The stiff hairs, or spines, are mildly poisonous, with the sting somewhat less painful than other stinging caterpillars. Some individuals report severe irritation nevertheless. Io Moth Adult moths appear at lights from late-May through July. Larvae feed on corn foliage, cotton, roses and a wide variety of trees and shrubs. There is believed to be only one generation in most years with overwintering passed as a pupa inside a tough oval cocoon, often enclosed in leaves on the ground.
Moths emerge in the spring and summer, mate and lay eggs.
The sting mechanism is similar to the puss caterpillar, but usually less severe. Hosts include hackberry, oak, maple, sycamore, elm, English ivy, rose and other plants. Stings can be quite painful. There is an intense local burning at the contact site, soon radiating a considerable distance as localized swelling occurs. The inflammation can spread several inches around the sting and, in sensitive persons, lymph nodes under arms and in the groin may enlarge.