Those large moths, with their black-and-yellow-striped bodies and gray and pink wings, are back in Central Oregon, covering homes, flying (and crawling) along forest trails and sometimes even crunching underfoot.
The outbreak this summer of Pandora moths may be even greater than in 2017, when the moths blanketed the foul ball net at Bend Elks baseball games and converged on lamp posts all across the city.
“We will see at least as many, if not more,” said Rob Flowers, entomologist with the Deschutes National Forest. “We don’t know if it will be worse, but we expect there to be high numbers again.”
The reason for the recent spike in moths is because Central Oregon is in the midst of a multiyear outbreak, which typically occurs every two to three decades. The outbreaks last for six to eight years, when three to four generations of Pandora moths live out their two-year life spans from larvae to caterpillars to moths.
Flowers believes this year could see the most moths because U.S. Forest Service staff discovered a high amount of larvae in the forests in 2018. The Forest Service mapped 145,000 acres of pine tree damage in 2018 from the larvae, a larger than normal range of damage, Flowers said. The larvae feed on the foliage of pine trees.
“This could possibly be the peak moth year because there were so many larvae in 2018,” Flowers said.
With wingspans as large as four inches, Pandora moths are one of the largest American forest insects and are native to Central Oregon. The species is drawn to areas with pine tree forests and volcanic soil. They are also found in Arizona, California, Colorado, Utah and Wyoming.
The adult moths appear in July and August, and they lay eggs that stick to pine trees over the winter months and turn into caterpillars the following spring.
In Central Oregon, the moths are generally found from Crater Lake to Bend.
Like any moth, they are drawn to light. Flowers encourages people to keep their outdoor lights off at night to help keep the moths away.
“They will fly from the forest to your house,” Flowers said. “Bright outdoor lights are a beacon for them.”
Flowers believes this summer is year six in an eight-year outbreak. He expects to find larvae in the forests in 2020 and moths again in 2021, but not as many as this year.
Because the multiyear outbreaks occur periodically, they can be hard to predict, Flowers said.
The first recorded outbreak in Central Oregon was in the 1890s on the Klamath Indian Reservation. An analysis of pine tree rings in the Deschutes National Forest show that at least 22 outbreaks have occurred over the last 600 years.
“It’s not a regular event, so we can’t predict when it will happen in the future,” Flowers said.
After 2021, the region may not see a Pandora moth outbreak for at least 10 to 20 years, Flowers said.
Pandora moths have several natural enemies, causing an end to each outbreak. The moths often contract a virus, which infects the larvae and spreads through the population, Flowers said.
In addition, small mammals, birds and wasps eat the moths.
Those who don’t like the moths can take solace in the fact that they do eventually go away.
“We have to ride this out,” Flowers said. “The population will fall naturally.”
The moths pose no risk to humans or pets. Flowers said you can even eat them. But he recognizes they’re not for everyone.
“There are a lot of nuisances with them landing all over peoples houses,” Flowers said, “and they are a mess to clean up.”
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