Honey locust moths that emerge in June and after are called the “summer form.” The forewing upperside ranges from rust-colored to orangish to yellow-tan. Usually, there is a postmedian line (running between the midpoint and the wing edge) that bends in toward the hind part of the forewing. This line touches the leading edge of the wing in front of the outer tip. In the cell (a region at the core of the forewing, near the leading edge), there are two small white spots. The hindwing lacks lines but usually has some rosy or reddish shading.
There is a lot of variation in the markings of this species, based on season and individual genetics. In the spring generation, the ground color of the forewing is gray, often with heavier sprinkling of small dark specks. As the season progresses, moths with intermediate coloration occur until June, when the brighter, more colorful summer form predominates.
Larvae, in their mature stage, are green and sprinkled with white specklike tubercles. The second and third thoracic (behind the head) segments have two pairs of reddish horns. There is a reddish taillike horn. There are sharp, pearl-colored spines on the abdominal section (behind the thorax). A white stripe, often bordered by a red stripe, runs down each side. The head is green with yellow bands.
Similar species: The bisected honey locust moth (S. bisecta) is very similar but is usually less abundant. It is generally larger, its postmedian line is straighter and reaches the outer tip of the wing, and the white spots in the forewing cell are absent. It has the same food plants and range as the honey locust moth. At one point they were considered different forms of the same species.