BOSTON – They’re small, but they’re taking a big bite out of Massachusetts’ foliage.

Gypsy moth caterpillars are on the rise again in Massachusetts, prompting fears of a return of the massive invasions of the early 1980s that left trees stripped bare and houses covered with the crawling creatures.

Last year, the caterpillars defoliated about 60,000 acres. That’s about twice the damage of 1999.

Scientists believe the surge in population is related to a fungus that has kept the caterpillars in check in recent years.

They say the fungus might have become dormant, allowing the caterpillars to thrive. They are more worried the caterpillars may be building up a resistance to it.

The last great gypsy moth infestation occurred in 1981. The caterpillars chewed through 2.8 million acres of Massachusetts trees, more than half the state’s total area.

Some homeowners resorted to using garden hoses to spray the caterpillars off the sides of their houses.

“We may be back in this cycle of tremendous defoliation and some tree mortality in some areas,” Win McLane of the U.S. Department of Agriculture told The Boston Globe.

Gypsy moths, which got their names because they can spread over great distances, have a life cycle tied to the trees they devour.

Their eggs hatch in May and the larvae can blow for miles. They eventually settle on a tree, and do nothing but eat and excrete until late June or early July.

The caterpillars then spin a cocoon and emerge between mid-July and mid-August as a moth.

The effects of the caterpillars already are being felt this year.

At Nickerson State Park in Brewster, rangers are moving campers away from thick caterpillar droppings and the munching bugs have eaten most of the leaves on oak trees behind Bellingham Town Hall.

During the 1981 infestation, the caterpillar population eventually was cut down by chemical spraying and the fungus that attacks gypsy moth larvae.

With the fungus either dormant or the caterpillars building a resistance to it, environmental officials may have to consider spraying again.