Metro

Winter moths make appearance for mating season

It’s that time of year again — the winter moths have arrived. And for some areas, researchers say the swarms will probably be thicker than last year’s.

The winter moth is in the midst of its mating season of late fall and early winter. Many of the insects appearing now are the same ones who chewed through the leaves of New England’s trees in the spring as caterpillars and then burrowed into the soil to wait out the summer.

The invasive European species, also known as the Operophtera brumata, has damaged trees from Long Island up into Maine. Scientists in the area are trying to understand how the species spreads — and how to control it.

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Residents who have seen clouds of drab-colored moths flitting around this fall are likely seeing only a portion of the population. Only male winter moths fly; females climb.

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“There’s almost no tree they don’t like,” said Joseph Elkinton, a professor in the department of environmental conservation at the University of Massachusetts Amherst. “It has an unbelievably wide host range.”

Elkinton studies several types of invasive forest insects and focuses on winter moths. His team is working to learn what factors affect winter moth populations across the region.

Though they will not receive data about this year’s population for another month, Elkinton said he expects this will be an “up” year in some areas.

“It’s up one year, down another year, up one year, and we don’t understand it,” he said. “We’re working really hard to figure it out.”

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In an experimental effort to keep the winter moths in check, Elkinton’s team has released thousands of Cyzenis albicans flies in 17 sites across New England, including sites in Massachusetts, Connecticut, Rhode Island, and Maine. Those flies only eat winter moths.

The team has monitored the spread of the fly in Wellesley, where Elkinton said the number of winter moths is now lower than in surrounding areas.

“This is something that takes time to get established. In any acre of land, you might have 10 million winter moths,” he said. “With any luck, we will soon, over the next five years or so, when we get the fly well-established across New England . . . the winter moth will be turned into a non-problem.”

Until then, Elkinton said, researchers are taking things one year at a time.

“We had high levels last year in many parts of Boston, so we don’t really know now whether the counts are up or down as to what we’ve seen last year,” he said. “It’s too early to tell, but from what I’ve seen, a lot of people are seeing a lot of moths.”

Felicia Gans can be reached at felicia.gans@globe.com. Follow her on Twitter @FeliciaGans.