Distribution
Io moths are common throughout eastern North America, north to southern Canada. They range west to southern Arizona and south to Central America, at least as far as Costa Rica. Over 200 species of Automeris and related genera in Hemileucinae occur south of the U.S. border (Collins and Weast 1961).
Identification
The io moth adult is 2.0 to 3.5 inches (50 to 87 mm) in wingspan and easily recognized by the large eye-spots of the hindwings. Adult males are mostly yellow, while females have brown forewings. Subspecies A. io lilith (Strecker) of Florida has male adults with distinctly red-brown forewings, especially in south Florida; the same type of red form is also found in southern Mexico and the Bahamas. The larvae have characteristic long yellow or green spines covering most of the body. Only a few other caterpillars may look similar, but these do not have the well-defined red and white lateral line. The io moth caterpillar has at least three discrete color forms: the usual last instar form is light green, with a distinct lateral body strip of red and white. Earlier instars are yellow overall and the lateral line is reduced. There also is a blue-green color form of last instars (Collins and Weast 1961).
adult
caterpillar, early instar larvae
caterpillar, last instar larva
Biology
Io moth larvae are leaf feeders, gregarious in early instars, then solitary as they grow. After several weeks of feeding, they make a simple paper-like cocoon away from the host plant. In Florida, there are three to four generations per year. There usually is only one generation in northern states.
Host Plants
The io moth has a long list of host plants, with over 100 recorded plant genera in North America, including such diverse plants as roses, cotton, hibiscus, azaleas, willows, clover, and palms. In Florida, io moth larvae are commonly found on oaks and other hardwoods.
Management
If present in large numbers, caterpillars can be sprayed with a bacterial spray (Bacillus thuringiensis) or any common insecticide although usually the larvae are not so common as to warrant spraying. Larvae should not be touched. Remedies for relief of urticating pain include initial removal of any remaining inserted spines by the use of adhesive tape, followed by ice compacts, mentholated vaseline, or an antihistamine medicine (Riley and Johannsen 1938, Frazier and Brown 1980).
