Picture this: you're walking through a wooded area in the eastern United States, maybe in late summer, and you spot what looks like a small, bright green dragon clinging to a tree branch. It's covered in fierce-looking black-tipped spines, and its head sports four prominent, curved horns. Your first thought might be "run" or "is that thing poisonous?" Let me stop you right there. You've just met the hickory horned devil caterpillar, the larval stage of the stunning regal moth (Citheronia regalis). And despite its nightmare-fuel appearance, it's one of the most harmless and fascinating insects you'll ever encounter. This guide is for anyone who's found one, wants to find one, or is curious about raising them. I've been studying and rearing these giants for years, and I'm here to cut through the myths and give you the real, practical details. You can't mistake it for anything else. A mature hickory horned devil is a beast, reaching up to 6 inches long—about the size of a hot dog. Its body is a vibrant aqua-green or turquoise. The most striking features are the rows of long, black-tipped spines running along its back and sides. The "horns" on its thorax (the segment right behind the head) are orange at the base and black at the tips, and they're surprisingly flexible. They can wave them around if they feel threatened, which is purely for show. Here’s a quick breakdown of key identification features to separate it from other large caterpillars: One thing most online guides get wrong is the color consistency. Early instars (growth stages) are actually a dull brown or orange, and they only develop that iconic green in the final two instars. If you find a small, brown spiky caterpillar on a walnut tree, it might just be a baby devil. The transformation is nothing short of miraculous. The caterpillar stage is the main event—it's when they do all their eating and growing. After that final, massive instar, things get interesting. The caterpillar will stop eating and its color may dull slightly. This is the pre-pupation wandering stage. It will crawl down from its host tree and search for a suitable spot to burrow into the soil. This is a critical moment if you're raising one indoors. They need to burrow. I've seen beginners panic when their caterpillar starts frantically pacing the enclosure, not realizing it's trying to fulfill this deep instinct. Once buried, it forms a tough, dark brown chamber in the soil and pupates inside. It will spend the winter in this pupal stage. Come the following summer, the adult regal moth emerges. And what an adult! It's a large moth with wings patterned in gorgeous shades of orange, gray, and cream. They have no functional mouthparts and live only about a week, just long enough to mate and lay eggs for the next generation. The University of Florida's Entomology Department has a fantastic featured creatures page with detailed images of the entire life cycle. So you've found one and want to observe its metamorphosis. It's a rewarding project, but it's not like keeping a pet in a jar. Here’s my field-tested method, born from a few early failures. Forget the old mayo jar. You need a proper rearing container. A large, clear plastic storage bin (5-10 gallons) with a ventilated lid works perfectly. Line the bottom with a few inches of slightly moist (not wet) peat moss or coconut coir. This will be crucial for pupation later. Add some sticks for climbing. The goal is to mimic the forest floor. Hickory horned devils are named for a reason, but their diet is broader than just hickory. They are specialists on trees in the walnut family (Juglandaceae). Here’s the hierarchy of preferred host plants, from most to least favored: The biggest mistake? Assuming "any green leaf" will do. Offering sycamore or oak will result in a caterpillar that refuses to eat and slowly starves. You must provide fresh cuttings from an acceptable tree. Rinse the leaves lightly to remove pesticides or bird droppings. Change the cuttings every day or two, inserting the stems into a small water pick (covered with foil or cotton so the caterpillar doesn't fall in and drown). Keep the container clean. Remove frass (caterpillar poop) daily—it's surprisingly large and plentiful. Maintain slight humidity by occasionally misting the side of the container, not directly on the caterpillar or the soil. When your caterpillar stops eating, turns a duller green, and starts wandering, it's time. This is where my first attempt failed. I didn't have enough soil. Ensure the substrate layer is at least 4-5 inches deep, packed loosely enough for it to burrow. It will disappear. Do not dig it up. Mark the container with the date and move it to a sheltered, unheated space like a garage or shed for the winter. It needs to experience the cold dormancy. In late spring or early summer, you might hear scratching from the container. The moth is emerging from its pupal case underground. It will crawl to the surface and need sticks to climb on to hang and inflate its wings. This process takes a few hours. Once its wings are dry and full, you have a stunning regal moth. The ethical choice is to release it near suitable habitat (woodlands with host trees) at dusk so it can find a mate. Finding and raising a hickory horned devil is a unique way to connect with a dramatic part of local ecology. It transforms something that looks frightening into a creature of delicate beauty and fascinating instinct. It teaches patience and respect for natural processes. Just remember to give it what it truly needs—the right leaves, the deep soil, and ultimately, its freedom.
What’s Inside This Guide
What Does a Hickory Horned Devil Caterpillar Look Like?
Feature
Hickory Horned Devil
Similar Caterpillars (e.g., Tomato Hornworm)
Color
Bright aqua-green
Usually darker green with white markings
Spines/Horns
Multiple rows of long, black-tipped spines; four prominent head horns
A single, stiff "horn" on the rear end
Size at Maturity
5 to 6 inches
3 to 4 inches
Head Color
Orange or reddish-brown
Usually same as body color
The Life Cycle: From Devil to Regal Moth
How to Care for a Hickory Horned Devil Caterpillar (Step-by-Step)
Step 1: The Right Setup
Step 2: The Food Source (This is Non-Negotiable)
Step 3: Daily Maintenance and The Big Burrow
Step 4: The Emergence
Your Top Hickory Horned Devil Questions Answered
Before You Start: Always check your local regulations about collecting insects. In most places, collecting a few for personal observation is fine, but it's good practice to know the rules. Source your caterpillars ethically—finding them in the wild is best. Avoid suppliers that might deplete local populations.
A Critical Safety Note: Are hickory horned devils poisonous? No. Their spines look menacing but are completely harmless and not venomous. You can safely handle them, but be gentle. Support their whole body. The real risk is to the caterpillar from our oils and germs, so limit handling.
I found a hickory horned devil on the ground. What should I do?
If it's actively crawling on soil or pavement, it's almost certainly in its pre-pupation wandering phase. It's looking for a place to burrow. The best thing you can do is move it to a safe, wooded area with soft soil, away from foot traffic and predators. Don't put it back in a tree—its instinct now is to go down, not up.
How common are they? I've never seen one.
They're not rare, but they're masters of camouflage and spend most of their time high in the canopy. You're most likely to spot one in late summer (August-September) or find one after it has come down to pupate. Checking the leaves of sweetgum trees for large, ragged chew marks is a good way to start your search.
Can I keep a hickory horned devil as a pet long-term?
Not really. The caterpillar stage lasts a few weeks, the pupal stage months, and the adult moth only lives about a week without feeding. The cycle is the main attraction. The goal of keeping one should be observation and successful release, not permanent captivity. It's a temporary, educational project.
What are the main reasons raising them fails?
From my own blunders and talking to others: 1) Wrong food (this is #1 by a mile). 2) Container too small or without proper burrowing substrate. 3) Disturbing the pupa during winter. 4) Letting the food leaves dry out or become moldy. 5) Trying to keep the adult moth alive—it's not meant to be.
How can I tell if it's a boy or a girl?
You can't easily tell from the caterpillar. As pupae, females are generally larger and heavier. As adult moths, females have thinner, more pointed antennae, while males have large, feathery antennae they use to detect female pheromones. The male's antennae are a stunning piece of natural engineering.
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