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Winter moths expanding west.

While wind, rain and cold have made most of this deer season rather beastly, we've been meanwhile privy to a relatively new insect phenomenon that's both fascinating and worrisome.

From about Thanksgiving through December -- whenever night temperatures have been above freezing -- our headlights have put the spotlight on the region's millions of mating winter moths. On some nights -- even rainy ones -- they've looked like a storm of pretty snowflakes. Though they're spritely and somewhat entertaining now, their progeny in caterpillar form will defoliate many of our local deciduous trees next spring.

The recently introduced winter moth is most numerous east of Interstate 495 where it has devastated much of Cape Cod's foliage the last several years. With the nocturnal stealth of a true villain, it has entered Worcester County, the frontier of its western expansion.

Winter moths were first introduced from Europe to Nova Scotia sometime around 1950. They've spread like a cancer. In Europe, they pose no environmental problem because abundant natural predators keep their numbers under control. They have no such natural predators here, so chemical warfare has been initiated as a last resort in areas most devastated by them.

The flying brown or tan moths are all males with distinctive fringing on their hind edge of their wings. The gray, flightless females have much attenuated wings, which necessitate their crawling up vertical structures from the ground to get attention. Similar looking fall cankerworm moths can emerge at the same time, but their females are wingless, and the males have an obvious light patch on the tip of their front wings.

Positioned prominently, the female winter moths release sexual pheromones to attract the cruising males. Soon after briefly mating, the females will lay their eggs in scattered patterns on the bark of trunks and branches, usually around or within bark crevices and scales. The lives of both sexes are ephemeral. Each dies shortly after mating.

The eggs will overwinter and hatch out anytime from late March to the third week in April, depending on whether we have a very warm or cold spring. The green larvae with a noticeable pale white stripe on each side of the body are immediately ready to voraciously eat the tender foliage and flowers inside the buds of their host plants. Entering through the bud scale margins, they do serious damage to maples, oaks, apples, cherries, basswood, crabapple, ash, and blueberry. During cold springs, like the one we had this past year, bud opening is delayed, and the larvae have more time to wreak havoc inside.

Local plants have already had to deal with defoliation from forest tent caterpillars and gypsy moths. Winter moths can provide a fatal coup-de-grace if they subject plants to four consecutive years of defoliation. Right now, oaks at Cape Cod -- weakened additionally by previous summer drought conditions -- have been showing signs of severe stress from their perennial attacks.

The tiny newborn caterpillars don't chew their way into the buds, but rather slip inside the opening scales. If they get into the flower buds of blueberries, they can wipe out the whole crop. By late May or early June, the fat, fully-grown caterpillars fall to the ground, where they spin a cocoon and pupate for six months. On and in the ground at that stage, they're immobile prey for some beetles. Those that survive their metamorphosis begin emerging around Thanksgiving.

During our very early snowfall in November, another phenomenal but little-known species, the snow flea, revealed itself. Looking like specks of dark pepper on snow, they can be seen only on warm days during winter, when they jump athletically. Forget about ever seeing them in summer. Without snow, they're invisible. The snow flea's ability to thrive under harsh conditions is the result of evolving an anti-freeze-like protein that keeps their cellular liquids from forming ice crystals even in below-zero temperatures.

A third amazing local species, the snow scorpion, also revealed itself after that last snowstorm. About half the width of your baby fingernail, they can sometimes be seen walking across the snow looking for a mate. Adapted for life in extreme cold, they die immediately upon being held in a warm hand. Not every creature likes it warm.

For those who take the time to carefully observe the outdoors, there are amazing displays of wildlife twelve months a year.


Wednesday -- Jackrabbit season closes on Nantucket and snapping turtle season closes statewide.

Next Friday -- Gray squirrel season closes statewide.

Contact Mark Blazis at
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Title Annotation:Sports
Publication:Telegram & Gazette (Worcester, MA)
Date:Dec 26, 2014
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