashing frenetically on a tomato plant, there’s a good chance you were watching one of these remarkable little life-and-death dramas unfold.If you think that sounds like something from an alien invasion movie, you’re not alone.Though it might not be your first thought, many gardeners welcome those white cocoons.Without predators like these, the balance begins to tip. Plant-eating insects reproduce astonishingly quickly, and without the countless hunters, parasites and pathogens that keep them in check, outbreaks can spread through forests, fields and gardens. Grass-carrying wasps help regulate populations of tree crickets, katydids and other small plant-feeding insects. Braconid wasps quietly suppress populations of tomato hornworms and countless other caterpillars. Multiplied across thousands of species, these tiny predators are part of an invisible workforce that has been maintaining healthy ecosystems for millions of years.Once you start paying attention, you begin to see these tiny life-and-death dramas everywhere around us. Meadows, forests and even vegetable gardens contain predators with hunting strategies so sophisticated they seem almost impossible. Some mimic scents. Some manipulate behavior. Some paralyze prey with surgical precision. Others turn living insects into carefully stocked nurseries for the next generation.It’s tempting to call them the villains of the insect world.Yet that judgment says more about us than it does about them.To the tomato plant, the hornworm is the villain.To the hornworm, the braconid wasp is the villain.To the tree cricket, it’s the grass-carrying wasp.Every story depends on who gets to tell it.Perhaps that’s one of the quiet lessons waiting for us in the fields and forests of upstate New York or maybe even in your own backyard. Nature has no heroes and no villains. It has only species, each following the same ancient script written long before people ever assigned the characters their roles.Nature doesn’t need us to like every character in the story. It only asks that each one be allowed to play its part.The next time I see one of those little wasps carrying a blade of grass across my front porch, I suspect I’ll still feel sorry for the tree cricket.But I’ll never look at the wasp quite the same way again.See you next week.