Alpine-aggregation
Guides
Euxoa
miller moths, cutworm moths
Euxoa is a genus of noctuid moths established by Jacob Hübner in 1821, comprising approximately 305 species distributed primarily across dry and semi-dry regions of the northern hemisphere. The genus is notably absent from South-East Asia and Australia. Larvae are cutworms that feed on surface vegetation and occasionally climb plants. The genus includes the army cutworm moth (Euxoa auxiliaris), a significant agricultural pest whose adult aggregations serve as a critical food source for grizzly bears in the Greater Yellowstone Ecosystem.
Euxoa auxiliaris
Army Cutworm Moth, Miller Moth
Euxoa auxiliaris, the army cutworm moth, is a seasonal migrant and agricultural pest in the Great Plains of North America. The larval stage damages field crops by cutting stems and feeding on foliage, while adults undertake remarkable long-distance migrations to alpine talus slopes in the Rocky Mountains to escape summer heat. These aggregations serve as a critical, high-calorie food source for grizzly bears during their pre-hibernation hyperphagia. Adults are commonly called 'miller moths' due to the fine, easily-shed wing scales that resemble flour dust.