Moths swarmed across parts of Park County in recent days, but the good news is the abundance of insects should continue to taper off.

The surge in miller moth numbers could be attributed to very good conditions for survival and reproduction over the last year or two, said Scott Schell, entomology specialist with University of Wyoming Extension.

“Alternatively, the abundance in towns can be due to dry conditions out in the countryside with very few flowering plants available for the moths to feed on at night,” Schell said Monday. “The ‘normal’ population of moths are then drawn into irrigated landscapes and towns to find flowers and it makes them appear abundant.”

He thinks there’s a combination of those factors going on this year, “as the eastern plains had more reports of crop damage to alfalfa and winter wheat caused by the miller moth larvae, called cutworms, than usual.”

“That was followed up by dry conditions on the sagebrush steppe and prairie producing few wildflowers for the moths to gather nectar at,” Schell continued.

It’s an issue outside of Wyoming as well. Schell has read reports from Nebraska and Colorado of nuisance millers in towns at levels not seen for between five and 19 years.

As miller moths swarmed around Powell and Cody over the weekend, residents had theories about what caused the sudden increase. Some speculated the moths were migrating and just passing through the area.

“That theory has a grain of truth as the miller moths can migrate long distances to follow the peak bloom of flowers up into the high mountains,” Schell said. “However, some of the miller moths are also produced locally.”

“Where the moths that were ‘born and raised’ in the Big Horn Basin spend their summer is unknown,” he said, but a graduate student at Montana State University is trying to answer that question. Schell noted the local insects have mountains in all directions.

Schell is based in Laramie and has been collecting adult army cutworm moths — the most abundant species of the “miller moths” — for the graduate student’s research. The insects started showing up in Laramie back in early May through mid-June, he said.

“The starting point of miller migration all probably comes down to wind and weather,” Schell said. “A cold front from the north probably grounds the moths until it passes and warm breezes from the south are the ticket to travel a long distance in a night.”

By Sunday and Monday, the moth population had already dwindled in some areas.

“The miller moth abundance in town should be tapering off soon as the survivors will keep migrating to the high country,” Schell said.

While Powell has seen other times of increased moth populations, Schell said miller moths are not periodical like 17-year cicadas. The insects have an annual lifestyle, he said.

For residents dealing with unwelcome miller moths, Schell recommends turning off outdoor lights or switching to yellow bug lights during springs with higher numbers of the insects.

Although millers seem to be drawn to outdoor lights, “it is actually more a confused reaction than attraction,” he said.

Schell also recommends checking window screens and weather seals for cracks big enough for the insects to slip through; filling those cracks helps keep out moths when they seek out places to hide for the day.

“Check your screen door, as you don’t want to let in a whole bunch of millers into the house when you open the interior door in the morning,” Schell advised.

If the bugs do get into the house, he recommends using a vacuum to collect them “rather than swatting and risk squishing them on the wall,” he said.

For the miller moths that can’t be caught with the vacuum cleaner, Schell uses a night-light, set up over a dish of soapy water, to try attracting and trapping them.