Caterpillars are black with eight orange-yellow stripes, are and about 2 inches long when fully grown. The second segment behind the head has two long, curved "horns".
Trees in forests, parks and cities can be defoliated. Red and white oaks are potential hosts, but in Maryland, species in the red oak group seem to be favored.
Adults lay eggs on the undersides of leaves from June to July. Caterpillars feed for 5 to 6 weeks in July to September. After feeding is complete, mature larvae pupate in the soil where they overwinter. There is one generation per year.
Severe outbreaks rarely last more than two years due to natural enemies. Control is usually not warranted, except to control caterpillar nuisance and to protect weakened or high value trees.