Credit: UC Riverside The Eastern U.S. is about to see something that hasn't happened since the final episode of Friends aired on NBC: massive swarms of Brood X cicadas. Senior museum scientist Doug Yanega holds a collection of Southeast Asian cicadas at the Entomology Research Museum at UC Riverside. Credit: Stan Lim/UC Riverside Billions of the red-eyed, black-bodied insects are taking to the skies after 17 years underground, buzzing loudly to attract mates before they die. Not only is the spectacle of periodical cicadas unique in this country — it’s unique in the world, and biologists don’t really know why it happens.