Some 17-year cicadas maybe showing up a year early

CHICAGO (CBS) -- Some uninvited guests could be crashing your next barbecue.

Scientists say they are seeing cicadas pop up across the Midwest and South this year – including in the Chicago area.

The periodical cicada brood – known as Brood 13 – arrives once every 17 years to engage in a month-long mating ritual. During that ritual, they shed their skin, and in the words of researchers, "sing."

The 17-year cicadas appeared in 1973, then again in 1990, and once more in 2007. So that means they shouldn't be back until May of next year – 2024.

But it appears some can't wait.

The good news is cicadas are harmless, and not too many of the periodical cicadas will be around this year.

The periodical cicadas are different form annual dog-day cicadas – which come around every year in the Chicago area, and sing at dusk and sometimes even during the day between July and early October.