Big news in bug math. This is the first year since 1803 when both 13-year cicadas and 17-year cicadas will emerge from the ground simultaneously in the US!
13 and 17 are both prime. It's believed cicadas evolved to have prime-number life cycles to avoid predators that emerge more frequently, like once every 4 years or 5 years or... whatever. By showing up infrequently, with a prime number life cycle, they can starve out those predators.
And since 13 and 17 are both prime and 13 × 17 = 221, both kinds of cicadas emerge simultaneously only once every 221 years. And
1803 + 221 = 2024
so now they'll both emerge simultaneously and we'll have 𝑙𝑜𝑡𝑠 of cicadas!
Also, this year the two kinds can interbreed! Maybe they're be fruitful and multiply... and we'll get 221-year cicadas. 😆
The last time the Northern Illinois Brood’s 17-year cycle aligned with the Great Southern Brood’s 13-year cycle, Thomas Jefferson was president.
https://www.nytimes.com/2024/01/19/science/cicadas-emergence-broods.html