Caterpillar is the common name for the larvae of members of the order Lepidoptera (the insect order comprising butterflies and moths). Caterpillars, or larvae hatch from the eggs in the early spring about the time that the leaves on their host plants emerge. Some caterpillars can defoliate trees and shrubs, can cause damage to electrical lines and other problems depending on the abundance of them. There are some that help with plant pollination and there are others that can sting.
There are four major stinging caterpillars occurring in U.S.which are the puss caterpillar, saddleback caterpillar, Io moth caterpillar and hag caterpillar.These caterpillars do not possess stingers, but have spines (nettling hairs) that are connected to poison glands. Some people experience severe reactions to the poison released by the spines and require medical attention. Others experience only an itching or burning sensation.