The entire body of the io moth caterpillar is covered with clusters of pale green, black-tipped, branched spines that are very irritating when they come in contact with the skin. These whorls of spines arise from small tubercles. Full-grown larvae are about 2 to 3 inches long. The body is pale green except for white and reddish brown stripes running the length of the abdomen and associated with the spiracles. The young caterpillars are usually gregarious, but as they grow they become solitary. Common host plants include maple, sassafras, oak, hickory, elm, apple, beech, cherry, black locust, mulberry, dogwood, sycamore, and even corn and other grasses.

About the family

Royal moths and silkworm moths of the Saturniidae family include many of the largest and most colorful moths in North America and the world. These large caterpillar species are usually not considered pests. Although a single individual can consume relatively large amounts of foliage, their numbers rarely reach levels that would warrant control. But there are a few species that can do significant damage to many forest tree species. Upon completing their larval development, most saturniid caterpillars will pupate in large, tough silken cocoons usually attached to twigs or leaves or found on the ground. Many species have only one generation per year.

IPM1019, new February 2003