Swarms of cicadas are unexpectedly crawling out from under trees from North Carolina to New Jersey. The red-eyed insects are almost impossible to miss; they fly around lazily, plunking into backyard barbeques and crashing into cars. They litter the ground with their crunchy husks as they molt. Most noticeably, they chirp en masse for their mates, producing a relentless, shrill buzz that is recognized as a song of summer. And within a month they are gone.