Two U.S. Cicada Broods Emerge in 13- and 17-Year Cycles, Not Reuniting Until 2245
Updated
Updated · spacedaily.com · Jun 10
Two U.S. Cicada Broods Emerge in 13- and 17-Year Cycles, Not Reuniting Until 2245
3 articles · Updated · spacedaily.com · Jun 10
Summary
Brood XIX and Brood XIII surfaced together across 17 states in spring 2024, unleashing trillions of periodical cicadas in the first dual emergence of its kind since 1803.
13- and 17-year cycles are prime numbers, a pattern researchers say helps cicadas avoid syncing with predators whose shorter life cycles would otherwise overlap more often.
A competing model says prime-numbered timing also reduces hybridization: 13- and 17-year broods coincide only every 221 years, preserving the synchronized mass emergences the insects rely on.
Peak densities can top 1.5 million cicadas per acre, overwhelming birds, mammals and insects through predator satiation while adults mate, lay eggs and die within weeks.
Magicicada has 15 named broods—12 on 17-year cycles and 3 on 13-year cycles—making the insects a rare case where a mathematical property appears to shape evolution directly.