National Geographic Daily News
Cicada exoskeletons clustered around a tree.

The cicada brood scheduled to emerge from underground this year could contain millions of individuals.

Photograph by Karen Kasmauski, Corbis

Daniel Stone

National Geographic News

Published March 29, 2013

Periodical cicadas (Magicicada septendecim), the cousins of katydids and crickets, have a unique breeding schedule, and after 17 years of living underground, a large group of them are preparing to fill the skies along the U.S. East Coast, from North Carolina up to Connecticut.

Normally, periodic cicadas spend their lives in complete darkness underground, sucking the fluid out of the roots of trees and shrubs. At the end of their life, they emerge, breed, and almost instantly die, completing a lifecycle that humans have studied for centuries.

In the process, however, they annoy millions of people with their constant chirping and, of course, the piles of dead cicada bodies on the ground. While some areas may see no cicadas at all, others in the past have seen millions of cicadas in a single acre. (Listen to the cicada’s love song.)

"It can be like raking leaves in the fall, except instead of leaves, it’s dead cicada bodies," said Dan Mozgai, a cicada researcher who keeps a clearinghouse of cicada information and breeding schedules at


Cicadas are easy to anticipate because of their extremely consistent mating behavior. Every 13 or 17 years, depending on the population, species of periodic cicadas will emerge as part of a specific brood in order to look for a mate.

The group expected this spring, known as Brood 2, are the offspring of cicadas last seen in 1996. If they follow the same tracks as their parents, they'll emerge in Connecticut, Maryland, North Carolina, New Jersey, New York, Pennsylvania, Virginia, and Washington, D.C.

The genetic mechanism that prompts periodical cicadas to emerge kicks in every 17 years (or every 13 years for other broods) when the ground warms up to 64°F (18°C).

Some researchers think the timing of a brood’s emergence is a defensive mechanism—appearing at infrequent intervals means that it’s harder for would-be predators like birds and squirrels to anticipate when the insects will be available to eat.

Others suggest that the 13- and 17-year cycles, prime numbers in mathematics, help cicadas avoid parasites. A 2004 study from the University of Campinas in Brazil suggested that a cicada with a 17-year cycle and a parasite with a two-year cycle, for example, would meet only twice each century.

But not all cicadas breed on this multiyear cycle. Some, like the tibicen cicadas, work on an annual rotation, leaving them more susceptible to predators like the cicada killer wasp (Sphecius speciosus).

The wasps know exactly when to expect the annual cicadas in late summer or early fall. The wasp lays its eggs on the cicadas, and the larvae slowly kill the cicada and feed off its carcass.


For the periodical cicadas, their temperature thresholds for emergence are getting harder to anticipate. During mild winters, like in 2012, cicadas from Brood 1 appeared in mid-April. Scientists think that this year, Brood 2 cicadas could wait until early May or even later.

John Cooley, a cicada researcher at the University of Connecticut, has led efforts to map where cicadas live, breed, and die. With funding from a grant from the National Geographic Society, Cooley has attempted to trace their evolutionary history since the last ice age, trying to understand how the species evolved as the world's climate changed.

"We know that they've had to change in the past because of postglacial forests that exist now," Cooley said. If scientists understand how cicadas once responded to climate change, then they can imagine how another episode of global warming might impact both cicadas and other insects.

In the meantime, the offspring of the insects that last appeared when Bill Clinton was President will soon be making their presence very well known.


They are HERE!!! Central Virginia - they are very lazy, laying just outside their shells - the shells appear like they're attached to plant life..  look out VA - I can see about 100 this morning - I see 2 on Mother's Day...What to do?

Alma Andersen
Alma Andersen

I really loved it the last time they were around.  Had to brush off my clothes to get into my car just walking thru the parking lot at work.

Amelia Day
Amelia Day

Very handy that we apparently are going to miss the invasion in Delaware, despite being surrounded by other states that will see them?  At least the bugs know where we are, even if NatGeo doesn't...

W.t. Davis
W.t. Davis 1 Like

Did you know the Staten Island Museum has the most diverse cicada collection in North America?   To celebrate the emergence of Brood II, the museum currently has "They're Baaack! Return of the 17-year Cicada" on display for public viewing.  If you're in the New York City area, please stop by to learn more about these amazing insect.  You'll find out about the various Broods which come out in different years, how distantly related to katydids and crickets they really are, and so much more!

Rachel Wilson
Rachel Wilson 1 Like

"Cousins to katydids and crickets" ? I thought cicadas were in the order hemiptera and crickets and katydids are orthopterans, a completely different order of insect. Did something change since I took entomology last semester??

David Rothenberg
David Rothenberg 1 Like

for the full story of periodic cicadas and the music of many more insects see

Jeff Moran
Jeff Moran

For a great song about periodical cicadas, set to a recognizable melody, please visit Dr Chordate's myspacemusic site, , and click on the Periodic Cicadas song. Thanks. Dr Chordate

Jeff Moran
Jeff Moran

For a great song about periodical cicadas, set to a recognizable melody, please visit Dr Chordate's myspacemusic site, , and click on the Periodic Cicadas song. Thanks. Dr Chordate

Matthew Utley
Matthew Utley

I'm not an entomologist but are cicadas really related to katydids and crickets, or was this conflated with the nickname "locust"?

Matthew Utley
Matthew Utley

I'm not an entomologist but are cicadas really related to katydids and crickets, or was this conflated with the nickname "locust"?

Robert Howle
Robert Howle

Have the annual type in my backyard, along with the killer wasp and all, plus I have the wingless wasp also know as the "velvet ant" also know as "cow killers". 

Have watched these wasp in action and they hover just above the grass waiting for the  emergence in late summer.  They have never bothered me even while I cut the grass.  Believe me they are vigilant.  

Dan Stone
Dan Stone

Thanks for the comments everyone. To respond to a few questions:

Miglena, the 2004 swarm was a different brood -- Brood X as they're known. That brood is also on a 17-year cycle, but not one that coincides with the Brood 2 cicadas that we'll see this year.

And James, sounds like you had a memorable wedding!

Dan Stone

Andrey Gonov
Andrey Gonov

It was during summer time about 50 years ago and my dad drove his car with open windows. As we move somewhere before Greece border in the car suddenly burst into a large gray bug as almond and landed on my shirt. My father said: This is krech ... you're lucky. This "krech" was cicada. Never then krech not seen, but I enjoyed the strange sounds they make. Now I really understand that I was lucky.

William Adcock
William Adcock

The Cicada Wasp are going to have a field day this year here in VA.

James Hayes Bohanan
James Hayes Bohanan

We loved having our wedding in a cicada season -- Baltimore in May 1987. We did not manage to get back for the next visitation, but I think I have an idea for our 34th anniversary in 2021!

Allie S.
Allie S. 2 Like

This was an interesting read. I always found the life cycle of cicadas to be quite fascinating. The small town I grew up in was always occupied with cicadas during the spring/summer. I'd camp out watching them emerge from their shells and remember how my grandmother taught me not to touch their wings til they dried. Lots of great memories tied into a great experience with such a neat species of insects.

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