MassLive reports (here): This summer, millions of cicadas from broods XIX (emerging every 13 years) and XIII (every 17 years) will both crawl out from underground and fly across the south and Midwest looking for a mate, according to Cicadamania, a website dedicated to tracking the insects. The last time these two broods popped out of the ground at the same time was in 1803.
The cool thing about most periodic cicadas is that they emerge in prime numbers of years, a pattern that has evolved partly (entirely?) because it makes it harder to be matched by predators’ year-by-year population swings. This fact has always tickled me.