Army cutworm

The adult army cutworm moth has a wing span of about 1 1/2 inches and is typical of the "miller moths" that are commonly observed. The moth has five color forms, ranging from a lighter form with fairly distinct wing markings to a darker melanic form with less distinct wing markings. Female army cutworm moths lay their eggs directly onto soil. They seem to be attracted to bare areas such as overgrazed pastures, alfalfa stubble, stressed grassy areas, and newly planted or tilled cropland. Females lay from 1,000 to 3,000 eggs from late August until late October. The result of this extended ovipositional period is a great variation in larval size within fields.
The eggs hatch shortly after they have been exposed to moisture (i.e. rainfall). Larvae continue to feed as long as temperatures are favorable, and partially grown larvae overwinter in the soil. Larval feeding activity resumes in late winter or early spring when soil temperatures increase. Army cutworms become active at relatively cool temperatures, possibly even below 40 F, because solar heating warms soil temperatures well above the air temperature. Feeding continues through the spring. Fully grown larvae burrow into the soil, create an earthen chamber, and pupate. Adults emerge from the soil in May and early June to complete the life cycle. Generally, larvae of the army cutworm have a pale grayish body color that is splotched with variable white or light markings. The upper surface is lighter with a pale stripe along the center of the back. There is a lighter band along the side of the larvae below the spiracles. Larvae can attain lengths of 1 1/2 to 2 inches when fully grown.
The most prominent trait of the army cutworm moth is its migration pattern. Adults emerge in May and early June and feed on a variety of nectar-bearing flowering plants. These moths gradually migrate westward toward the mountains and continue to feed on available nectar sources as they ascend in elevation. As they move westward, they rest during the day in dense vegetation or seek shelter in garages, attics and living areas of houses, and can become a significant nuisance pest at this time. During outbreak years, tremendous numbers of these moths can congregate around buildings and residential areas. Moths may remain in these areas for several days, feeding on local nectar sources. However, when temperatures begin to warm consistently and flowering of major plants in the area has ceased, the moths will move westward to higher elevations offering cooler temperatures and new sources of food. The moths spend the summer in the Rocky Mountains, and in late August and September they return to the plains to mate and deposit eggs.