Hoosiers may have noticed a few more cicadas than normal this year.
Professor Keith Clay of Indiana University, who has studied cicada broods, says the cicadas appearing in Indiana now are four years early. Brood X typically surfaces every 17 years, and the next major emergence event isn't until 2021.
Clay says scientists don't actually know exactly what causes early emergence.
"There's several hypotheses that I can think of, none of which would be easy to prove or have been tested as far as I'm aware," he says. "One idea is that they're just mixed up. They weren't paying close enough attention."
Clay says the vast majority of Brood X won't emerge until 2021.
"I would think that what we're seeing is far less than 1 percent, maybe a hundredth of 1 percent, of what will be coming out in 2021," he says.
Clay says we've likely already passed the peak of the emergence event this year, and says most of the cicadas have now been eaten by predators.