For example, in 1999 a brood of 17-year periodical cicadas will emerge in the Ohio, Pennsylvania, West Virginia, Virginia area, and in 2000 one will emerge in Georgia, South Carolina and North Carolina. And what I remember most is the deafening sound that seemed to last a couple of weeks. And in some areas of Missouri, mostly south and east of Kansas City, they could overlap. The last co-emergence was in 1946, and the next won't happen until 2024. But they are not locusts.
Locusts are a type of grasshopper, but cicadas are related to leafhoppers and aphids.
About 20 species appear each year, emerging in mid- to late summer. But these 17-year cicadas are unique, not only because they spend 16.9 years underground feeding on the sap of tree roots, but because nearly every individual in the brood emerges during the same year every 17 years. There are almost no early risers or latecomers. Greenfield suspects that the extreme synchrony of the emergence serves as a defensive measure. Although birds and other animals will feast on them, the sheer numbers of them almost guarantee their survival from cycle to cycle.