Your cicada questions, answered
Experts share all about cicadas—here’s what you need to know
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While there are magical myths and romantic legends surrounding the muse of a chorus of cicadas, most of us hear the tale of the 1-inch black bug with red eyes and an enviable wingspan and think, “Oh no, not again.”
Because they tend to overwhelm communities by covering the ground with their newly shed nymphal skin (and eventually their corpses) and filling the air with loud singing (up to 100 decibels, only 30 lower than a jackhammer), it’s no wonder cicadas typically elicit an unwelcome response.
On the heels of last year’s brood, we decided to bug Dr. Gene Kritsky, dean of the School of Behavioral and Natural Sciences at Cincinnati’s Mount St. Joseph University and the “Indiana Jones of Cicadas,” to understand this visitor a little better.
What is a cicada?
Cicadas are insects in the order Hemiptera, joining a few unsavory characters including stink bugs, bed bugs and aphids. North America is home to about 200 species of cicadas. While most emerge annually, seven of those are periodical, including four species of 13-year cicadas (translation: they emerge every 13 years) and three species of 17-year cicadas.
Within those species, there are three broods of 13-year cicadas and 12 of 17-year cicadas. For those not in the know, a brood is a regional, multi-species grouping of periodical cicadas that emerge on a common schedule.
The life cycle begins with eggs laid in the terminal ends of the tree's branches. After six to 10 weeks, nymphs hatch from those eggs, climb down and dig below the earth's surface to further develop. Once they’re ready (this time varies with species, but is from one to 17 years), mature insects climb out (aka emerge) from their underground nurseries and head for the trees.
While periodicals emerge in late April and early May through mid-June primarily on the East Coast but as far west as eastern Nebraska, Kansas and Arkansas, annuals are found throughout the whole country from June into September.
Timing and location aren’t the only differences between these cicada groups. Each has a different survival strategy. While annuals are cryptically colored in green and black to hide and survive in smaller numbers, periodicals’ motto is “go big or go home.”
During emergence years, like we experienced in 2021 with Brood X, millions come out for the ultimate display of safety in numbers. “Their survival strategy is to overwhelm their predators,” says Kritsky.
While predators like birds can see (and subsequently snack on) perhaps one cicada a day, there are still millions of cicadas left to reproduce.
What is the cicada life cycle?
Bad rap notwithstanding, Kritsky has built a career around the beauty of these misunderstood creatures.
“They're quite beneficial to the ecosystem,” explains the educator who has dedicated 46 years to periodical cicadas. Throughout the insect’s entire life cycle, nearby flora and fauna win.
“When the females lay their eggs, it’s almost like a natural pruning,” he says of this process that creates splits in the tree branches that will weaken them over time. In areas where Brood X was heavy last year, trees will enjoy a greater flower set and fruit yield this year.
The emergence stage also lends a helping hand to the surrounding forest. “When nymphs emerge from the ground, the holes they make act like a natural aeration for the soil,” he says, noting that part of the Midwest known for its high clay content that bakes solid in the summer benefits additionally from increased water access to tree roots.
Adult cicadas are also a food source for predators, even helping them to bounce back from unforeseen issues.
“Many years ago in Indiana, a lot of raptors had a disease that caused a decline in the population. The cicadas emerged [which led to] more mice, more voles, all sorts of wonderful things. And that provided a new food crop to allow more of the young [raptors] to survive. It helped the population recover.”
Broods also tend to fatten up an area’s wildlife. Kritsky tells of the Ohio Division of Wildlife’s discovery that turkey body weights taken during hunting season were found to be larger in areas after a cicada emergence.
The end of life for a cicada doesn’t mean their work here is done. Corpses that mostly collect at the base of trees also add a giant boost of natural fertilizer during brood years.
“As they decay, all those nutrients go back into a nutrient cache at the base of the tree,” he adds.
When do cicadas emerge?
Some periodicals don’t get the memo and arrive fashionably late to their own party. Under the general term “stragglers,” these tardy cicadas aren’t uncommon, according to Kritsky. Especially as weather patterns change.
“Periodical cicadas are insects of climate. They come up when soil temperatures reach 64 degrees Fahrenheit, and they’re attuned to the climate,” he explains.
As the weather shifts (for example, wetter springs, warmer winters), cicadas act accordingly by coming out earlier or later. “They're not doing anything unusual. They're doing what they're supposed to do. It's just that the climate is unusual.”
Keep tabs with a cicada tracker app
Want to get involved in tracking these gentle giants? Thanks to Kritsky, there’s a free app for that. The professor worked with the Center for IT Engagement at Mount St. Joseph to create Cicada Safari. Over 200,000 people have downloaded the interactive cicada tracking app that allows you to submit your photos. Don’t be afraid to get close while snapping—cicadas don’t bite or sting.
“We’ve never had that number of boots on the ground,” he says, adding there have been over a half-million verified reports, compared to the previous best map during a brood year of only 8,000.
While the next brood is expected in 2024 (when XIII and XIX emerge), anyone anywhere can snap and submit whenever they see a cicada. You might even be able to uncover the mystery of a brood of missing cicadas.
“There’s a now-extinct group called Brood XI,” he explains. “Back in 1699, 1716, and 1733, there was a massive emergence, and it continued up in good numbers up to 1869 and started dwindling at the beginning of the 20th century,” he explains.
The last Brood XI cicada ever reported was in 1937, but, thanks to Cicada Safari, a report last year from New England areas showed exciting potential Brood XI activity.
“It's important for people in Massachusetts, Rhode Island and parts of Connecticut to look for periodical cicadas over the next six weeks,” he explains. “There could be a little pocket left of what we thought was an extinct group.”
And that would be a discovery of which Indiana Jones would likely approve.
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