D: Yaël, caterpillars are a gardener’s enemy. I can’t keep the armyworms out of my beans, and a pack of hornworms is eating up my tomatoes. And what about their hair? It’s enough to give me hives.
Y: That’s about the worst they can do, Don, to you at least. Most caterpillars are covered in hair-like bristles called setae (SEE-tee). These tiny filaments are often too pale to see. But a number of caterpillars are covered in thick swathes of setae that they mean for us to see and to heed.
D: The caterpillars in my garden are covered in setae that can cause some mild skin irritation for people with sensitive skin. Setae act like caterpillar adhesives that have detachable ends that can lodge in the skin of an unlucky handler. The small ends can also float into mucus membranes, like in our eyes, and prove almost impossible to extract.
Y: Color camouflage and setae allow the hornworms in your garden to blend in seamlessly with tomato stalks. Other disguised caterpillars are truly dangerous, with hollow bristles connected to venom sacs. A few stinging caterpillars live in the U.S.
D: One of those is covered in a dense wooly coat that makes it resemble a Persian cat, garnering it the name the puss caterpillar. Beneath the puss caterpillar’s wooly fur are many short venomous spines; for an unsuspecting trespasser these spines deliver a sting, causing radiating pain that’s often more severe than other caterpillar stings.Y: Adventurers of the wild, be aware but not anxious. Most hairy caterpillars are harmless and beautiful to behold, intent only to eat their way to metamorphosis—right through Don’s garden, apparently.