Northern Prairie Wildlife Research Center
Superb twig mimic; green, brown, or gray dappled with minute white spotting; pronounced leaf-scarlike swellings. Head flattened and directed forward with long antennae. Legs of third thoracic segment greatly swollen at their base, commonly held out from body. Dorsum of second and fifth abdominal segments, and venter of third with raised transverse ridges. Eighth abdominal segment with low, darkly pigmented dorsal warts. Food: prefers oaks, hickories, elms, ashes, and maples, but caterpillars defoliate many hardwoods during outbreaks. Caterpillar: May to August; 1 generation.