Breaking A Butterfly Upon A Wheel: Why We Hate Caterpillars But Mourn Pollinators

July 20, 2021

Who breaks a butterfly upon a wheel? Or demonizes a hungry caterpillar for its 200-million-year case of the munchies?

Tobacco Hornworm

The family of Sphinx Moth caterpillars, the hornworms, trigger the wrath of gardeners everywhere.

Entomologist and author Dr. David Wagner is a smart guy who likes caterpillars. They are, he recently told me via Zoom, essential to life on earth. He’s currently studying and reporting on global insect decline as a crucial biomarker of what may lie ahead for our planet unless we intervene against deforestation, Big-Ag intensification, desertification, climate change and ocean acidification, among other grave planetary stresses.

“The proverbial canary in the coal-mine may not be a canary after all,” he said. “It may be the hornworm in your tomato-patch.”


My grandmother always grew a tomato. It was often just a single spindly plant or two in a decapitated water jug, perched on the fire escape outside our fourth-floor apartment. One Saturday morning, I looked up from my Latin homework to see something amazing where the tomato plant had been the day before. There it was: a caterpillar the size of a Hebrew National hotdog, translucent as jade, reared up into a majestic green question-mark pose, and not a tomato leaf or bud remaining in sight.

Aye-e-e-e-e-e!” exclaimed my grandmother as I carried it to the kitchen table, arched on its now-bare stick. “Get that monstah outta here!”  She threatened to flush it down the toilet, where it could feed New York’s apocryphal alligators. As we argued, the caterpillar, a hornworm, calmly dropped a grooved, green pellet—a fresh turd—onto the open page of my catechism workbook. “Now it’s blaspheming!” she gasped, lifting her foot out of her chancla (and we all knew what that meant).

Luckily for all, I prevailed. I took my baby-sitting, leaf-raking and snow-shoveling money down to the Bodega Victoria, where Mr. Perez let me have his last two scrawny tomato plants for $2, giving me what he always called the Victoria discount. I improvised a droopy hornworm habitat using a shoebox of curbside dirt, topped with the gauzy frill from the shower-curtain (a costly design decision). Every night as we fell asleep in the bedroom we shared, my grandmother would say, “I can hear it chewing. That thing is giving me nightmares.”

The caterpillar scarfed down the first two plants and several more, swelling and arching before dropping to the dirt floor of its tented home. By flashlight one midnight, I watched it burrow down into its box of native Bronx grime and soot, and disappear from sight.

“Oh! It’s gone? Thank God,” my grandmother said the next morning, sweeping the contraption into a big black garbage bag from the bureau where a glow-in-the-dark statuette of the Blessed Virgin Mother had stood guard. I secretly rescued the box while my grandmother napped, and placed it on the fire-escape, where I resumed the vigil—literally a Hail Mary pass for our barely tolerated intruder.

Then I passed my catechism, and was confirmed. Nothing much seemed to be happening in the realm of tomatoes. The summer night seemed bland and warm when I heard un grito from the fire escape. A wet, plump, thrashing something had landed on my grandmother’s newspaper, brazenly squirting brown fluid all over the Bodega Victoria coupons page. It was a newly emerged adult Sphinx moth, Manduca quinquemaculata, the five-spotted, end result of the green worm everyone (but the few, the proud, the brave) loves to hate.

The moth fanned its wings as they stretched and dried into shape, and then fizzed off into the smoggy dusk. My grandmother turned to me in wonder: “Is that how that thing got up here? It flew up all four stories, just to find my tomato?” Then she confessed she had been using its shoebox home as her ashtray.


My love of sun, seeds and dirt now finds me on the opposite coast in a couple of gardening groups. I’m learning a lot at The Posh Squash, starting with Rule #1: never piss off a vegan.

Mushroom Ed as he’s known, a teddy bear-ish retired attorney who resembles Dr. Andrew Weil, is red-faced, fists clenched, as he surveys fresh damage to his plants. “S-S-S-S-S-ATAN!!!” hisses Julie Sunshine, the de facto mayor of The Posh Squash. She’s aiming her trowel at the large green hornworm that has munched its way through her first fruits.  It’s a choice specimen of the Tobacco Hornworm that loves to eat tomatoes, a little critter with major BDE.

Speaking of BDE, Jonathan Lawler (@RealPunkFarmer) frequently sounds off on hornworms: “They can bite, but screw that…smash them into oblivion! Burn them, stab them, impale them. Unleash pure unadulterated violence on these invasive hell spawns.” (In Lawler’s defense, his non-profit Brandywine Creek Farms donates thousands of pounds of fresh produce to food banks, food pantries and community centers. Self-described Ag-Activist Lawler and his wife Amanda also create numerous job opportunities for at-risk youth, formerly incarcerated individuals and people recovering from addiction, and they’ve helped to create 5 large urban farms in Indianapolis.)

The variety accosted daily in the Posh Squash is Manduca Sexta, so named because the adult moth will bear six spots on its sturdy abdomen—but only if the creature manages to survive its dangerous, sun-filled days before descending, Persephone-like, below the earth’s surface for a chthonic transfiguration.

Survival is unlikely here. Most of my seemingly mild-mannered fellow “Squashers” live up to their name and splatter hornworms with any available blunt-force implement, more in the spirit of Green Berets than Greenpeace. Others will snatch them into a bucket as chicken-food, which seems brutal, yet fair. The group also defends its use of Bt (bacillus thuringiensis), a naturally occurring bacterial pesticide. There are many types of Bt, and each targets different insect groups at the larval stage, including the caterpillars of Lepidopterae (moths and butterflies).

This microbe treatment seems dicey to me, since my fellow Squashers are shrill advocates for the handsome black, white and yellow-striped caterpillar of the Monarch butterfly (Danaus plexippus). Bt is reportedly safe for Monarchs, in spite of early anti-GM concerns, but some strains are highly toxic to another American butterfly, the Black Swallowtail (Papilio polyxenes). Yet another strain is deadly to honeybees.

Monarch butterfly caterpillar

Luckily for the Monarch caterpillar, humans don’t eat milkweed.


There’s no denying that the hornworm is a glutton. But all caterpillars are. They have to be, devouring many times their body weight in food-plants to take them through various moults (called instars) to metamorphosis. Once inside the chrysalis, the caterpillar melts itself down into a primal ooze, weirdly dissolved by its own enzymes. The genetic goop reorders itself, and a new, winged version of the creature emerges a few days later. The butterfly makes a chrysalis, and the moth a cocoon, but the freaky, slightly horrific process is the same.

“It’s almost impossible for people to encounter the natural world without forming strong opinions about what makes an animal good or bad,” says Dr. Wagner. “It’s Darwinian—something that attacks our food source is obviously going to be hunted down and killed. The trouble there is that the Sphinx moth is a really great pollinator, and we need all of those we can get.”

But folks, let’s keep it real: we’re pleasure-gardeners here. As much as we take pride in our iGram-worthy baskets of gleaming berries and heaps of dewy squashes, our families will not go hungry if our crops fail. Truth be told, this type of gardening is far from cost-effective as food production goes. Start with the cost of water and the cost of real estate in Southern California, and add to it the fact that Posh Squashers and most other garden hobbyists invest in soil amendments, raised garden beds, shade-canopies, equipment like a timed drip system, wire cages and other supports for large plants. Add sweat-equity to the equation, and even at minimum wage, you’ve got yourself one pretty pricey heirloom tomato.

It’s like knitting a sweater. For the price of several skeins of yummy Italian mohair, you can buy two, maybe three machine-made sweaters of excellent quality—and we’re just writing off the skill, patience and time require to knit one, purl two.

In this light, both knitting and food gardening become quaint exercises in nostalgia. We do these things because they make us feel more elemental, more authentic. We trudge back to the Prius after a garden sesh, cheeks stinging with sunburn, boots righteously reeking of steer manure, feeling that we have re-claimed our rightful place on the planet.  Not surprisingly, returning the next morning to find our plants utterly obliterated will often spark the uniquely entitled rage of the apex predator.

California produces 95% of the tomatoes eaten in the U.S., tipping the scales at 2.8 billion pounds in 2020. And they taste like styrofoam, lacking the high-sugar sweetness and tangy acidity of garden-grown. They are grown indoors, thus spared the whims of weather and the constant assault not only by caterpillars but by snails, slugs, rats, mice, possums, squirrels, racoons and all manner of marauding birds that appreciate fresh produce. Commercial crops never know the perfume of rain or the radiance of real sunlight. Bred for uniformity, they’re perfect, and perfectly safe. Just one problem: they don’t taste good.

This is why urban seekers have returned to the soil, sensing that an essential connection has been lost, perhaps forever.  For millennia, farmers literally prayed over their fields, asking for the blessings of saints, offering sacrifices, invoking the deities to ignite life in the sleeping seeds, protect the tenderest shoots from danger, and bring forth an abundant harvest. In this tradition, partnering with the dirt is about sustenance of an unseen kind, as well as literally filling the salad bowl—for Man doth not live by kale alone. But the trouble is, most Squashers arrive with hubris and sod-busting, pest-squishing zeal in place of humility.


“Luckily for Monarchs, human beings have no use for the milkweed plant,” observes Dr. Wagner, milkweed being the food-source of the showy black-and-orange family favorite. “So, they’re easy to love. If Monarch caterpillars liked to eat roses, or lettuce, or strawberries, they’d probably be extinct by now. If Monarchs are the good guys and hornworms are the bad guys, then the Black Swallowtail is right in the middle.”

Black Swallowtail caterpillar

The caterpillar of the Black Swallowtail butterfly munches parsley, dill and fennel, and packs a pungent surprise for predators.

The Black Swallowtail caterpillar, dotted and striped with yellow-orange, lime green, black and white, munches aromatic parsley, fennel and dill, along with parsnip and carrot tops. It’s one of my favorites, because of what’s called an osmeterium. This is an inflatable, retractable balloon of sorts embedded in the caterpillar’s head. When threatened, the caterpillar pops out its osmeterium, which resembles a pair of bright orange horns, or—suggests Dr. Wagner—the forked tongue of a snake, to discourage being snacked on by birds. The sharp aroma accompanying the defensive display is spicy, like the creature’s diet.

I’ve always rooted for the underdog, and while I love nearly all caterpillars, the monarch already has a solid fan-base. And, its vivid colors as both a caterpillar and an adult signal to birds and other predators that it isn’t good to eat. This is an almost universal law of nature: bright yellow, acid-orange, red and blue signal a bitter taste. The Black Swallowtail sends the same visual message with its coloration: steer clear, mockingbird.

The hornworm has no such defenses. If undisturbed, it grows luxuriously large and plump, a gorgeous shade of celadon. Its famous horn is harmless, although some varieties of the worm will thrash and hiss (through spiracles, or air-holes resembling eyes, along the animal’s flanks) when hassled.

But irate gardeners and hungry avians are not the biggest threats to the hornworm’s heroic journey toward flight. Its most formidable adversary is the Braconid wasp (Cotesia congregates), considered a beneficial insect by most gardeners. This parasite injects its eggs into the growing hornworm, and the eggs hatch and turn into wasp larvae that literally eat the host alive from the inside out. A hornworm which appears to be wearing a blanket of bobbing white rice grains is actually in the final excruciating moments of its life: the “rice grains” are the cocoons of the young wasps, which emerge through the caterpillar’s skin and fly off to attack other hornworms and repeat the process.

“That really pisses me off,” says Dr. Wagner. “It’s grotesque and downright ghoulish.” A similar menace threatens the Monarch in the form of the Tachnid fly (Lespesia archippivora). This parasite injects its eggs into its stripey host caterpillar as the worm hangs upside-down in its “J-formation” to begin metamorphosis, or—truly a sacrilege—a bit later in the cycle, into the butterfly’s green, exquisitely golden-edged chrysalis, where the developing maggots mercilessly chow down on the morphing Monarch. “I hate those flies for the same reason,” he adds, with a Zoom shudder. “Nature is all about everything eating everything else, but I admit that the parasites really get under my skin, pun intended.”

Some gardeners care only about their plants, and this is short-sighted.  Healthy gardens require insects (although you can accomplish pollination yourself, with a paintbrush). In addition to their plants, many gardeners also care about Monarch caterpillars, and they fret over the dangers of tropical (versus native) milkweed, and protect the worms in mesh habitats, photographing and journaling though the instars. A few outliers like myself do the same for hornworms.

One non-violent solution to caterpillar control is to plant a trap crop, meaning a crop that is planted adjacent to the garden beds, the idea being to lure any undesirables—in the case of tomato fanciers, the Sphinx Moth—away from your main plantings. To my mind, this is like living in a rough neighborhood and putting iron security bars over just one window. Thieves and moths may be smarter than we think.

Dr. Wagner suggests: “Leave part of your yard or garden wild.  Give up trying to control everything. Surrender to the chaos and mayhem. You’ll be amazed, and kids in particular will enjoy the untamed experience. Doing this brings back a sense of awe, instead of treating your garden like a machine.”

As for tomatoes, farmers markets are full of them, nearly year-round here in Southern California. Every color, every size, every shape. The other day, as I selected a glossy Cherokee Purple for my lunch sandwich (wheat toast, vegenaise, cracked black pepper, sea salt to taste), I noticed a familiar jade-green form clinging to the underside of the still-attached leaf. Still just a baby, about the size of a chapstick.

B-a-a-a-a-h!” barked the vendor, lunging forward to pinch off the offender. “No, no!” I cried out, shielding both tomato and worm with my hat.

The vendor backed off, first puzzled, then amused. “Okay, then. Worm is extra.”

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Some names have been changed to protect their privacy.

Photo of hornworm by

Other photographs by Victoria Thomas


Victoria Thomas
Victoria Thomas is always at the crossroads, like Robert Johnson. She writes about intersections of culture and history and what these crossings mean, in a desire to understand human behavior and help the world awaken to our collective potential for joy. Read her arts writing under the heading “the Sublime”


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