The hemlock moth (Agonopterix alstroemeriana), also known as the defoliating hemlock moth or poison hemlock moth, is a moth species of the family Depressariidae. Of Palaearctic origin, it was first found in North America in 1973 when it was accidentally introduced. It has been used in biological control of the lethally toxic poison hemlock (Conium maculatum), which is eaten by its caterpillars (larvae). The larval form grows to about 12 mm, while the adults wingspan is between 17 mm and 19 mm.