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Billions of Brood X crickets appear for the first time in 17 years: what to know


Periodic crickets emerge from the ground in the spring of their 13th or 17th year. Fifteen US states, and Washington, DC, are about to see a whole lot.

Getty images

Parts of the eastern United States are about to witness a remarkable spectacle: billions of crickets tunneling out of the ground for the first time in 17 years to fill outdoor spaces and share their inescapable mating sounds.

Periodic crickets, as they are known, are different from annual crickets. They spend almost their entire life a few meters underground and live on sap from tree roots. Then, in the spring of their 13th or 17th year, adult cicada nymphs emerge for a short adult stage, synchronously and in great numbers. Really huge numbers.

A newly emerged periodic cicada sheds its exoskeleton and unfolds its wings. Soon it will be mating season.

GIF by Leslie Katz / CNET

The insects climb on the nearest vertical surface, often the tree whose roots supported them. They shed their exoskeletons and blow their wings. After resting for a few days and waiting for their shells to harden, mating begins. The frenzy is impossible to miss once the males start broadcasting their high-pitched mating song. This is done through sound-producing structures called tymbals on either side of their abdomen.

“They can gather … in parks, forests, neighborhoods, and can seemingly be anywhere,” explained Michigan State University entomologist Gary Parsons in an MSU question and answer session on the phenomenon. “When they are so numerous, they fly, land and crawl everywhere, also occasionally landing on people.”

Here are answers to some of the most important questions about the rise of great cicadas in 2021.

What is Brood X?

The eastern United States is home to six species of periodic crickets that emerge in different years. Groups of crickets that share the same emergence years are known as broods.

This spring, it’s time for members of one of the largest broods of 17-year-old crickets, dubbed Brood X or the Great Eastern Brood, to crawl out of their subterranean hideouts and show off their black bodies and bold red eyes. Expect to see all three 17-year-old strains: Magicicada septendecim, Magicicada cassini, and Magicicada septendecula.

Which states will be affected?

Parts of 15 states, as well as Washington, DC, will hear the romantic serenades of males in trees trying to attract females. The states are Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia.

When do the crickets emerge?

cicada safari

With the Cicada Safari app, citizen scientists can help map the insects.

Cicada Safari

The return of the crickets usually begins around early to mid-May (sightings of adult crickets have been reported in Georgia, North Carolina and Southeast Tennessee) and continues through the end of June. Needless to say, it’s a pretty sight. Some people consider the mass of insects to be one annoying annoyance, but others welcome it as an awe-inspiring natural wonder. Some in the latter category even regularly travel across the US. to cicadas emergence areas to experience the sights and sounds and help scientists map the creatures.

“It’s great because you’re surrounded by thousands, maybe millions of these creatures who weren’t there the day before,” said Dan Mozgai, one of those citizen scientists. “It’s like an alien invasion, like being in a movie.”

A free app created at Mount St. Joseph University in Cincinnati called Cicada Safari and available for iOS and Android lets the cicada-curious record periodic cicada sightings. They can also record sightings on the Cicada Mania and iNaturalist websites, a joint initiative of the California Academy of Sciences and the National Geographic Society. Cicada mapping helps scientists verify the periodic life cycles of insects, as well as their relationships with each other, to gain a better understanding of biodiversity, biogeography and ecology.

Because Brood X occurs four years after Brood VI and four years before Brood XIV, and because the three broods are adjacent in parts of their geographic range, cicada trackers may see “laggards” of other broods this year.

“From a biological perspective, four-year laggards of each of these broods are interesting because they can cause gene flow between them,” explains the University of Connecticut. “From a practical standpoint, the four-year laggards of all these broods complicate mapping efforts because it can be difficult to assign populations to a brood.”

Laggards may confuse map efforts, but the university insists that a “misleading map is worse than no map at all.”

Why are so many coming out at once?

It is thought that by emerging in such large numbers, enough of them can live on to mate – in fact, force in number.

The crickets usually start hatching when soil temperatures reach 20 inches below ground to 64 degrees Fahrenheit (18 degrees Celsius). “That seems to be the trigger that makes them all show up in one area within a few days or weeks,” says Parson. A warm rain often causes their emergence.

Because periodic crickets are sensitive to climate, patterns of different broods and types reflect climate change, note John Cooley and Chris Simon, professors of ecology and evolutionary biology at the University of Connecticut.

“For example, genetic and other data from our work indicates that the 13-year-old species Magicicada neotredecim, found in the Upper Mississippi Valley, originated shortly after the last Ice Age,” they write in a piece for The Conversation. “As the environment warmed, 17-year-old crickets consecutively emerged in the area, generation after generation, after 13 years underground, until they were permanently shifted into a 13-year cycle.”

How does the male mating call sound?

It varies by species, but it can sound like a high-pitched electric hum, a chirp, or a rattle (hear it below). The call of a group of men can be over 90 decibels, about the same level as a motorcycle about 8 meters away. The females respond to the males’ calls by clicking their wings, and all the back and forth movement creates a distinctive symphony.

Listen to the 17 year old crickets

Can crickets hurt me?

No, the insects are harmless. They do not sting, bite or carry disease, and they usually do not enter, although they do collect on outside walls.

“The only way they could get in is accidentally fly in through an open door or window, or because they landed on a person who then carried them in unnoticed,” said Parsons.

However, during dense emergence, females can lay enough eggs in branches to damage young trees. Here is more about crickets and your garden. And here is everything you need to know about crickets and pet safety.

How long will Brood X last?

Mass mating takes at least three to four weeks. Shortly after, the newly hatched nymphs will crawl to the edge of the tree branches where the females laid their eggs, fall to the ground, and burrow for the next 17 years. And so the cycle begins again. Godspeed, Brood X.

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