Northern Prairie Wildlife Research Center
Blackish with abundant white flecking. Black dorsal midline flanked by paired red spots on last thoracic and most abdominal segments. Spines, long and shiny black with short side branches. Prolegs red. Caterpillars feed gregariously, writhing and twitching upon disturbance. Food: usually willows or elms but also hackberries and others. Caterpillar: June to September; up to 3 generations in South; 1 or 2 in North.