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What is Brood X? When do cicadas come out in 2021? Answering your buggiest questions.

The Washington Post logo The Washington Post 4/1/2021 Bonnie Berkowitz, Artur Galocha

Sometime this spring, billions of cicadas that have been underground since 2004 will emerge en masse and blanket parts of the Eastern United States with their song and, eventually, their carcasses.

If you’re in the right location, they will be impossible to ignore.

diagram © Provided by The Washington Post Brood X cicadas are about to put on one of the wildest shows in nature. And D.C. is the main stage.

When do the cicadas come out in 2021?

That depends on the weather. This brood has been quietly rummaging around underground for the past 17 years and will not emerge until the soil temperature about a foot below ground reaches 64 degrees. Most will wait for a humid (but not stormy) evening to pop out of the tunnels they’ve been building for weeks.

They don’t all appear at once, but it may seem like it.

diagram © Provided by The Washington Post

Where will the cicadas emerge in 2021?

If you live in the D.C. area, lucky you! You’ll be in the middle of cicada-Palooza, where huge concentrations will emerge simultaneously.

People in other affected cities, such as Cincinnati and Philadelphia, will experience the insects as well, but New Yorkers may not. The last population in the state, on Long Island, was nearly extinct in 2004. The sandy soil was never a good fit for cicadas, said John Cooley, who leads the Periodical Cicada Project at the University of Connecticut.

map © Provided by The Washington Post

Researchers at Mount St. Joseph University in Ohio hope to map this year’s crop, and they have created a cellphone app so people can document cicada sightings where they live.

What is Brood X?

These cicadas are not the usual green ones that show up in some parts of the country every year.

a insect on a branch: A Brood X cicada waits for its wings to dry after its emergence May 11, 2004, in Silver Spring, Md. © James M. Thresher/The Washington Post A Brood X cicada waits for its wings to dry after its emergence May 11, 2004, in Silver Spring, Md.

Brood X — pronounced “Brood 10,” because cicada broods are labeled with Roman numerals — is one of the largest of 15 broods of periodical cicadas in the United States. (Three broods come out every 13 years and 12 come out every 17 years.) Three species make up Brood X, and they are known for their fire-engine-red eyes, their deafening choruses and their dramatic emergence every 17 years.

In 2004, this year’s cicadas hatched in small tree branches as tiny, translucent nymphs about the size of a grain of rice. They dropped to the ground and burrowed below, sucking liquid from plant roots, molting and growing.

Very soon, the now-plump nymphs will emerge from dime-sized holes in the ground and climb nearly any vertical surface. There they will molt one last time, breaking out of their brown exoskeletons as soft, white adults.

map © Provided by The Washington Post

The largest will be well over an inch long. Within hours, they’ll be at full color, and in a few days, they’ll be able to fly.

Adults cicadas live aboveground for two to four weeks and spend nearly all their time eating and trying to mate.

diagram © Provided by The Washington Post

How do cicadas make noise?

Only Brood X males can sing. They produce sound with membranes called tymbals, and their hollow abdomens amplify the call, but some of the details are still a mystery.

Each of the three species has a different set of calls.

diagram © Provided by The Washington Post

When a bunch of Brood X men get together, their chorus can reach 105 decibels — louder than a lawn mower. They may call to find others of their species, or to sound an alarm, but mostly they are trying to attract females.

Live like a cicada. Enter and exit singing.

Why do Brood X cicadas all come out at once?

Every species has a survival strategy. Some have killer claws or jaws, some have camouflage, some taste bad or spew poison.

Brood X cicadas, however, are lovers, not fighters, and those red eyes aren’t fooling anyone. Also, pretty much everything finds them tasty, from dogs and birds to reptiles and even some people.

Their superpower is sheer numbers. Scientists call it the predator-satiation defense.

It means they simply “overwhelm the predators by filling their bellies, and there’s still enough left over to perpetuate the species,” said Michael Raupp, an entomologist at the University of Maryland. There just aren’t enough predators to swallow them all before they reproduce.

Cicadas have an elaborate courtship ritual that, if a female deems a male worthy, ends in mating. Usually about an hour later, she will search for a tender tree branch, slice into it with her swordlike ovipositor, and lay eggs in the space.

The cicadas are coming, but gardeners need not panic diagram © Provided by The Washington Post

Six to 10 weeks later, tiny nymphs will hatch, drop to the ground, burrow below it and wait 17 years for their brief time in the sun.

Graphics editing by Lauren Tierney

About this story

Map data sourced from the University of Connecticut. Tymbal information referenced from Nahirney et al. Emergence timeline data sourced from Cicada Mania.


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