A big event in the insect world is approaching. Starting sometime in April or May, depending on latitude, one of the largest broods of 17-year cicadas will emerge from underground in a dozen states, from New York west to Illinois and south into northern Georgia. This group is known as Brood X, as in the Roman numeral for 10. For about four weeks, wooded and suburban areas will ring with cicadas’ whistling and buzzing mating calls. After mating, each female will lay hundreds of eggs in pencil-sized tree branches. Then the adult cicadas will die. Once the eggs hatch, new cicada nymphs fall from the trees and burrow back underground, starting the cycle again.