re: Cicadas are outta control

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Naw, they play an important role in soil fertility. These broods are large enough that their die off legitimately alters the ecosystem in a beneficial way.

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Their periodical emergence is interesting, and is still being studied by quite a few folks. The emergence on 13 and 17 year intervals isn't a happy accident. The fact that emergence of all periodcal cicadas occurs at specific intervals that are prime numbers is an important evolutionary development.

It has to do with predator availability. Most things in nature, especially breeding patterns and life expectancy, exist in a timeframe that revolves around even numbers. Predator satiation is why cicadas have evolved to emerge in such huge numbers. Their goal is to beat predation with shear numbers, predators just can't eat them all. That approach wouldn't work, however, if their emergence coincided with predictable population booms within predator species. It all comes down to the lifespan and mating habits of the predator species. By emerging on prime number years that don't coincide with population booms of predator species cicadas have evolved to center the mating aspect of their own lifecycles on times when the overall number of predator species is at their lowest in overall population.