Morphological variation in populations of eastern North American buckmoths was examined. Samples of 25 males each were analyzed from four points along a north-south line approximately 800 km long from Schoolcraft Co., Michigan to Vinton Co., Ohio. Clinal variation was demonstrated from higher to lower latitutdes: (1) forewing length from smaller to larger; (2) forewing white band width from wider to narrower; and (3) darkness of the black background of the wing from lighter to darker. No logical way was found to separate these four populations into subspecies or species based on morphological characters.