I spent a lot of time in my garden this past summer. 2020 has easily been the strangest year of my life thus far. With each passing day, everything seemed to spin faster and faster out of control: a global pandemic with a rising death count, a nation facing a racial reckoning, a looming presidential election, and an economy teetering on the brink of collapse. Everything felt so chaotic, and yet each morning the sun would peek out of the horizon in the east and and slip slowly across the sky to set in the west. The seasons advanced with new spring buds expanding into dark green foliage. And the seeds we tucked in under a blanket of soil sprung to life with spring rainstorms and soft sunlight. The natural world continued, steadily onward. The Earth was not oblivious to the turmoil. She felt a brief reprieve as we slowed our fossil fuel emissions and the sky cleared. She sensed the outcry as we took to the streets and demanded justice. With the spring she awoke and began to provide us with the nourishment and the light we needed to march forward through the chaos.
I accepted the Earth’s gifts of sunlight and green growth with gratitude and humility as I sat in the garden, sometimes pulling out weeds, sometimes collecting ripened food, and oftentimes just watching. I first spotted one of her gifts as I stood with my hands tangled in an unruly jungle of carrot tops: a couple of caterpillars swaying in the greens. Their skin blended in with the leaves they were munching, so it took me a moment to notice, even as I pushed the tops back and forth in my search for another orange carrot ready to tug out of the ground. Thanks to the wonders of modern technology, I was able to bypass the stack of worn field guides spilling out of the chest in our living room in my quest to identify these caterpillars. A few clicks and a Google search later, I had learned that my mysterious garden guest was the larvae of an eastern black swallowtail, or as many people refer to it: a parsley worm (Papilio Polyxenes).
With their yellow spots, the larvae do have distinct markings, but it was their choice of food that gave away their identity. With a hankering for food in the carrot family (Apiaceae), like parsley, carrots, dill, celery, caraway, and fennel, they’ll enjoy your garden produce nearly as much as you do. For the caterpillars roughing it in the wild, they may select Queen Anne’s lace (Daucus carota) or poison hemlock (Conium maculatum).
The black swallowtail larvae go through a series of costume changes in their young lives. After they hatch from eggs, they are in the first instar phase, or the period of an insect’s life before it molts and enters the next phase. Brown and spiny with a splotch of white on its back, it is hard to believe the first instar and the last are even the same insect. But as they grow larger and shed their previous exoskeleton ensemble, they develop into a caterpillar with smooth green skin striped with black and marked with yellow spots.
They only reach roughly two inches in length, so the caterpillars have to use other means of defense. When disturbed, they will extend their osmeterium, an orange, horn-like organ from just behind their head. When protruding, it releases a smelly chemical meant to repel predators. The intended effect is perhaps lost on humans who rarely see more than a cute, angry little caterpillar, and it certainly doesn’t help them fend off the pesticide some people apply to remove them from their garden.
With the transformation of the body they also go through a transformation in the minds of humans. The caterpillars are called parsley worms, and the connotation is quite clear; they are often considered bothersome garden pests. And yet, most people would never consider dousing pesticide on the beautiful black swallowtails, which in addition to being lovely are also important pollinators. We spend so much time obsessing over the flaws that fail to appreciate the potential.
I loved seeing the black swallowtail butterflies fluttering about in the summer, and the idea that a new generation was developing right before my eyes was exciting (even if they took the carrot tops with them). As September approaches, the mature larvae move off of the garden plants and prepare for the pupal stage, during which they transform into butterflies. Some choose plant stems, tree trunks, or even man-made structures to undergo their transformation. For one little caterpillar, a small, ground-level window on my house was the place of choice.
The green caterpillar spun two thin pieces of silk and attached itself to the upper corner of the window frame. It then shed its exoskeleton one last time to reveal a chrysalis, which is the pupa’s hardened, outer case. For the black swallowtails that are overwintering, they will spend months in this chrysalis in a form of hibernation called diapause. Other species, like monarchs, may migrate away to warmer climates for the winter, but black swallowtails put their resilience to the test. They hunker down to wait out Wisconsin’s long bitter winter, and with the welcoming warmth of spring they emerge from their chrysalis completely transformed.
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