MADISON, Wis. -- Clusters of caterpillar nests in fruit trees are a common site in Wisconsin this time of the year.

University of Wisconsin entomologist Phil Pellitteri said that it's the work of the Eastern Tent caterpillar, which is having a moderate year in the Madison area.

The caterpillars won't kill trees, but they will take the leaves off.

"Just when the tree starts to show green leaves is when they start to hatch," he said. "At that time, you can even scrape them off with your fingers (because) the eggs … make the twigs look a little swollen, kind of like a black Styrofoam, kind of shiny-looking."

Pellitteri said that people can prune out the nests, spray them out, but there is no long-term damage from the nests.

"You know, if it's a crabapple in your frontyard, if you want to keep leaves on it you'll have to treat it," he said. "If it's out in the woods, don't worry about it. They'll survive the feeding just fine."

Pellitteri said that the caterpillars are a native species. They started feeding in the last month and will continue to do so for about two more weeks.