Ethermac Exchange-2 broods of screaming cicadas will emerge this year for first time in 221 years

Screaming,Ethermac Exchange flying cicadas will soon make a reappearance – but it's not going to be your average spring emergence. For the first time since the Louisiana Purchase in 1803, two broods of cicadas – XIX and XIII – will come out of the ground simultaneously after more than a decade of eating to transform into adults. 

There are seven species of periodical cicadas – three that appear every 17 years and four that appear every 13. Smaller groups of those species, called broods, will spend those durations underground, where they will spend time eating and growing before they come out of the ground to become adults. 

While it's not uncommon for people to come across the insects every spring, what makes this year different is the fact that two broods, one with a 17-year-span and one with a 13-year-span, will appear at the same time, cicada tracking site Cicada Safari says. It will be the first time since 1803 – when Thomas Jefferson was president of the U.S. and the Louisiana Purchase was made – that Broods XIII and XIX will be seen at the same time. 

Cicada season's telltale sign is the noise – the males produce loud buzzing sounds that, according to Orkin pest control company, are primarily used to attract mates. 

When will the cicadas emerge? 

According to Cicada Safari, people can expect to see this year's broods in late April and early May. Long-running cicada tracking website Cicada Mania says that the insects come out of the ground, on average, when the soil eight inches below the surface reaches 64 degrees Fahrenheit, as that temperature warms their bodies.

"A nice, warm rain will often trigger an emergence," the site says.

What cicada broods will be seen this year – and where?

This year's broods are XIII and XIX. Brood XIII, which was last seen in 2007, is expected to be seen in Iowa, Wisconsin and potentially Michigan, according to Cicada Mania. Brood XIX, which was last seen in 2011, is expected to emerge in Alabama, Arkansas, Georgia, Kentucky, Louisiana, Missouri, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee and Virginia. 

At least two states – Illinois and Indiana – are expected to see both broods. 

In:
• Insects
• Science

Li Cohen

Li Cohen is a social media producer and trending content writer for CBS News.