Winter Moth Invasion: Stonehill Professor Explains Their Arrival To New England

December 10, 2015

They are everywhere on campus and beyond right now, plastered on external walls, doors, and pillars—huge numbers of Operophtera brumata, or winter moths.

An invasive species, the moths are native to Europe and somehow were introduced to Nova Scotia in the 1930s. They reached Massachusetts around 15 years ago and are now commonplace in New England, usually between mid-November and early January, according to Nick Block, assistant professor of biology who specializes in evolutionary biology and ornithology.

While not a threat to humans, the moths, Block explains, “can damage a wide variety of native trees, particularly maples, oaks, and fruit trees."

"The moths seen flying around are all males; the females are flightless and are typically found crawling up tree trunks," Block notes, "Following mating, the females lay eggs in crevices throughout a tree. When the eggs hatch in early spring, the young caterpillars devour new leaf and flower buds, damaging a tree's ability to reproduce and photosynthesize. If this damage persists over multiple years, the moths could put trees in such a weakened state that the trees could not survive even relatively mild threats to their health."

Moths can handle pretty cold temps by staying inactive, and Block reckons they're only active on days when it's above freezing.

"As long as we don't get a really deep freeze, we could still see some flying in January on relatively mild days. Their peak time seems to be around the last week of November, though, so their numbers will only decrease from here," he adds.