These caterpillars are protected by venomous spines, and can deliver a sting comparable to a honey bee (although most stings are more like a stinging nettle – you’ll feel it, but you’ll be okay!). They eat various trees and plants including hackberry, mesquite, currant, blackberry, pear, maple, alder, poplar, willow, and wisteria. The Io caterpillar grows up to be a very beautiful moth, with huge eyespot markings on the hind wings that it flashes to scare away birds and other predators. If you find one of these caterpillars, consider yourself lucky, but don't pick it up with bare hands!