After spending 17 years underground, millions of cicadas will be emerging in parts of the United States. Periodical cicadas are expected to come out in early summer across southwest Virginia, parts of North Carolina, and in West Virginia. The last time the cicadas emerged in many of those regions was in 2003 and 2004, though some areas saw an emergence in 2013. As many as 1.5 million of the insects can emerge per acre of land. While they are some of the longest-lived insects in the world, periodical cicadas spend almost their entire lives underground as what entomologists call "nymphs".