Those conspicuous nests covering tree limbs across the region are home to a familiar pest.

Inside their silk tents, fall webworm caterpillars are busy doing what they do best — chomping away at leaves and the tips of tree branches.

While the insects are a common pest — making their annual appearance around August — this year their numbers are unusually high.

“It’s more than we usually see,” said forester Tim Cole, of the state Department of Conservation and Natural Resources.

“I think it’s because we’re about three weeks ahead as far as seasons go — we had that early spring,” Cole said. “They’ve had an additional three weeks to do their thing.”

Fortunately, according to Cole, the damage caused by fall webworms is less serious than other common pests — including eastern tent caterpillars and gypsy moths.

Eastern tent caterpillars, for instance, weave similar nests, but do so in the spring, when more damage can be done, Cole said.

Because webworms attack leaves in the late summer or early fall, the damage is often more cosmetic than harmful to a tree’s health, he said.

The insects feed on almost 90 species of our region’s deciduous trees commonly attacking hickory, walnut, birch, cherry, and crabapple, according to Penn State’s entomology website.

Robert Jacobs, director of the Centre County Planning and Community Development Office, said the nests shouldn’t be associated with gypsy moths, that destructive, invasive species that targets hardwood trees across the state and country.

This year, Jacobs said, a wet, cool spring helped develop a fungus that killed off the area’s gypsy moth population.

“We were concerned late last year that there would be a problem in the center and eastern parts of the county,” he said. “But there is really no issue this year. That’s good news.”

While the gypsy moth population is cyclical, the county predicts there will not be a significant enough population in 2013 to warrant spraying for the pests, Jacobs said.

Matt Carroll can be reached at 231-4631. Follow him on Twitter@Carrollreporter.