Adult moths, also known as millers, emerge from these cells in May and early June. An interesting phenomenon with this cutworm species is its seasonal migration to high elevations in the Rocky Mountains. Adult moths are active at night at these higher elevations, feeding on alpine flower nectar. During the day they form dense aggregations under stumps, logs and other structures that offer them protection from direct sunlight. Wildlife researchers report that these dense aggregations of cutworm moths are an important food source for grizzly bears in the absence of high-quality forage alternatives in July and August.
Adult moths return to the plains in late summer and begin laying eggs.
Dry periods during August-October are detrimental to egg hatch and larval survival of army cutworms. Army cutworms have one generation per year. The forewing of the adult has a prominent circular spot and kidney-shaped marking. The hindwing is grayish-brown with a whitish fringe. A narrow, pale mid-dorsal stripe is usually present.