Five years ago, I discovered at Center, in the trunks of poplar trees (Populus tremuloides) several pupal cases of a Cossus, which, by their differing from the other cases known to me, of C. Robiniæ and C. querciperda, I had reason to believe was an undescribed species. This year, on the 14th of June, on examining some infested trees, several pupal cases were discovered projecting half-way from the trunks, and an imago, which had apparently just emerged, and was resting on the stump of a broken limb. The colors of the moth so exactly simulated the surface on which it rested that it was with difficulty observed, even when looking directly at it.