IO Moth
Automeris io (F.) (Saturniidae)

L.L. Hyche, Associate Professor
Department of Entomology & Plant Pathology
Auburn University

Range of the Io moth includes much of the eastern half of the United States. The caterpillar (Photo 1) feeds on foliage of a wide variety of plants, including clover, grasses, various herbaceous and crop plants, shrubs, and some hardwood trees. Some trees listed as hosts are apple, black locust, cherry, hackberry, hickory, maple, and oak.

Life Cycle, Description, and Habits

The Io moth overwinters as a pupa in a thin, brown cocoon in debris and litter on the ground. Adults emerge in spring, generally along in May. Moths (Photo 2) are fairly large, wingspread is 50 to 80 mm. Coloration varies from yellow to tan, reddish brown, to purplish red. Each hind wing has a large, dark, circular eyespot. These spots, to a potential predator, may appear to be eyes of some animal and, thereby, serve to defend the moth against predation.

Females lay eggs in clusters. Larvae are present during June-October. The number of generations per year varies within the range. Two generations probably occur in Alabama. The full-grown caterpillar (Photo 1) is 60-65 mm long. Head and body are yellowish green. There is a broad white line along each side, bordered above and below by thin red lines. Prolegs and thoracic legs are red. Raised tubercles bearing whorls of branched spines occur on each segment along the back of the body. Spines are poisonous and can cause severe nettling when brought in contact with skin.

Occurrence, Damage, Importance

Through the years, the Io moth has been scarce in Alabama. While trees are listed as hosts, the caterpillars are actually rarely found on foliage of trees. The Io moth caterpillar is best known for its poisonous spines and its ability to "sting."

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All photos courtesy of  Lacy L. Hyche