Tens of billions of noisy cicadas are set to emerge from the ground in the coming weeks in a rare synchronized event that last occurred 221 years ago. The winged insects are expected to appear across the Midwest and Southeast starting in early May, in a double emergence of two different broods of periodical cicadas. These bugs spend a fixed number of years underground before surfacing to take part in a raucous mating ritual.
This year’s emergence is expected to be unusually large, with some experts estimating that more than a trillion cicadas could blanket parts of the country where the two broods overlap. Cicadas are harmless to humans, though some people find the sheer number of insects and their loud mating songs a nuisance. For bug enthusiasts, it’s a once-in-a-lifetime opportunity to experience the two cicada broods emerging together, given that it last occurred in 1803, when Thomas Jefferson was president.
This spring’s emergence will feature Brood XIII and Brood XIX cicadas. Brood XIII, on a 17-year cycle, typically appears in the Midwest, mostly in Illinois, though also in parts of Iowa, Wisconsin, and Indiana. Brood XIX cicadas, on a 13-year cycle, emerge over a much larger geographic area that includes Illinois, Missouri, Louisiana, North Carolina, Virginia, and Maryland. Seven broods of periodical cicadas make their home in North America, emerging every 13 or 17 years. A 13-year brood and a 17-year brood occasionally come out at the same time, but each specific pairing only sees their cycles align once every 221 years.
This year’s event is unusual because these particular broods are syncing up and also because they happen to be adjacent to one another, with a narrow area of geographical overlap in central Illinois. Daniel Young, a professor of entomology at the University of Wisconsin-Madison, notes there aren’t many places in the country where two very different broods overlap.
Thousands of cicada species can be found worldwide, but periodical cicadas are unique as they spend most of their lives underground, feeding on tree roots. After 13 or 17 years, depending on the brood, they emerge for a frenzied monthlong search for a mate.
Early sightings of cicadas haven’t been reported yet, but they usually emerge once soil temperatures reach around 64 degrees Fahrenheit. Some may start to appear in early or mid-May, continuing into June as conditions warm. Once out, researchers will gather specimens for study.
Cicadas are known for their loud mating songs, which can reach up to 100 decibels, and their mass emergence leads to a temporary cacophony. Despite the spectacle, cicadas don’t bite. Jeremy Louderman, a cicada enthusiast, hopes that this event sparks curiosity, much like a total solar eclipse, and inspires interest in entomology.
Researchers at the University of Wisconsin-Madison plan to track cicada sightings to map their range, encouraging public participation through apps like Cicada Safari or websites like Bugsinourbackyard.org or Bugguide.net. Young hopes people will embrace this rare event, especially in areas where the two cicada broods overlap.
“Not many people in human history are going to be in a place where they can witness that,” he said. “A lot of people may find it very unpalatable, but it’s a pretty amazing thing.”
