Larvae are dark gray to black, robust, and 1 to 1½ inches long. Many small protrusions or tubercles give these worms their characteristic “greasy” appearance. The head capsule is brownish, and larvae go through five to nine instars, depending on environmental conditions, before pupating. Adult black cutworms are relatively large, heavy-bodied moths with 1- to 2-inch wingspans. They are a nondescript grayish-brown color. Forewings may have a mottled appearance. Hind wings are off-white with tan borders. Like most adult cutworms, the black cutworm moth can crawl rapidly to seek shelter when exposed.
The larger larvae descend the host plant at dawn and remain in the soil during the day, feeding primarily at night or during cloudy days. Mature larvae pupate in the soil and adults emerge later to start the cycle again.