Miller time: Moths take over Wyoming’s Big Horn Basin

By Leo Wolfson, AP

CODY, Wyo. (AP) — Cody resident Luke Hopkin said it is the most miller moths he has seen on his Sage Creek property in about 25 years. When he opened his garage the other day, thousands poured out in a black cloud.

“There was a crazy amount,” he told the Cody Enterprise.

Even after killing more than 1,000 moths over a three day period, he said he’d made no dent in the population.

“The weather is just right for them to be super happy,” he said.

If you noticed an uptick in miller moths over the past few weeks, you’re not alone. The moths have been invading homes, cars and even garages in mass clusters.

Scott Schell, a University of Wyoming extension entomology specialist, said certain weather trends over the past year or so paved the way for a massive miller moth population. He said last year’s wet spring and summer helped foster large moth populations. Those conditions were followed by this year’s mild winter and drier start to spring, bringing moths into the lower elevations – and towns – in search of pollination.

Schell said he has been receiving calls from all around the state reporting an influx of the miller moth. In Sublette County, the moth’s larvae – the army cutthroat worm – decimated a large patch of cheatgrass. In southeast Wyoming, Schell said they have been gathering in large numbers since mid-May. Reports of the moths in Colorado follow a similar timeline.

Josh Shorb, a district supervisor for Park County Weed and Pest, said he’s been receiving calls from concerned residents locally who have been finding moths in tiny nooks and crannies in vents and fans, fluttering wildly when lights are turned on. When crushed, a film-like substance comes off their bodies.

“It’s kind of messy,” Shorb said. “Then, when you break one of their wings you have a hurt moth in your lap.”

Thankfully the moths serve as no more than a nuisance and will not damage crops.

“Some people are deathly afraid of moths and have a hard time coping with them,” Schell said.

Hopkin said he uses flypaper and water traps to catch the moths that get into his home. In order to draw the moths away from his garage, he uses high-powered work lights, which the moths are naturally attracted to. He said pesticides have little effect on them.

The cooler weather seen over the last few days has caused the moths to become more dormant, but warmer weather this weekend could bring a resurgence of activity from the winged creatures.

Schell said by the end of June the moths should be mostly gone as they make their annual pilgrimage to the high country for the seasonal bloom there.

In the mountains, the moths feed on plants that produce nectar and stay open at night, including blackcurrant and burning bushes, sand cherry, Russian olive, spiraea and rhubarb.

One predator that should benefit from the increase of moths is the grizzly bear. Schell said the bears can be seen flipping rocks endlessly in August, seeking out the moths that shelter underneath. The moths can serve as a valuable source of calories for the large carnivores.

“A bear might eat 30,000 of them,” Schell said. “It would be like us popping sunflower seeds all day.”

A variety of songbirds like sparrows, robins and flycatchers also enjoy the critters and can be seen picking the bugs off vehicle grills.

“That’s a valuable nutrient for their nestlings,” Schell said.

The moths will come back down to lower elevations in the fall and lay their larvae on plants and crops like winter wheat and alfalfa.

Shorb said by keeping windows and other openings sealed, people can prevent moths from infiltrating their lives.

He also said the moth’s predators will soon catch up to the growth cycles, casting a setting sun on their dynasty.

“All native species have an up-and-down relationship,” he said. “The millers are at the top of the crest. The predators, they’ll catch up, and the miller population will crash.”

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