Coloradans could see an influx of as the fluttering, dusty migration feels the impact of warm winter temperatures and drought during their journey from the Eastern Plains, across the Front Range and into the mountains.
Miller moths, or adult army cutworms, migrate to the mountains every spring in search of flowers for nectar. And while some years they appear to invade cities and towns along the Interstate 25 corridor, crowding around porch lights and sneaking through open doors, other years they are seemingly nonexistent.
It can be hard to predict how many moths will descend upon cities and towns in any given year, said Shiran Hershcovich, lepidopterist senior manager at the . (Lepidopterans are an order of winged insects that includes butterflies and moths.)
“We always get tons of questions on how many moths are going to come through, is it going to be a moth-y year?” Hershcovich said. “The truest answer is we’re going to have to wait and see.”
Karim Gharbi, extension agent with Colorado State University’s , predicts it’s going to be a more intense moth year for a few reasons.
“We had a really mild winter and larva have had more chances to feed over winter and it didn’t get that cold or wet, so fewer died from the freeze and more of them survived,” he said.
Colorado is also in a drought, which creates a ripple effect that affects even the moths. Fewer plants survived the winter, so there are fewer sources of nectar in the wild to feed the moths, which will push them toward communities where folks keep flowering plants alive with irrigation.
“I suspect there will be more moths overall, but also more near people’s homes,” Gharbi said. “They are annoying, but if you see miller moths, know your plants are getting pollinated and the birds around you are getting fed.”
Hershcovich agreed that moths are more likely to cluster near irrigated areas for their meals this year, particularly as they look for early-season nectar, and people should be prepared to share their space with the harmless insects.
“They really pose no danger and in fact contribute benefits to our natural spaces,” she said. “They’re pollinators, so they help plants reproduce, and they’re also an important food source for many other animals here on the Front Range.”
Even bears are known to munch on moths, Hershcovich said, as a “flying protein snack.”
Coloradans can support miller moth migration by turning off outdoor lights, which helps them stay on their migratory path, and making sure homes are well-sealed so the moths don’t get stuck inside.
“My final tip is always approach them with a little bit of curiosity,” Hershcovich said. “When we think of animal migration, we think of whales, elephants and monarch butterflies, but miller moths are also completing a very interesting animal migration.”
