Try googling 'green June beetle grubs'.... I think they eat rotting wood or other organic material as grubs, but I didn't look into it too much so im not sure. There are a couple large beetles that they could be but the June beetle was the only one I could come up with. Actually there's a big scary black beetle that it probably is, but I can't think of a real name for it.... We just called them all June beetles! Lol
Good luck

.... Ok looks like the green j beetle is more southern PA and lives more in lawns. I've seen grapevine beetles around and they also have huge grubs.... Grubs that grow up in rotting stumps and other organic material. There's still one other big beetle I was thinking of, it's the big black one with big eyes and I can't seem to find it.