PORTLAND — The Maine Forest Service wants Mainers to be on the lookout for an invasive beetle that has the potential to wreak havoc on the state’s maple trees.

The Asian longhorned beetle has already decimated tree-lined streets in Chicago and New York.

There is no reason to panic because the bug has yet to be seen in Maine, experts say. But experts want the public to keep its eyes open for the bug, which can destroy sidewalk plantings and sugar maple groves.

“It is a killer,” says Bruce Parker, an entomologist at the University of Vermont. “It has taken out trees, no question about that.”

The Maine Forest Service began distributing posters about the beetle this week. Emblazoned with the word “Wanted” in bold black letters, the posters feature a drawing and description of the bug, together with photos of damaged trees.

Vermont circulated the same poster last year.

“It’s much more destructive and aggressive than our native species are,” says Richard Dearborn, a forest service entomologist. “Once it’s got a foothold, it’s just about impossible to eradicate.”

Native to northeastern China, the beetle measures about 1 to 1 1/4 inches long, with 2-inch antennae. Its body is black with white spots, and its antennae are distinctly segmented with black and white bands.

The beetles infest various hardwood trees, but they seem to prefer Norway maples and sugar maples.