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The 2021 Brood X Cicada Emergence: A Recap

periodical cicada

Entomologists who collaborated to create Cicada Safari, a mobile app to collect citizen observations of periodical cicadas, hoped they could get 50,000 observations during the Brood X cicada emergence in 2021. They got that, and then some: Nearly 200,000 people downloaded the app, and they submitted more than 560,000 photographs and 28,000 videos. (Photo by Annkatrin Rose via iNaturalist, CC BY-NC 4.0

Well. That whole cicada thing was quite the fuss, wasn’t it?

If you missed it a couple months back, a simple recap: The world’s largest emergence of periodical cicadas occurred this spring in the mid-Atlantic and eastern Midwest regions of the United States, with billions of them rising from the earth after a 17-year wait, making a bunch of noise, mating and reproducing, then swiftly dying. It all started in April and was over by the end of June. What’s left of them now are their eggs, which will hatch this summer (or already are in some places), at which point the nymphs will make their way back underground to bide their time until 2038.

It was a bonanza. For the cicadas themselves, for the birds and other animals that gorged on them, for the citizen scientists who observed them, for the media outlets and social media influencers that rode the wave, and—of course—for the professional entomologists who study them.

Entomology Today caught up with several entomologists who were busy with Brood X this year to get their thoughts on what they saw, what new discoveries may arise from data gathered during the emergence, and how this go-round compared to the last one in 2004.

A Perfect Storm for Citizen Science

Cicada Safari screenshot

Cicada Safari app screenshot (Image courtesy of Gene Kritsky, Ph.D., Mount St. Joseph University)

In April, we shared an early look at Cicada Safari, a mobile app developed by a cadre of cicada researchers and spearheaded by Gene Kritsky, Ph.D., dean of Behavioral and Natural Sciences at Mount St. Joseph University in Cincinnati, Ohio. Developed in conjunction with Mount St. Joseph’s Center for IT Engagement, the app allowed users to snap a photo or capture a video of their cicada sightings and upload them (along with date, time, and geographical coordinates, automatically) for mapping of the Brood X emergence.

At the time, Kritsky said he and colleagues were hoping to “go really big” and get 50,000 observations. Well, they got that, and then some.

“In total, over 196,000 people downloaded the app, and they submitted over 560,000 photographs and over 28,000 videos,” Kritsky says. “At one time during the emergence’s peak Sunday [June 6], over 8,000 people were using the app at the same time, and that day we received over 37,000 photographs.”

Considering how engrossing the massive cicada emergences are where they occur, the saturation of media coverage and social media activity on the subject, and today’s ubiquitous mobile technology, it’s easy to see how a citizen-science app with a simple task—upload a picture of an insect that’s easy to find—found broad adoption. Still, those numbers are impressive.

“The major surprise to me was how Cicada Safari became a story in itself, generating considerable international and national interest,” Kritsky says.

So Much to Study

What to do with that trove of data, plus all the direct observations researchers made in the field themselves?

Chris Simon, Ph.D., professor in the Department of Ecology & Evolutionary Biology at the University of Connecticut, says she and collaborators who had a hand in Cicada Safari are working on a paper now that will compile the observation data from the app (both for Brood X this year and Broods VIII and IX from the past two years), observations contributed via UConn’s cicadas hub, and other sources. She’s also working on a National Science Foundation grant proposal with several colleagues in the U.S. and Japan to sequence the complete genomes of seven species of periodical cicadas and model the effects of climate change on their lifecycles.

Simon’s UConn colleague John Cooley, Ph.D., says he hopes the new data will illuminate if and how Brood X’s geographic boundaries have changed. “It’s an ongoing question how much, if any, these boundaries change in the short term, though it’s obvious that they must change in the long term, since they are living in formerly glaciated areas,” he says. “Understanding change will better help us determine whether anything that we’re seeing can be explained by global climate change.”

Mike Raupp, Ph.D., professor emeritus in the Department of Entomology at the University of Maryland, says he will use data from Cicada Safari to compare the emergence of Brood X outliers that emerged a year early in 2020 in the greater Washington, DC, region to those that appeared this year.

And Zoe Getman-Pickering, Ph.D., postdoctoral scientist in the Department of Biological Sciences at George Washington University, reports she and colleagues at GWU and other institutions are exploring a host of research questions on cicadas, including how the cicada emergence perturbs oak forest food webs, if cicadas prefer certain hosts for oviposition and how that affects different tree species, and measuring the density and scope of the cicada emergence based on residual emergence holes in different habitat types, to inform how past and future land use change might affect the Brood X population size.

periodical cicadas

Entomologists say the Brood X periodical cicada emergence of 2021—and the incredible volume of observations logged via the Cicada Safari mobile app—will open up a host of research avenues, exploring areas including how climate change affects their lifecycles, how their geographic ranges are changing, why some brood members emerge early or late, and how their egg-laying affects different plant tree species. (Photo by Pennsylvania Department of Conservation and Natural Resources – Forestry, Bugwood.org)

A New Environment for Science Communication

Part of the fun of a periodical cicada emergence is simply thinking about how the world has changed in all that time the cicadas spent underground. When Brood X last emerged, President George W. Bush was running for a second term as president, and the Detroit Pistons were on their way to a 4-1 series victory over the L.A. Lakers in the 2004 NBA Finals. More important, though: The Cicada Safari app wasn’t even possible in 2004 (the iPhone debuted in 2007), and likewise the social media and online media revolutions were just beginning (Facebook was still “thefacebook.com” at a handful of universities in June 2004, and Twitter launched in 2006).

Kritsky, Simon, Cooley, Raupp, and Getman-Pickering—among many other entomologists—say they fielded countless media requests, from outlets across TV, radio, print, blogs, podcasts, and even filmmakers. And their outreach efforts diversified, as well. Kritsky’s team built an accompanying website for the Cicada Safari app, and Getman-Pickering and colleagues did likewise with their Friend to Cicadas site, which offered FAQs, photos, an educational workbook, art, and even a haiku contest. At the University of Maryland, Raupp led a graduate course in science communication in which the students built out a website and conducted online outreach via YouTube, Twitter, Facebook, and Instagram, in addition to dozens of interviews with national and local media outlets.

Raupp says Brood X seemed to receive a more welcome reception this year than in the past. “One huge difference I saw this time was the very positive ‘spin’ media placed on the entire event,” he says. “There was very little ‘OMG, here comes the plague’ and much more ‘OMG, cicadas are so cool.’ So, my thanks to many entomologists, naturalists, and journalists that made this a very positive event.”

Other Observations

According to Kritsky, the first sighting of adult Brood X cicada to emerge from the ground and be reported via Cicada Safari came on March 3. That was way ahead of schedule, as cicada emergence is trigged when ground temperature warms, but there was a simple explanation: “It emerged inside a tent with a hot tub,” Kritsky says.

Once the emergence began in most areas, some cool weather in May slowed things down in some places. Simon says a rainy Memorial Day weekend gave her a chance to see cicadas emerging in suboptimal conditions. “I was surprised to see nymphs able to eclose at 12 degrees Celsius temps with a light drizzle, but instead of taking one hour to get out of the shell, they would take something like five hours, and then the cuticle hardening/tanning process took place much more slowly, increasing the cicadas’ vulnerability.”

Raupp’s neighborhood in Columbia, Maryland, is right in the heart of Brood X country, and on several occasions he invited reporters and news crews doing stories on the cicadas to visit him there. He says his neighbors’ yards such as the one in this segment with ABC’s World News Now (screenshot above) are “surely the most viewed landscape of cicadas in the world. … The neighbors had lots of fun with this.”

University of Maryland entomology professor Dan Gruner, Ph.D., centered his spring “Principles of Ecology” class on the cicada emergence, with students measuring soil temperatures in anticipation of Brood X’s arrival. “Many students were having a difficult time in their third semester under pandemic lockdown, so I think they felt some empathy for the momentous occasion as the cicadas clawed their way from belowground in the spring,” he says.

Elsewhere, in a scene that likely occurred all across the Brood X range, cicadas were an object of fascination for one young entomologist (pictured above), whose mother, Karen Maguylo, shared that her son “collects the cicadas and tries to find their tymbal or ovipositor to figure out if it’s male or female. If that fails, he gets it to make a sound to figure it out.”

Finally, as we cap off the 2021 edition of Brood X, we can remember them with a song, by entomologist Samuel Ramsey, Ph.D. May this tune be playing in our heads until 2038.

1 Comment »

  1. Happy to meet my new favorite entomologist, Dr. Sam! One thing I found interesting in my yard was the remarkably decided preference for Crataegus viridis ‘Winter King’ over oak, dogwood, redbud, beech and many others for a general hangout spot though not for egg laying. Sorry to see not a word addressing the “perfect storm” of oak mites plaguing the DC met area. I recall none from 17 years ago. I understand the source is a European import that found its way here in the 1990’s – though perhaps not to the DC area until after the last brood. Can you please send it back?

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