The caterpillar for this moth is a pale green with a sharp-looking horn (looks more like a thorn) at its tail end. This horn has a pale stripe on it as well as thin diagonal pale stripes running along the sides of the body. Small white spots dot the sides. Poplar, cottonwood and willow tree leaves make up the bulk of this caterpillar's diet. Once it has grown in size, the caterpillar pupates in a cocoon made of earth just under the ground's surface. It emerges as an adult moth.