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!
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
@johncarlosbaez I remember a few years back being at the park and the Cicada noise was unearthly. A sort of hum you just don't hear normally. And it was loud.
@sullybiker - great!