This spring, for the first time since 1803, two cicada groups known as Brood XIX, or the Great Southern Brood, and Brood XIII, or the Northern Illinois Brood, are set to appear at the same time, in what is known as a dual emergence.
The last time the Northern Illinois Brood’s 17-year cycle aligned with the Great Southern Brood’s 13-year period, Thomas Jefferson was president. After this spring, it’ll be another 221 years before the broods, which are geographically adjacent, appear together again.
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Bruce
The last time the Northern Illinois Brood’s 17-year cycle aligned with the Great Southern Brood’s 13-year period, Thomas Jefferson was president. After this spring, it’ll be another 221 years before the broods, which are geographically adjacent, appear together again.
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Cicadas
extension.illinois.edu
Bruce
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