They're not locusts (which are a type of grasshopper), but for much of the Eastern U.S. this year, they're certainly a plague. Some cicadas appear almost every year, but the Brood X periodical cicada, as scientists call this variety , is the big one: the world's largest insect swarm. For the next five weeks, sidewalks will be littered with crunchy brown shells, ant treetops will be buzzing with an ear-splitting screech.
Cicadas look scary with their vaguely devil-shaped heads, but they're really harmless, and some communities even look forward to their arrival. Cincinnati, Ohio, for example, is planning cicada festivals,...