Cicada double brood event: What to expect when trillions of bugs emerge in Eastern US

For the first time in 221 years, two gigantic broods of periodical cicadas are set to emerge from the ground simultaneously in the U.S. to engage in a raucous mating frenzy. 

The rare double cicada brood will include the two of the largest cicada broods, Brood XIII and XIX, which will co-emerge en mass after having lived underground for 17 and 13 years, respectively. 

Periodical broods are found only in eastern North America. When they finally emerge after a long juvenile period, they do so in enormous numbers. Once hatched, the immature periodical cicadas, known as nymphs, live off tree root sap underground before emerging in adulthood to mate — a noisy and frantic display that takes place over several weeks. 

This incredibly rare wildlife spectacle last occurred in 1803, when Thomas Jefferson was president, and it won't happen again until 2245. 

Although there are more than 3,000 cicada species, just seven are periodical cicadas (Magicicada). Of these, three have 17-year life cycles, and four have 13-year life cycles. Periodical cicadas have much longer life cycles than nonperiodical cicadas, which mature each summer and are found globally. 

When will the cicadas start emerging? 

Scientists at the University of Connecticut (UConn) have mapped cicada brood activity in the Periodical Cicada Project database, which shows that the double brood will begin emerging in late April 2024 and continue for several weeks.
 

How many cicadas could emerge at the same time?

"Billions, even trillions, of cicadas are going to emerge at the same time across 17 states," Chris Simon, a professor in UConn's Department of Ecology and Evolutionary Biology and one of the scientists who runs the database, told Live Science.