Miller moths have arrived in Colorado. The damp weather may prolong their migration
The westward miller moth migration — a familiar yet short-lived nuisance — may be prolonged by damp weather after an unprecedented month of rain in the state, and specifically in Colorado Springs.
For the storm of paperclip-sized moths that arrived over the weekend, Colorado Springs is merely a pitstop in their migration west. Colorado State University research associate Chuck Harp says the moths are attracted to the city lights during what would otherwise be a direct trip.
“If not interrupted by house or city lights, they’ll make their journey up into the mountains as they’ve done for all of history,” said Harp, a moth and butterfly expert. “They would prefer an uninterrupted flight into the mountains where conditions are cool and dry.”
Miller moths, the adult stage army cutworms (Euxoa auxiliaris), originate in eastern Colorado fields and areas of western Kansas and Nebraska. Between May and June, they spend weeks migrating westward to follow flowering plants for nectar before making a return journey in the early fall.
Harp called this year’s migration an “early flight,” meaning moth activity should settle down by early June. But, as in just two other years in the past decade, the moth migration is “severely” impacted by damp conditions, which Harp said prolongs travel.
Last week, a record 3.18 inches of rain fell in one day in Colorado Springs, bringing precipitation totals for a midweek storm to 3.77 inches, according to the National Weather Service — 3 inches more than normal for the whole month of May.
Increased moth sightings typically occur after a lack of moisture in the fall, winter and spring across Colorado and states along its eastern border, and over half of El Paso County is under “severe” drought conditions. If drier months lead to fewer blossoms, the moths may opt for manually irrigated areas like gardens, yards and other urban settings.
But the miller moth — which Harp said gets its name from early settlers who thought the moth’s scales (when shed) resembled grain mill dust — is mostly attracted to light and heat in homes and automobiles.
Harp recommends shutting doors tightly and turning off lights to keep the insects out of homes. “If they get into a home, they are likely to stay until they can escape or perish after a few days,” he said.
Moths also seek out cool, dry and dark places: Small cracks in doorways, garages and cars make ideal hiding spots to avoid daylight before resuming activity overnight.
Faced with a dearth of flowering plants in the eastern plains and beyond, miller moths seeking nectar will descend on Colorado for the next several weeks, expert say.
Closeup photo of a Miller Moth.