Photo by Nikolas Knapp Miller moth

Courtesy Photo­Image Swallow

‘Miller moth’ is the term given to any type of moth that is abundant in and around homes. In Colorado and much of the Rocky Mountain west, the common ‘miller’ is the adult stage of the army cutworm, Euxoa auxiliaris.

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In some years, the millers become a serious nuisance, particularly during annual migration from the plains to the mountains in late spring, according to Whitney Cranshaw from Colorado State University Extension.

Miller moths get their name from the fine scales that cover the wings and easily rub off. The scales reminded people of the dusty flour that covered the clothing of someone who mills grain, according to information from Colorado State University.

The large numbers of moths are due to the recent mild winter, which led to high survival.

The moths emerge from cutworm pupae during early spring and summer, when the weather warms. They spend the summer in the mountains and return in the fall to lay eggs, often in alfalfa fields.

This year, moths have come to North Platte and all of central Nebraska after hatching in Iowa and Wyoming, said Dave Boxler of the West Central Research and Extension Center in North Platte.

Birds are natural enemies of the moths, especially swallows. Often, swallows swarm in the air around traffic intersections, aggressively feeding on the moths.

House sparrows and other birds also are found at these locations, feeding on wounded moths. The swallows likely gather at intersections because millers like to seek shelter in automobiles and emerge while cars idle at stop lights. Also, the millers are released if drivers open vehicle windows at intersections to let the moths escape, Cranshaw said.

Miller moths like to crawl into narrow spaces during the night, such as car doors, and rest in darkness.

The silhouette of a swallow is unmistakable with its sharply pointed, angled wings and forked tail. They are often seen darting swiftly across the sky, catching insects in midair, according to a California wildlife website.

Miller moths are currently migrating to the mountains for the summer, as it becomes too hot for them in Nebraska, Boxler said. They ultimately settle at higher elevations where they spend a few months, feeding on nectar and resting in sheltered areas. They stay in the mountains until late August and September, then return to lay eggs.

Other wildlife feed on miller moths. For example, they can be an important part of the grizzly bear’s diet in Yellowstone National Park. Grizzlies feed on the fat-rich moths that rest under loose rocks, Cranshaw said.

This report was first published in the May 23 print edition of the North Platte Bulletin. Be one of the first to be informed, read the Bulletin's print edition.