A migration of adult army cutworms, Euxoa auxiliaris (Grote) (Lepidoptera: Noctuidae) at high elevation

A large migration of adult Army Cutworms, Euxoa auxiliaris (Grote) crossed the Beartooth Plateau above treeline (3000-3360 m elevation) on the Montana-Wyoming border during 2-8 July 1989. Thousands of moths were in flight throughout the daylight hours, and many paused to nectar from willow (Salix nivalis and S. glauca) flowers. Density of moths on S. nivalis mats was about 30 m(-2) on 6 July, during peak abundance. Migratory movement corresponded to a temporary warming period in the alpine. Flocks of up to 75 Common Ravens (Corvus corax) appeared during the migration to feed on moths, and some remained in the alpine two weeks after the moth migration had passed. No diurnal migration of moths occurred on the Beartooth Plateau during July 1983, 1984, 1987, 1988, but a similar movement was noted in July 1963. Moths were probably in transit to summer aggregation sites in the nearby Absaroka Mountains of northern Wyoming.