Most caterpillars have long hair called setae covering their bodies. This hair act as a defense mechanism. The hairs often have detachable tips that will irritate would-be predators by lodging in the skin or mucous membranes.
Here are a trio to avoid: the puss caterpillar, the hickory tussock caterpillar and the io moth caterpillar.
The most venomous caterpillar in the United States, the puss caterpillar, got its name because it resembles a cuddly house cat. Small, extremely toxic spines stick in your skin releasing venom. At first the sting feels like a bee sting, only worse. The pain rapidly gets worse and can even make your bones hurt. People who have been stung on the hand say the pain can radiate up to their shoulder and last for up to 12 hours.
One dapper critter called the hickory tussock caterpillar has a velvety back and sweeping bristles. It looks more like a vintage feather boa than a caterpillar and is widely distributed in the eastern half of North America.
Some people have little to no reaction to the hickory tussock’s sting, but others have a reaction that ranges from a mild to severe rash comparable to poison ivy. It’s microscopic barbs may cause serious medial complications if they are transferred from the hands to the eyes. The adult moth flies away in May and June.
Caterpillars have to eat a lot. Within a few weeks of devouring as much greenery as physically possible, an io caterpillar can go from being a half-inch-long worm to a nearly three-inch-long monstrosity, brilliant green with red and white racing stripes like the Io mother caterpillar:
Io caterpillars are indeed capable, and more than willing, to deliver a painful sting. If you brush up against these spines, the tips will break off and start to inject venom.
So what do you do if you get stung by any of these toxic caterpillars? Place Scotch tape over the affected area and strip off repeatedly to remove spines. Apply ice packs to reduce the stinging sensation, and follow with a paste of baking soda and water. If you have a history of hay fever, asthma or allergy, or if allergic reactions develop, contact a physician immediately.