WATERVILLE – Furry caterpillars are out in big numbers eating leaves and leaving their wispy weblike nests hanging from trees in Maine.

The so-called fall webworms show up every year about this time, but for whatever reason the numbers have spiked during the last couple of years, said Maine Forest Service entomologist Charlene Donahue.

When the numbers go up, it can take two or three years for the caterpillars’ predators to catch up in numbers, she said. But while the webworm nests are unsightly, the caterpillars are harmless.

“They’re not harmful at all,” Donahue said. “All they do is eat the leaves, and the leaves are going to fall off anyway, so rarely are the trees affected by them.”

The large unsightly silken nests typically begin appearing on branches of hardwood trees in late July. By late summer, the webs can become quite large and envelop entire branches.

The Maine Forest Service monitors the population levels of fall webworms and other insects with a network of 25 traps. Each night, the traps are emptied and the species are counted.

Most years in the spring, an average of eight to 10 moths that transform from the caterpillars are caught nightly. But last year, the traps caught the moths by the hundreds, Donahue said. This year, they were catching 25 to 50 a day.

It’s not known why the numbers have grown, but Donahue points to damp weather and healthy foliage as possible explanations.

The numbers probably will be high next year as well, she said.

Property owners who don’t like the unsightly nests can remove them by hand from small trees, or by using a stick or pole to twist them off the branches of larger trees. The nest can then be dunked in soapy water, killing the caterpillars.