Photograph courtesy Gene Kritsky
Following a career spent studying the behavior and biology of periodical cicadas, Gene Kritsky, Ph.D.—professor emeritus of biology at Mount St. Joseph University and chief science officer for the Center of IT Engagement—created a better way to map brood emergences across the country. Cicada Safari, a free app available across platforms, allows users to take photos and videos of cicadas they discover to be added to a live map. Kritsky discusses how this app came to fruition, what users can learn from mapping cicada emergences, and where to expect this year’s Brood XIV emergence, starting in mid-May.
Let’s start off broad. Why cicadas?
I am a frustrated historian, and cicadas are bugs of history. The first [historically recorded] emergence of periodical cicadas was in 1634 in Plymouth Colony…I originally wanted to go to college [for] human paleontology. In the process of talking with my professor…he said to take an entomology class. So I went to enroll for classes for the next fall. It was taught by Frank Young, the periodical cicada specialist in Indiana, and in the second week, he starts talking about these bugs, and I changed my major.
Where did you get the idea of mapping cicadas through an app?
Crowdsourcing with periodical cicadas started in the 1840s.… When I did my first project on periodical cicadas, I drove all over the area where I thought the cicadas emerged. In 1987, I started a cicada hotline. I got so many calls that it broke my answering machine. Fast forward to 2004, and I asked for e-mails. I was getting an e-mail a minute about people telling me where cicadas were. Finally, Steve Jobs came up with [smartphones] and I thought, there’s some potential here, especially when they added the camera and location services. I mentioned this to our new provost for technology, and he came to me late 2017 about doing this app. I met with students and we got it ready for the emergence in spring 2019. We got 5,000-plus responses.
What did you learn about cicada behavior by mapping them?
2020 was the big one that was tested. Brood IX was a small brood in West Virginia, western Virginia, northeastern and northwestern North Carolina, and we were getting reports, and drove to see if they were there. What happened was something totally unknown. That brood is east of the Mississippi, so it went from eastern Missouri, eastward. We got 9,000 records of Brood IX, but we got hundreds of records from places where cicadas weren’t supposed to emerge. In the past, researchers like me would go where we knew [cicadas] were, and we’d drive around the boundary line to see what their extent was. We never thought about looking 500 miles away. In addition to Brood IX emerging, four other broods emerged. In Chicago, Brood XIII emerged four years early in massive numbers, and that was a real surprise. We also had some four-year-late Brood X’s here in eastern Ohio, about 5,060 reports. We had thousands of records in Chicago of Brood XIII, emerged four years early. That’s a common phenomenon we now know about in cicadas. We had some four-year late emergences from Brood V in eastern Ohio, and then four-year-early emergences of Brood XIX, of 13-year cicadas coming out after nine years. Cicada Safari was helping us map cicadas where we never thought of looking for them before. That was a big deal. The next year was Brood X, and we had over 200,000 downloads. We received over half a million photos. That was the largest survey ever done of periodical cicadas.
Why are cicadas emergence patterns changing?
Periodical cicadas are an amazing animal. Not only are they a bug of history, but are one of the most useful model organisms in the insect world, helping us understand things like impact of climate, impact of deforestation, its role in ecosystems, and so on. It’s a really good animal to study some fundamental questions about biology.… With Cicada Safari, we’ve been able to document how a cicada brood can spin another brood to come out. One of the things I’ve documented is off-cycle emergences. When cicadas come out early or late, they often come out four years early or four years late…all the broods evolved as the ice sheet retreated after the last ice age, the cicadas spread northward, and they are doing so based on the weather changes, some of them are coming up in these four-year-off cycles. What would cause this? It’s changing temperatures in the last 25 years because of global warming. We have had four-year accelerations now of Brood II, V, X, XIII, and XIX. Why is that happening so often now? Periodical cicadas emerge from the ground when the soil temperature reaches 64 to 65 degrees Fahrenheit. That’s now two and a half weeks earlier than it was a century ago.
What else can we learn about cicadas?
We get the question, “What good are cicadas?” When the immature [cicadas] come out of the holes in the ground, those holes persist in the soil because we have such a high clay content. Those holes will persist to December and January, but especially during the summer months, when it’s really hot and dry, the ground gets really hard. It’s a natural aeration and irrigation—when it does rain, a lot of it goes down those holes and helps water the trees. When they start climbing out as adults, after they have fully formed, they climb up the tree and sit there for five more days, continuing their maturation. Then they start singing. Once they are singing, they are food for all sorts of predators, and this increased nutrition allows for predators to give birth to more offspring. We know that during turkey season, that male turkeys have a higher body weight in areas where the cicadas emerged than areas where they didn’t. Third, when a female lays her eggs, she lays it on the terminal end of branches that sometimes break and turn brown, that’s called flagging, it’s a natural pruning. Lastly, they die after mating, and they collect at the base of trees. As they decay, their nutrients go into the soil around the tree where they lay their eggs, and they create a nutrient cache to help sustain the tree for the next 17 years.
What can we expect from this year’s emergence?
It’s going to be primarily on the east side of Cincinnati. You’ll see some reasonable numbers in the Madeira area, Kenwood area—that area is slowly transitioning to become Brood X. Areas like Milford, Batavia, and across the eastern area [of Cincinnati] and parts of northern Kentucky will have reasonably good numbers.
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