Billions of cicadas are set to appear in a rare ‘double brood emergence,’ scientists say

In a matter of months, they will dig their way out from underground, red eyes shining, deafening song filling the air. It will be a confluence of creatures the likes of which hasn’t been seen in the United States since Thomas Jefferson was president — and won’t happen again until 2245. It’s a rare emergence of insects some are referring to as cicadapocalypse.

Billions of cicadas are expected to surface this spring as two different broods — one that appears every 13 years, and another every 17 years — emerge simultaneously. The 13-year group, known as Brood XIX, or the Great Southern Brood, is the largest periodical cicada brood, stretching across the southeastern United States. The Northern Illinois Brood, or Brood XIII, emerges every 17 years. “It’s rare that we see this size of double brood emergence,” said Dr. Jonathan Larson, an extension entomologist and assistant professor at the University of Kentucky. “We’re talking about an absolute oddity of nature, one of America’s coolest insects.”

Though the idea of a cicadapocalypse may seem foreboding, experts predict that the two broods won’t overlap significantly, and the bugs themselves, while loud and numerous, are harmless. Here’s what you need to know going into cicada season.