The locations of their attacks vary each year throughout the state. They are most severe in the fall of the year when they defoliate plants rapidly in usually unpredictable sites. Armyworm is correctly used to mean only the one species, P. unipuncta. Larvae, or caterpillars, are green or brown with various markings. Color depends on the species, individual variation and food.
Larval development occurs by molting the outer skin.
The pupa, or resting stage, does not resemble a caterpillar, but is brown and hard-shelled. It is found in the soil where it lies almost motionless. Adult armyworms are moths that often can be found in abundance around outside lights. They vary in coloration and markings depending on the species involved. Eggs are very small, are seldom seen and are laid at the base of appropriate host plants.