State biologists are seeking to study moths that are active in cold weather in an effort to learn more about the destructive insect.

The Maine Forest Service released a public advisory asking for help in an online survey to chart the sizes and locations of the invasive species known as winter moth, or operophthera brumata. Sightings should be logged at www.maine.gov/dacf/wintermothsurvey or by phone at 207-287-2431.

Information gleaned from the public is “very important,” Commissioner Walt Whitcomb said.

“These reports are critical to building the bigger picture of this insect’s distribution,” he said. “A healthy forest is key to Maine’s forest economy. Citizen involvement in monitoring invasive pests is important to the future of rural Maine.”

During the first week of December, the department’s staff will set up traps along the coast and inland in southern Maine, according to a news release. Towns in the study region are cooperating by allowing traps to be hung on municipal property. 

The moth flies when it is dark, and this time of year many people are still out after dark, the release said. Even if people are inside and glance out their windows, they may notice if there are small tan moths attracted to lights.

“The total economic impact of Maine’s forest industry is $8 billion with direct and indirect employment of 38,789 workers,” Gov. Paul LePage is quoted in the release. “Fighting invasive insects like the winter moth is important to help protect that sector of our economy; in this case, hardwood trees and agricultural crops such as apples and blueberries. Public involvement will help professionals combat and minimize the destructive potential of this and other invasive species.”

The winter moth was introduced into North America from Europe in the early part of the last century. It was first seen in Nova Scotia in the 1930s and then in the Pacific Northwest (British Columbia, Oregon and Washington) in the 1970s. Winter moth showed up in eastern Massachusetts in the early 2000s and has since spread westward in Massachusetts, into Rhode Island and now coastal Maine from Kittery to Bar Harbor. It was first reported in Maine in significant numbers in December 2011.

The larvae (caterpillars) of winter moth defoliate deciduous trees and shrubs such as oaks, maples, apples and blueberries, in early spring. Heavy defoliation for several consecutive years leads to branch dieback and tree mortality. Winter moth defoliation has contributed to tens of thousands of acres of oak mortality in Massachusetts.

Winter moth defoliation was first recorded in Maine in 2012. This year, the annual Maine Forest Service aerial survey picked up moderate to heavy defoliation in the Cumberland County towns of Cape Elizabeth, Chebeague Island, Harpswell, Portland (Peaks Island) and Scarborough with over 10,000 acres mapped. On the ground, light to heavy defoliation could be seen in scattered locations from Kittery to Rockland.

Adults are active from late November to January whenever the temperature is above freezing. Males are small, light brown to tan moths. They are attracted to lights and a chemical released by the females. Adult females are small, gray and look like a mosquito wearing a fur coat. They have reduced wings and are flightless. Females are most commonly found crawling on the trunks of trees. Those who see moths flying in December should let the Maine Forest Service know.