Northern Prairie Wildlife Research Center
Green (in low-density populations) to black (especially high-density populations). Many forms with pale subdorsal, supraspiracular, and subspiracular stripes. Dorsum often darkly colored. Abdominal segments frequently with black spot behind spiracle. Distinguished from other loopers by presence of rudimentary prolegs on fifth abdominal segment. Occasionally a pest. Food: new foliage of many hardwood species. Caterpillar: May and June; 1 generation.