How Cicadas Work

This cicada is no longer living, but it's still beautiful on this leaf. Note: The cicada pictured is not a member of 2013's Brood II. See more pictures of insects.

Katherine Frey/The Washington Post via Getty Images

They are crawling out from underground, where they have been hiding in the darkness for almost two decades. They are invading the East Coast in the United States, as far south as North Carolina and as far north as Connecticut and New York, as of May 2013.

They fill the skies and forests as they swarm. Thousands of them cry out together day and night. They are Brood II. Should you be frightened? Should you try to prepare yourself?

Not really. The only preparation you may need to greet the cicadas of Brood II (or any other periodical cicada) is a pair of earplugs, because the worst they can do is keep you up at night.

Cicadas are flying, plant-feeding insects that are most famous for their powerful singing voices and rare appearances. Of course, not all cicada species dramatically appear en masse at regular intervals of 13 or 17 years. Some species feature adults that pop up on a more ho-hum annual basis.

But in spring 2013, the Brood II cicadas have come to perform once again.