If you want to make some money, listen to the sound of the Brood II 17-year cicada, emerging soon on the East Coast to do what all 17-year-olds try to do: look for a mate.

It also turns out that cicadas are decent market forecasters.

Going all the way back to 1928, a cicada year was good for stocks, according to Marketwatch. Brood II years posted a market gain of 21 percent. That’s about twice the historical average.

So think of that when they are crunching under your feet or dive-bombing you from overhead.