Rare Double Cicada Emergence Not Seen in 221 Years

Stock image of two 17 year Brood X periodical cicadas. This year, both the 17-year and 13-year broods will emerge at the same time.

In an extremely rare natural phenomenon, two different cicada broods will explode from the ground at the same time this year.

Some species of cicadas are periodical, spending most of their lives underground in their nymph life stage before emerging from the ground as adults to feed and mate. Millions of cicadas within the same brood can emerge at the same time, but this occurs only once every 13 or 17 years.

One brood—named Brood XIII—emerges every 17 years, while another, named Brood XIX, emerges every 13 years. This year, they will emerge at the same time, for the first time in 221 years.

Hannah Fry, a science communicator and mathematician, said in an Instagram video describing the phenomenon: “There’s one type that lives for 13 years, then there’s another one that lives for 17 years. It spends almost all of that time underground. The thing is, for extra drama, all of the cicadas are completely synchronized with one another, so every single 13-year-old cicada emerges from the ground, simultaneously flies around, has a massive party, sheds their exoskeletons, makes a massive mess, then dies.”

Fry said they do this because it helps to evade predators.

“There’s so many of them simultaneously that there’s no way the predators could eat all of them, so a massive proportion of them survive to the next generation,” she said. “Thirteen years and 17 years are special because they’re both prime numbers, which means it’s really hard for a predator to have a cycle that syncs up with them.

“Also, they almost never synchronize with each other—13 and 17—kind of missing each other, except for once every 221 years—13 times 17—when they’ll all appear simultaneously. The last time this happened was in 1803,” Fry said.

The last time that Brood XIII emerged was in 2008, while Brood XIX was last seen in 2011. This year, they will emerge at once for the first time since 1803, the year of the Louisiana Purchase.

These periodical cicadas are different from annual cicadas, which emerge from the ground every year. In a year when a periodical cicada brood emerges, the adults begin to appear during May and June and spend the next four to six weeks swarming around, attracting mates and coating trees in huge masses of eggs before they die. Millions of cicadas can erupt from each acre of the ground, resulting in billions of the insects suddenly swarming all at once.

Brood XIII contains several species of cicada, including Magicicada septendecim, Magicicada cassini and Magicicada septendecula, and will emerge across Indiana, Illinois, Iowa, Michigan and Wisconsin.

Brood XIX is found across Alabama, Arkansas, Georgia, Kansas, Kentucky, Maryland, Missouri, Montana, North Carolina, Oklahoma, South Carolina, Tennessee, Virginia and Louisiana, as well as Indiana, Illinois and Iowa. Therefore, both broods will be around at the same time across the latter three states.

The broods may cause damage to trees and crops during their time aboveground, as well as creating a loud buzzing noise and killing numerous other insects. However, they will soon die, often littering the streets with dead bodies. Their eggs will then hatch, and the nymphs will bury themselves in the ground for the next 13 or 17 years.

After this year, Broad XIX will next be seen in 2017, while Brood XIII will next emerge in 2041.

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