If you’re a nature lover in parts of the eastern United States, you have a remarkable phenomenon to look forward to in 2024 – the emergence of not one, but two different broods of periodical cicadas. This incredible coincidence of cicada cycles hasn’t happened in well over 200 years.
What are periodical cicadas? Unlike the annual “dog day” cicada species we hear each summer, periodical cicadas belong to three species (Magicicada septendecim, Magicicada cassinii, and Magicicada septendecula) that remain underground as nymphs for either 13 or 17 years, synchronously emerging in massive broods.
Their deafening mating choruses are something to behold during their relatively brief above-ground adulthood of about 4-6 weeks. The males produce these loud, high-pitched mating calls by flexing their abdomen in and out while contracting drumming muscles to attract females.
The life cycle of these unique insects is truly astounding. After mating, the adult females lay their eggs in the tender branches of trees and shrubs. Once the eggs hatch about 6-10 weeks later, the tiny antlion-like nymphs drop to the ground and burrow, some up to 2 feet deep.
The nymphs then spend nearly two decades underground, slowly developing while feeding on xylem sap from roots. Once they reach their 17th spring, they construct exit tunnels to finally emerge near the trees and shrubs where they hatched nearly two decades earlier.
The double brood of 2024 In the spring of 2024, two distinct broods of 17-year cicadas will emerge simultaneously after developing underground since 2007 – a spectacle not seen in over 200 years. Brood X (the “Great Eastern Brood”) will blanket 15 states, from Illinois to New York to Georgia.
Meanwhile, the separate Brood XIV (the “Catawba Winery Brood”) will emerge in a narrower region spanning parts of Massachusetts, Maryland, North Carolina, and Tennessee.
The overlap zone of these two broods, mostly centered on Ohio, Pennsylvania, Virginia and parts of surrounding states, is predicted to experience a true cicada tsunami unlike anything witnessed in modern times.
Densities in this overlap region could reach an unbelievable 1.5 million cicadas per acre, according to predictions by Dr. Gene Kritsky, one of the world’s leading cicada experts and author of the book “Periodical Cicadas: The Plague and the Puzzle.” With numbers like these, the combined mating chorus of both broods could reach an incredible 100 decibels – similar to standing just feet away from a roaring motorcycle engine.
A once-in-several-lifetimes event Scientists estimate that the last time a double-brood emergence occurred was likely sometime between 1713-1718 or in the year 1800, based on detailed historical records and remains found in ancient Native American dwellings. No entomologists alive today have ever witnessed this unique convergence of 17-year cicada life cycles.
“The last time a co-emergence of these two broods happened, much of the modern United States was unclaimed wilderness,” says Dr. Kritsky. “Many people conflated these incredible events with Biblical plagues of locusts sent as omens and harbingers of misfortune. Of course we know today that cicadas don’t pose any threats – they are just incredible, fascinating organisms operating on vastly longer life cycles than humans can easily perceive.”
In fact, some Native American tribes like the Mohicans had traditions and stories venerating the periodic cicadas as symbols of rebirth and spiritual renewal, according to historians. Their mass emergences every 17 years may have reminded these peoples of the cyclical nature of life on Earth.
While a double emergence will create unprecedented densities that could potentially damage young trees and vegetation from excessive egg-laying, most experts agree this is a remarkably harmless event that should be embraced.
“Try to appreciate this as the amazing spectacle that it is – just nature going about its usual business, however strange and unsettling it may seem to us,” advises Dr. John Cooley, a cicada researcher from the University of Connecticut. “We’ll never see anything like this again in our lifetimes.”
Indeed, the next predicted overlap of Brood X and Brood XIV’s emergence cycles won’t happen again until the year 2245 – a mind-boggling 221 years from now.
So if you find yourself in the mid-Atlantic region in late spring of 2024, prepare for an unbelievable natural sound and sight show unlike anything you or arguably anyone alive has ever experienced. You’ll likely hear the cicadas before you see them, as their haunting, droning mating calls reverberate through neighborhoods and forests at deafening levels.
Just try to enjoy and appreciate the cicada chorus while it lasts – the next double brood isn’t expected for over two more centuries. And who knows what civilization will look like then, or if humans will even still be around to witness it?
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