In a few weeks, a natural spectacle will take place across much of the U.S. — one that is not found anywhere else in the world. The periodical insects, also known as Brood X, are back.
."And that's when they decide, you know what, it may be time to go up and find a partner."
Most of the world's over 3,000 species of cicada don't make quite as dramatic an entrance. While they take two to five years to grow up, at least some adults of these annual species show up every summer, and in much smaller numbers. In the natural sciences, it's called"predator satiation." After a certain point, even the hungriest predators wont physically be able to eat any more. But without a big synchronized group, the plan falls apart.Not all nymphs grow at the same rate. For example, one feeding from a tree that had a bad year will need more time. But if all the cicadas wait the full 17 years, it allows the unlucky ones to catch up and bolster the group's numbers.