Dull green to brown with a large dark spot above each abdominal proleg. Resident armyworms are further supplemented by migrants that arrive during the first week of April. There are either two to three generations each year in Missouri, but the larvae of the first generation in May and June causes the most feeding damage.
Female moths prefer to lay their eggs in dense, grassy vegetation.
In some years the true armyworm will only feed on plant foliage, whereas in other years it also may cut the awns and seedheads. True armyworms are most destructive to wheat and other small grain crops when wet weather causes lush growth and lodging in the fields. The true and fall are the primary armyworm pests on corn. True armyworms begin feeding on the lower leaves before progressing to the top of the plant. Damage appears as irregular notching at the leaf margins.