Hundreds of brown insects covered the outside of Karen Fallon's Newton home like a blanket and fluttered furiously around her porch lights. The crab apple tree in her front yard was also under siege.
''It was so strange. You could see them in the street. They were all over the house," said Fallon. ''I ran into the house and they followed me inside. It was really creepy."
Winter moths are taking the area by storm. Since late November, the male moths have been flocking in unprecedented numbers to some suburbs west of Boston, seeking their wingless female mates.
And while they're harmless to humans, the moths could pose a big problem for the area's trees.
In April, their offspring, a tiny green caterpillar, will feast on budding leaves in their favorite trees -- the crab apple, apple, maple, oak, and birch.
Last spring the moths ravaged the leaves on 22,000 acres of trees in Eastern Massachusetts, including those in the towns of Wellesley and Needham, said Jeff Boettner, a wildlife biologist at UMass-Amherst. He expects that number to reach 100,000 this spring.
The damage can weaken and even kill trees if it continues for several seasons.
The arrival of the moth, a newcomer from Europe that has no natural predators here, has sparked particular concern in the maple syrup and apple industries.
''This is the classic invasive insect story," said Robert Childs, a winter moth researcher and professor in the Department of Entomology at UMass-Amherst. ''It comes from another continent, it can survive in our climate, it has plenty to eat and there is absolutely nothing that controls it naturally."
The population of winter moths in Eastern Massachusetts has exploded to at least 1 trillion since they were first detected in December 2003.
The highest populations have been found on Cape Cod and in Plymouth and Essex counties. The moth has also made its way to Rhode Island, experts said.
''It's pretty widespread, mostly within the Route 495 beltway," said Boettner, who has deposited more than 40 traps throughout the state with hopes of better counting the winter moth population. ''This thing is going to really mushroom and get all over the place soon, unless we control it."
Experts do not know how the insect traveled to the Bay State from Europe. It first gained a foothold in North America in the 1950s, when it was detected in Novia Scotia. Washington state, on the other side of the continent, saw a winter moth invasion in the 1970s.
There is hope the population can be controlled, but it will take several years of hard work. UMass-Amherst entomologist Joseph Elkinton is breeding the winter moth's only known predator, cyzenis albicans, a parasitic fly that ats its victim from the inside out. The flies will be released in several locations throughout the state in May.
''Luckily, it's a problem we think we can fix and that's great news," Elkinton said. ''In Novia Scotia, it took six years to get it under control and our population is larger."
Until then, there are a few steps homeowners can take to save their favorite trees, researchers and tree experts said.
Pesticides can kill moth eggs laid in the trees if applied in the early spring before they hatch. But more eggs should be expected in crevices the spray cannot reach, calling for a second spraying.
Michael Lueders, president of Lueders Tree and Landscape Inc. of Needham and Medfield, recommends homeowners who want to save their trees seek help from a nursery, garden center or professional arborist.
Symptoms of sick trees include missing branches and a thin canopy of leaves, Lueders said. Fertilizer and water will help trees better deal with the stress of producing a new set of leaves.
''Unless a tree is under severe stress, one year of defoliation is not going to be a problem. But each year withdraws more energy from the tree," said Lueders, whose business began responding to winter moth problems four years ago.
''It's like a savings account. If you keep making withdrawals, but not deposits, it's just a matter of time before you run out."