Northern Prairie Wildlife Research Center
Purple or brown gray marked with black, pale gray, and tan. Head flattened and sloping, somewhat lobed above; spots coalescing to form brown patch over lobes. Second and third thoracic segments swollen. Legs short and appressed to body. Setal bases often blackened. Dorsum enlarged on fifth abdominal segment, lower front half of swelling with indistinct transverse band. Other Plagodis occur in eastern United States with similar caterpillars. Food: deciduous and coniferous trees. Caterpillar: May to November; 2 generations in North.