There are different "broods" of 17-year cicadas in different areas, that emerge in different years, and the same is true of 13-year cicadas. And sometimes some of them will emerge early. Plus, there are annual cicadas that are around every year. When I was out at Elmer Davis the other day, I saw sloughed cicada exoskeletons all over the place. I would think that fish would eat cicadas readily; everything else seems to. While they're emerging, maybe a surface lure that imitates a floundering bug might be a good idea?