In late summer, there’s a fluffball thing on the leaf next to me, moving around. Looks like a bit of lint, right? You’d reach down and pick it up. But don’t. Before you touch it, know this: not all fuzzy caterpillars is safe for handling. Some are so defended they’ll make you wish you hadn’t.
What are these hairs, exactly? Different types of hair present different dangers. Biology separate fuzz into clear categories. Soft setae are the type of hair on most caterpillar that you can touch with no consequence. They serves as camouflage or sensory organs. Urticating hairs, found on other species, are barbed, hollow fibers like mini-harpoons that detatch and lodge in your flesh. They prompt a histamine reaction: an itch-inducing rash lasting days. And then there are the venomous spines found on some species (such as the Buck Moth or Puss Caterpillar) that inject true toxins. The result? It causes an immediate, painful sting followed by nausea. It’s not just irritating; it’s also a chemical attack.
Why You Should Not Touch Fuzzy Caterpillars
You don’t need guts; you just need some knowledge of what each of these category might be. Look for color patterns first: The Woolly Bear (safe) typically has orange and black bands on its body. The Yellow Woolly Bear (irritating) will tend to be solid pale yellow. And if you spot anything that resembles a silky golden toupee without any apparent structure (get outta Dodge right now). Chances are it’s the Puss Caterpillar, the most venomous larval critter in all of North America. Evolution wants your predator brain to believe it’s a softie so it looks inviting. It is a trick.
A big tip-off is host plants. Many species of caterpillars is very particular about where they grow up; seeing one on certain trees greatly limits the suspects. For instance, that spiny caterpillar you find under an oak leaf in early spring are likely the Buck Moth. The Hickory Tussock is typically found on hickory trees, as are its stinging hairs. The sycamore tree attracts its namesake tussock moth and so on. Familiarity with your local flora means anticipating who may be crawling around on it…before getting too near to examine it closely.
Understanding their life cycle helps explain their odd appearance. What’s all that hair for? It is used for camouflage; many species weaves cocoons out of discarded hair. It also serves other functions, such as protection from predators. And then there are many species that molt several times as the larva grows to eventually become pupae. They consume food and grow over a period of several months. They don’t get all those spines or hair until after they’ve reached adult size, which is why you’re more apt to see adults later in the year when they’ve had a chance to mature… and arm up with their collection of armor.
The safety rules are easy but inflexible: Don’t pick up any caterpillar (or at least until you’re sure what it is). And even when you are, always wash your hands! Some will release defensive chemicals as well as their hairs so why take a chance? Wash off embedded hairs with soap and water; sticky tape will help remove them if they cause irritation or a sting. Apply ice to reduce swelling. If symptoms like severe reactions outside the contact site or difficulty breathing occur, go see a doctor.
That’s where a smartphone camera app or a hand lens comes in: Snap a picture from a safe distance, then ID it on-line. Surprisingly, apps such as iNaturalist does a good job telling the difference between an innocuous woolly bear and a toxic imposter. That will satisfy your curiosity without getting you into trouble (and perhaps saving you some discomfort).
There is no need to fear fuzzy caterpillars. We should of simply admire their defense mechanisms and realize that they are important parts of the ecosystem. They provide food for birds and other wildlife and add to the overall biodiversity here. Eyes wide open, fingers tightly shut, let’s learn about the id of these wonderful creatures from a safe distance. Enjoy them…but don’t pay the price with your own skin. If it seems too good to be true, it probably stings.