Periodical cicadas spend the majority of their time underground as nymphs. Then, every 13 or 17 years, a whole group of billions of cicadas emerges together. The insects rush out all at once, completing one of the most unusual lifecycles in nature. But why do they do it, and how do they know when to do it?
Why cicadas have this peculiar cycle
Nature often operates with year-long patterns, where many organisms are attuned to the seasonal changes of the environment. Migration is a good example of this. Some predators also have natural cycles that happen every 2 or 3 years. So, cicadas, which are almost defenseless against most predators, found a way to take advantage of these cycles. They deviate from all norms and emerge at prime-numbered life cycles of 13 or 17 years.
These cycles are not only unusually long but also effectively desynchronize them from the cycles of potential predators and competitors. This essentially means no predator species can adjust to their cycles.
The cicadas have another advantage, although it’s not a very elegant one. To ensure enough of them end up surviving, they simply overwhelm with numbers. That’s why cicadas come out in such great numbers at such