May 11, 2004

» Cicadas, which tend to swarm every 13 or 17 years — like Brood X appearing right about now — may do so to avoid a cycle that matches predator's lifecycles

Gould, a polymath who died in 2002, was among the first to propose that the cicada's unusual lifestyle is a strategy it evolved to avoid its predators.

"Some individuals hide, others taste bad, others grow spines or thick shells, still others evolve to look conspicuously like a noxious relative," Gould wrote. Periodical cicadas, he argued, did it by evolving a highly unusual reproductive cycle.

By springing forth from the ground by the millions, cicadas help ensure that no single predator can devour them, a tactic that evolutionary biologists now call the "predator satiation" strategy.

And by emerging every 13 and 17 years, Gould argues in his 1977 book, cicadas minimize the chance that their infrequent invasions will sync with the life cycles of birds and other creatures that dine on them.