Scrolling down through the wikipedia page on "periodical" cicadas, my simplistic assumption that 17 year cicadas emerge everywhere in the same year was blown out of the water. There are many different "broods" in the U.S., each with a different timing. In any given year, there's a brood of 17 or 13 year cicadas emerging somewhere. Virginia has seven different broods. New Jersey has three. Princeton's cicadas are part of the "great eastern brood," which extends from New York down to Georgia and out to Illinois. Is it called great because the brood extends over such a large geographic area, or simply because Princeton is included? We don't know.
One thing's for sure, this will be the most photographed generation of 17 year cicadas ever. For the next month or two, while their bus-with-wings bodies fill the air outside, they'll also be zipping around in posts, texts and tweets.