Brood X of the periodical cicadas is largest cohort of cicadas that spend 17 years underground before rising, en masse, to molt, mate, and make a lot of noise. (Shown here is an adult next to its exuvia, or shed exoskeleton.) Scientists are looking to the public for help in mapping 17-year cicadas in the massive Brood X, due to emerge from the ground this spring in the eastern U.S. The citizen-science effort, powered by a smartphone app, could generate the biggest-ever observation dataset in the history of cicada research. (Photo courtesy of Gene Kritsky, Ph.D., Mount St. Joseph University)