I keep Jeffrey II’s chrysalis on a living room shelf crowded with the abandoned nests of wasps and birds I’ve collected over the years. Light and dry as a piece of popcorn, the chrysalis is pale green with a thin line of yellow running top to bottom like a spine. Clinging to one side of the chrysalis is the tangle of silky threads Jeffrey II had spun to secure himself to the side of his terrarium, believing he was entering a dreamy metamorphosis that would take him from caterpillar to butterfly. Only the lentil-sized hole near the top, where his head would have been, offers a clue to his fate.

Of course, Jeffrey II’s name gives away the fact that he was not our first caterpillar. Before him, my husband, Mike, and I raised Jeffrey I. He also died long before becoming a butterfly, but in a different way. Had they lived, both Jeffreys would have grown up to be black swallowtails, their black wings dotted with yellow, blue, and red.

Two summers ago, I had no idea what a black swallowtail looked like. The only butterfly I could name was a monarch. And I’d certainly never given the idea of rearing caterpillars any thought. Then I met Jim, a monarch enthusiast I interviewed for a story I was writing about butterfly gardening.

He came to the door barefoot, trying unsuccessfully to gain control of his wild, wiry hair while sliding his feet into a pair of muddy rubber shoes he kept on the back step. Wide-eyed and fast-talking, Jim radiated the kind of wild enthusiasm common to people blessed with the ability to identify the amazingness of something and immerse themselves in it in a way that others will never understand.

I liked him instantly and tromped along behind him for nearly two hours while he showed me around his garden. On the porch he had several terrariums, home to monarch caterpillars and butterflies in various stages of development.

As we talked near a clump of dill, Jim suddenly shushed me, pointing to a swallowtail arching herself over a leaf to deposit three tiny eggs before flying off. It was something he’d probably seen thousands of times, but the sight took my breath away.

It had never occurred to me that caterpillars came from eggs laid by butterflies. I drove home wondering, “What else don’t I know about butterflies?” Soon my nightstand was piled high with entomology books and I learned all sorts of facts—some magnificent, others the stuff of nightmares. “Listen to this,” I would say to Mike before reading aloud. “Some male butterflies skip courtship and just rape females. . . . Apollo butterflies can actually smell the female virgins hiding in the grass.”

These are not the sorts of things my husband, a man who gingerly scoops up every spider he finds indoors before relocating it safely to the garden, wants to know about butterflies.

Me? I’m right there watching when my hero David Attenborough kneels down next to a pond and in that heart-melting British accent of his explains how diving beetle larvae are about to feast on a hapless tadpole by using their hollow jaws to suck out its juices. When it’s over, I tell Mike it’s safe to uncover his eyes and look at the TV again.

Naturally, it was Mike who first realized my summer obsession with butterflies was taking a dark turn. He said so one morning after I’d come in from checking on Harold, one of several black swallowtail caterpillars we’d adopted as our own the day I watched their mom deposit her eggs in my herb garden.

As always, I found Harold munching away on the yellow flower buds at the end of each dill stem. But his siblings were nowhere in sight. One by one, they had disappeared over the course of a week. It’s possible they’d all been snarfed up by birds or spiders. But I had a sneaking suspicion that wasn’t the case.

A quick Google search confirmed my fears. “I think he ate them,” I told Mike. “I think Harold is a cannibal.” I read on. “It says here they sometimes eat each other because they’re hungry or trying to thin out their numbers so predators won’t spot them.”

“If that’s the case,” Mike deadpanned. “We ought to change his name to Jeffrey . . . Jeffrey Dahmer.”

We continued to love Jeffrey despite his behavior. He kept up his endless cycle of eating, molting, and resting, and I sat on the ground beside him, tying each spent dill plant to the next fresh one so he could more easily lurch over to his next meal. I thought it was cute the way he ate each cluster of buds the way little kids eat candy. Grasping the stem in his dwarfish front legs, he single-mindedly chomped until there was nothing left. Then he lifted his head and looked around for more.

The more I read, the more we worried about Jeffrey. Most butterfly larvae never live to be become butterflies. Something usually eats them—a much better death, though, than being attacked by a parasitic wasp. Reddish brown and long and thin as sticks, parasitic wasps deposit their eggs in a caterpillar’s flesh. When the wasp larvae hatch, they devour the doomed caterpillar from the inside out.

Nearly three weeks after emerging from his egg, Jeffrey was now more than two inches long and a spectacular bright green, his slender body divided into doughnut-like segments painted with alternating dots of bright yellow and deep black. It wouldn’t be long before he would need a safe place to spin himself a safety net, curve his body into a J shape, and harden into a chrysalis. I hated to say goodbye.

I tried to move him to a less conspicuous spot in the garden, but every time I reached for him he would rear back like a cobra. Two skinny orange horns, scent glands, would come jutting out of his head. It was a nice trick, meant to scare off predators. But I didn’t want to engage my Jeffrey in a duel.

I called Jim for advice. He was surprised Jeffrey had lived so long right out in the open and said I should go buy a terrarium immediately to put Jeffrey in so he would be safe. Mike and I rushed to a pet store, returning with a nice, roomy terrarium with a mesh lid. I showed it to Jeffrey and then we hurried inside to eat a quick sandwich. Ten minutes later, we went out to move our little guy, determined to ignore his angry horns.

But he wasn’t there. “He’s got to be here,” I said, barely holding back tears. “I mean, what are the odds that something would have eaten him in those 10 minutes?” Kneeling on the ground, Mike was already pawing through the dill and running his fingers over the mulch.

We sat in the dirt for more than an hour, inspecting every plant. I fought the urge to kick the terrarium into the street.

He was gone. And then I spotted them, three tiny swallowtail larvae. I plucked the whole dill plant they were sitting on from the ground and put it in the new terrarium on the porch. I wasn’t taking any chances this time.

Three days later, only one of them remained. We named him, Jeffrey II. Still bereft over the first Jeffrey, we coddled his new incarnation as if he were a puppy. Summer was waning and dill was scarce in the garden so we took turns running to the farmers’ market to buy more. We put the fresh bundles in the terrarium and watched as Jeffrey II eagerly devoured them.

Unlike his namesake, Jeffrey II was easygoing and calm. We could move him without provoking his horns and we kept him company as often as we could. We’d read or eat our supper while he did his caterpillar thing in the shady, protected comfort of his terrarium.

Before long, he was as big as Jeffrey I had been before he disappeared. One morning, I walked outside and there he was, hanging from the top of the terrarium like a green and yellow candy cane, which quickly hardened into a chrysalis. I wondered whether it hurt to go through that.

After two weeks went by with no change in the chrysalis, I feared something was wrong. The books said that when the metamorphosis was nearly complete the chrysalis would be translucent. We would be able to see the outlines of Jeffrey II’s new wings. We stared. We waited. Another week went by. No change.

And then one morning we walked out with our coffee and something looked different. Near the top of the chrysalis we saw a small hole. And there, on the glass, was a wasp, red and glistening, catching its breath after having made a meal out of Jeffrey II while he waited for his butterfly life to begin.

Sobbing, I leaned down close to the wasp and told it that it would stay in that terrarium until it died too.

And it did.