Northern Prairie Wildlife Research Center
Outline unique with backward projecting, fleshy humps on second and third abdominal segments; raised angulate eighth abdominal segment. Head with front flattened, slightly lobed to either side, festooned with black spots, and pale line running from antenna to vertex. Oblique lines to either side of midline on midabdominal segments. Caterpillar of N. simplaria tend to be lighter in color, often tinted with purple-gray, and mottling on eighth segment more red-orange. Food: poplars and willows. Caterpillar: July to September; 1 generation with partial second.