A Cicada Postmortem: What We’re Learning From Brood X

The insect chorus once audible through a triple-pane window is down to an occasional, lonely buzz in the treetops. All that’s left of the massive swarms recently visible on National Weather Service radar is a few squished bug bodies you need to pry out of your car’s radiator.

Yes, the cicadas of Brood X, which made our region into their strange kingdom for the last month or two, are mostly gone, but they’ve left behind billions of eggs that will hatch tiny nymphs next month to burrow into the soil and emerge in another 17 years—and new questions and answers that could keep scientists busy for much of that interim.

The University of Maryland’s Mike Raupp, professor emeritus of entomology and UMD Extension specialist known as “The Bug Guy,” has been in at the center of a global media crush for months, but as the last few adult cicadas fall to the ground to fertilize the trees, he took a break to talk to Maryland Today about the bounty of science emerging from the latest … emergence. Here are few takeaways:

We’re getting a clearer idea of where cicadas call home
Sure, there was little mystery that THIS area was thick with the red-eyed bugs. “Anecdotally, what I’ve heard from many, many people is this was kind of a banner year for the cicadas … my impression is that they were certainly more abundant in my neighborhood,” Raupp said. 

What was new for the 2021 emergence was a far more systematic, technology-enabled effort to track Brood X’s location, in large part through the Cicada Safari app, the main tool of a research project based at Mount St. Joseph University, with collaborators including UMD. This year, for instance, cicadas were spotted for the first time in Talbot County on Maryland’s Eastern Shore.

Hot on their trail of Brood X
A related frontier of scientific knowledge about the giant bugs is the role that soil temperature plays in the timing of their emergence. UMD undergrads got to help build that knowledge this year in an ecology class taught by Daniel Gruner, an associate professor of entomology, that had students monitoring soil temperatures in areas where cicadas surfaced in droves in 2004, and noting how it influenced when they finally emerged from their holes. “Next time around we’ll be able to much better predict where cicadas are appearing and when they’ll appear,” Raupp said. 

Cicada in a climate coal mine?
Brood X, the most numerous group of 17-year cicadas, could see its numbers winnowed down by climate change—not necessarily because they’ll die off, but because they might convert to shorter generation times of 13-years cicadas as warming soil temperatures shorten their life cycles, Raupp said. “Cicadas are kind of a model system for tracking issues of global change, and we’ll better understand how things like urbanization and climate change are affecting the distribution and abundance of all life on earth,” Raupp said. “This is a powerful data set that will be very useful.”

In a changed media market, cicadas were ready for their close-up
This year saw the emergence of a voracious appetite for information about cicadas, Raupp said. He believes it was driven by social media sharing—a dynamic that essentially didn’t exist in 2004—and reflected in a tsunami of traditional media coverage from TV, radio and newspapers from around the world (many of whose representatives showed up at his house in Columbia, Md.). “Sometimes we’d be running four or five film crews from around the world through my neighborhood and around my neighbors yards to get footage for documentaries,” he said. 

With the help of UMD students, people warmed up to cicadas
“I noticed a lot less, ‘OMG, it’s a plague … let’s get out of town!’ and a lot more ‘This is going to be cool!’ from the public this year,” Raupp said. He attributes that change in part to a concerted effort by the students and faculty of UMD’s own Cicada Crew to turn a strange and stunning natural spectacle into a perfect opportunity to teach accessible science.

“The students were just fantastic in this project, and had a chance to appear on “NOVA,” do interviews with Voice of America, do dozens of talks and learn the fundamentals of scientific outreach,” he said. “I think the Cicada Crew and enthusiastic journalists helped this turn out to be a very positive experience for tens of millions of people.”