Cicadas

Evolution made cicadas fatter, delicious and numerous. Predators eat cicadas till they're stuffed, and whatever left is enough to lay eggs for the next generation. The next generation emerges after 13 or 17 years because these prime integers rarely sync with other integers making it rare that they will breed in sync with predators, so predators won’t be able to adapt and prepare themselves for the next buffet. Therefore cicadas' entire survival strategy is to get eaten.