id="article-body" class="row" section="article-body"> Periodical cicadas emerge from underground in the spring of their 13th or 17th year. Here, a periodical cicada nymph clings to a tree branch in Greenbelt, Maryland, on May 11. Jim Watson/Getty ImagesThe much-anticipated cicadas of Brood X … [Read more...] about Brood X cicadas start to emerge across the map: What to know right now