Periodical Cicadas Invade Missouri!

Those interested in mathematical explanations of physical phenomena should take note: May 15th is the predicted date for the emergence of swarms of the "Great Southern Brood" of cicadas, whose life cycle is 13 years. More details are provided by the Columbia Missourian:

Periodical cicadas survive on a strategy of satiating their predators. They emerge in such large numbers that there will always be some left over to reproduce. After a while, predators get tired of eating the cicadas and leave them alone.

“If you walked outside and found the world swarming with Hershey Kisses, eventually you would get so sick of Hershey Kisses that you would never ever want to eat them again,” Kritsky said.

The mathematical explanation answers the question: why is their life cycle a prime number?