Some caterpillars may look cute and fuzzy, but don’t be fooled—many carry painful surprises in their spines and bristles. These tiny critters, often decked out in bright colors and intricate patterns, can deliver stings that range from mildly irritating to seriously painful or even deadly. Here are ten caterpillars you’ll want to admire from a safe distance.
1. Puss Caterpillar
The puss caterpillar might look like a furry friend, but it’s really a venomous foe. This caterpillar, considered among the most toxic in the world, can leave you with pain worse than a bee sting, radiating into your bones. As if that wasn’t enough, puss caterpillars have also been known to fling their droppings as a form of defense. They’re common along the East Coast, so if you spot a fluffy tan caterpillar lounging on a tree, keep your distance to avoid the agony it can deliver.
2. Hickory Tussock Caterpillar
The hickory tussock caterpillar sports a striking black-and-white appearance that almost resembles a tiny skunk. Much like skunks, they’re best avoided. This caterpillar’s hairs contain toxins that can trigger severe allergic reactions, especially in children and those with sensitive skin. Contact can result in swelling, itching, and redness, and some unlucky victims experience even more intense reactions. Found in the northern areas of the U.S., it’s safest to steer clear of these guys.
3. Saddleback Caterpillar
The saddleback caterpillar’s bold green “saddle” marking might grab your attention, but this colorful warning is a serious one. The bug’s venomous spines can inject toxins that rupture blood cells, potentially causing a series of unpleasant symptoms: migraines, stomach pain, and blood-related issues. In severe cases, people have experienced anaphylactic shock and hemorrhaging. These caterpillars inhabit the eastern U.S., where they munch on leaves and defend their territory. If you spot one, it’s best to let it be and avoid a painful run-in.
4. Buck Moth Caterpillar
Covered in menacing spines, the buck moth caterpillar is not a critter you want to accidentally brush against on a hike. This caterpillar’s spines can inject venom that causes intense pain and, in the worst cases, can lead to breathing difficulties. Some people have even experienced anaphylactic reactions—which can be life-threatening without quick intervention. Found in wooded areas, the buck moth caterpillar’s sting is more than enough of a reason to keep an eye on where you step.
5. Bag Shelter Caterpillar
Native to Australia, the bag shelter caterpillar is notorious for causing miscarriages in horses due to its venom. Its spines contain an anticoagulant that can lead to internal bleeding, which is particularly dangerous for pregnant horses. Humans can also experience skin irritation and allergic reactions from contact. If you’re around the Australian pine trees where these caterpillars make their homes, it’s a good idea to keep pets and livestock far away.
6. Monarch Caterpillar
Famous for its striking stripes, the monarch caterpillar is a beautiful creature, though highly toxic. Feeding exclusively on milkweed, a poisonous plant, the caterpillar absorbs toxins called glycosides that remain in its body into adulthood. While monarch caterpillars don’t actively sting, they can still cause toxic reactions if handled or ingested. This defense keeps predators away, but it’s wise for people to keep a respectful distance from this venom-loaded icon, too.
7. Pine Processionary Caterpillar
The pine processionary caterpillar is a serious danger to curious pets and unwary humans alike. Its venomous hairs can cause painful skin rashes in humans, and if a dog so much as licks one, it can result in necrosis—a form of tissue death. Found across Europe and spreading to other regions, they often form long lines, or “processions,” on pine trees, creating a fascinating sight despite the danger. If you find yourself in their territory, keep a close eye on children and pets.
8. Io Moth Caterpillar
A bright green creature with intimidating spines, the Io moth caterpillar packs a sting that can cause swelling, pain, and a nasty rash. Scientists are studying this caterpillar’s venom for potential medical applications, particularly for anti-inflammatory drugs. But while they may hold scientific promise, Io moth caterpillars are still best admired from afar, especially since their spines can break off under your skin and lead to lasting irritation.
9. Stinging Rose Caterpillar
Draped in vivid colors, the stinging rose caterpillar is a striking sight, but those eye-catching spines are as dangerous as they are beautiful. Each venomous spine injects toxins that can lead to swelling, rashes, and intense itching. Often found on garden plants, this caterpillar can be a painful surprise for those tending to their outdoor spaces. Gardeners especially should watch for this colorful critter to avoid any uncomfortable encounters.
10. Hag Moth Caterpillar
The hag moth caterpillar, or “monkey slug,” looks like it comes straight out of a sci-fi movie. Its strange body shape and furry appearance make it a true standout, but those “hairs” are actually venomous spines. A sting from this outlandish creature is comparable to a bee sting and results in pain, itching, and swelling. Although not deadly, the discomfort it causes can last longer than expected, making it yet another untouchable fascination.
