Screaming, 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.