Mr. Edwards describes and figures a female of this large species, from Michigan, in Proc. Ent. Soc., Phil. 1863. The following is a description of the male, collected by me in Iowa, July 4. The spots are numbered as in Mr. Edwards account:

The secondaries, above and beneath, are like those of the female.—Above. from the border of the primaries to near the base, the color is yellow, except the sexual dash and dark veining; an oblique line at end of the cell, from which a dark shade extends to the outermost spot; resting midway on this, a narrow shade runs from the first three spots along the subcostal vein.

It is not, I believe, generally known that, closely as these two insects resemble each other in the larval and pupal states, they may, nevertheless, be readily and invariably distinguished by the constant differences in the anterior horns of the former and in the hump of the latter. I was fortunate enough, the present summer, to have several larvæ of each species feeding, as also several pupæ of each hanging, at one and the same time ; and with the exception of the characters here given, I do not think there are any other distinguishing features to be relied upon.