Prime Cycles: How 13- and 17-Year Cicadas Outsmart Predators

Two vast broods of periodical cicadas—Brood XIX (13-year) and Brood XIII (17-year)—emerged simultaneously across the eastern U.S. in 2024, the first such event since 1803, with next co-emergence not until 2245. The 13- and 17-year cycles are prime numbers, a fitness strategy explained as reducing overlap with predators’ shorter life cycles, a concept supported by predator-avoidance theory and, in part, by hybridization hypotheses. In mass emergences, predator satiation further boosts cicada survival, making these prime cycles a striking example of how a mathematical property can influence evolution.}