The army cutworm is the immature form of ''Euxoa auxiliaris''. Together with other moths that are locally abundant and that have scales that dislodge from the wings, the adult moth is called a miller moth. These native North American larvae consume emerging small grains, alfalfa, and canola in the southern Great Plains and southern Canada. Larvae feed above ground at night and usually hide in soil during daylight, but will also feed on cloudy days. On dry, low elevation rangelands of the U.S. Intermountain West, army cutworms consume exotic cheatgrass (''Bromus tectorum'') and mustards to produce cheatgrass "die-offs." Within these bare areas, the larvae also defoliate native shrubs including four-wing saltbush (''Atriplex canescens'') and

sagebrush Sagebrush is the common name of several woody and herbaceous species of plants in the genus ''Artemisia (plant), Artemisia''. The best-known sagebrush is the shrub ''Artemisia tridentata''. Sagebrush is native to the western half of North Amer ...

(''Artemisia'' spp.). The miller moth is a seasonal nuisance in the spring in states including

Montana Montana ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States. It is bordered by Idaho to the west, North Dakota to the east, South Dakota to the southeast, Wyoming to the south, an ...

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...

Colorado Colorado is a U.S. state, state in the Western United States. It is one of the Mountain states, sharing the Four Corners region with Arizona, New Mexico, and Utah. It is also bordered by Wyoming to the north, Nebraska to the northeast, Kansas ...

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New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

, and

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, as they hatch in the low-lying farmlands, then migrate to higher elevations for the summer. They return as the weather cools but in smaller numbers. They are considered nearly impossible to control through normal pest extermination techniques because a new batch shows up every day as they migrate. With their very small bodies, they enter homes (attracted by the light) in the evening through any available crack or crevice (doorjamb, chimney, etc.) and residents in migration paths report dozens of moths per day entering their homes and garages. However, other than being a nuisance, they are not considered harmful.

Location

''Euxoa auxiliaris'' is commonly found in the Western section and prairies of the United States. They are known to travel to

alpine climate Alpine climate is the typical climate for elevations above the tree line, where trees fail to grow due to cold. This climate is also referred to as a mountain climate or highland climate. Definition There are multiple definitions of alpine cli ...

regions in late June and early July where they feed at night on the nectar of wildflowers. Army cutworms are one of the richest foods for predators, such as

brown bear The brown bear (''Ursus arctos'') is a large bear native to Eurasia and North America. Of the land carnivorans, it is rivaled in size only by its closest relative, the polar bear, which is much less variable in size and slightly bigger on av ...

s, in this ecosystem, where up to 72% of the moth's body weight is fat, thus making it more calorie-rich than elk or deer. This is the highest known body fat percentage of any animal.

References

Euxoa Agricultural pest insects Moths of North America Moths described in 1873 Taxa named by Augustus Radcliffe Grote {{agri-stub