Armyworm, common name for the caterpillars of any of several American species of moths that travel in groups from one area of vegetation to another. In one species the adult moth has a single white spot on each front wing, which is otherwise uniformly a dull brown color, and has a wingspread of about 4 cm (about 1.5 in). The caterpillar, which is almost 5 cm (almost 2 in) long when fully grown, is green, with three yellowish stripes down the back and a darker stripe on each side. The caterpillars feed chiefly on grasses and are usually most troublesome in cornfields. They feed only at night; by day they hide in the sod or among the inner leaves. When the caterpillars have completely stripped an area, the group moves to another plot. They are periodically abundant in most parts of the United States east of the Rocky Mountains. In the southern United States six generations may occur in a season.
Scientific classification: Armyworms belong to the family Noctuidae of the order Lepidoptera, class Insecta, phylum Arthropoda. The name is applied particularly to the species Pseudaletia unipuncta.