Brood X Cicadas: How To Track The Emergence In PA

PENNSYLVANIA — Residents in several Pennsylvania counties have a chance to be a part of an ecological phenomenon that only occurs once every 17 years.

An unprecedented citizen science effort has launched nationwide, as parts of 15 states will see billions of Brood X 17-year cicadas emerge in May or June. The public is invited to help scholars track and better understand this extraordinary natural display.

In Pennsylvania, impacted counties include Adams, Bedford, Berks, Bucks, Chester, Columbia, County, Cumberland, Dauphin, Franklin, Fulton, Huntingdon, Lancaster, Lehigh, Luzerne, Lycoming, Mercer, Montgomery, Northampton, Perry, Schuylkill, Somerset, and York

Cicadas are expected to emerge in the state in late May or early June.

RELATED: Billions of 17-Year Cicadas Will Emerge In PA In 2021

Anyone with a smartphone can download the free Cicada Safari app to help with the data collection on the emergence Brood X — or Great Eastern Brood, as this population also is known. It’s just a matter of snapping a photo or short video and uploading it. The app automatically captures the time, date and geographical coordinates. Once the images are verified, the information is mapped.

Parts of Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Michigan, North Carolina, New Jersey, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia and the District of Columbia will also see the emergence of Brood X.

In Pennsylvania, the following specific communities are expected to be hotspots, researchers say:

• Archbald, Artemas, Bedford, Carroll Valley, Coopersburg, Dinosaur Rock, Downingtown, Gettysburg, Green Lane, Kintnersville, Lake Nockamixon, Lancaster, Lititz, Malvern, Mertztown, Mohnton, Mt Gretna, Oaks, Oley, Perkasie, Perkiomenville, Phoenixville, Pittston, Quakertown, Red Lion, Roaring Spring, Solebury, Spring Mount, Stewartstown, Topton, Upper Black Eddy, and Warwick Park.

The Cicada Safari app was developed by Gene Kritsky, the dean of Behavioral and Natural Sciences at Mount St. Joseph University in Cincinnati and the author of “Periodical Cicadas: The Brood X Edition.” The app is available for both iOS and Android operating systems.

Kritsky told Entomology Today he hopes to get 50,000 observations from the citizen cicada scientists to help scientists understand more about Brood X, the largest cohort of cicadas that spend 17 years underground before emerging almost simultaneously to molt and mate.

Here are more 17-year periodical cicada stories you might enjoy:

• Billions, Yes Billions, Of 17-Year Cicadas Will Emerge In 2021
• Billions Of 17-Year Cicadas Emerging This Spring Are Edible
• For Copperheads, 17-Year Periodical Cicadas Are Fast-Food Buffet

The app was used last year to document Brood IX of the 17-year cicadas — an effort that was set back by the coronavirus pandemic — and also the emergence of four other off-year broods. Documenting the off-cycle emergences would have been more difficult without the app, according to Kritsky.

Scientists have long relied on local reports from everyday folks to help map periodical cicadas.

As early as the 1840s, when periodical cicadas were more of a mystery than they are today, researcher Gideon B. Smith “wrote newspaper articles asking readers to send him details of where they saw cicadas,” Kritsky told Entomology Today. “By the time of his death in 1867, he had documented all known broods of cicadas.”

And make no mistake: Periodical cicadas remain somewhat of an evolutionary puzzle. They spend more than a decade underground feeding on tree roots before their synchronized emergence as young adults. The males sing, raising quite a ruckus with their mating call. There’s some urgency to it: The males live three, maybe four, weeks after mating.

The females don’t sing but wait quietly to do their job perpetuating the species — to lay as many eggs as possible, up to 600 — before they die. They split the bark on living tree trunks, branches and twigs, burrow in, and lay between 24 and 48 eggs at a time.

According to one theory, cicada life cycles are prime numbers — that is, numbers that can only be divided by 1 or by themselves — as part of an evolutionary strategy that tricks predators.

University of Indiana biologist Keith Clay said in an interview with the American Association for the Advancement of Science that periodical cicadas are easy to catch and eat. For example, copperheads treat cicadas like fast food — they’re abundant and easy to obtain — and plenty do get eaten by these and similarly opportunistic predators, but enough survive to keep the species going.

“The main hypothesis is that it’s very difficult for predators to have a similar life cycle, where they could actually specialize on these cicadas 'cause they also would have to have a 17-year life cycle,” he said. “If cicadas came out every 16 years, for example, predators with two-, four, and eight-year life cycles would be around that year to eat them.”

Another hypothesis about the synchronized emergence of periodical cicadas is that the forced developmental delay was an adaptation to climate cooling during the ice ages.

Kritsky, who developed the cicada app, said this year’s emergence could give him and his colleagues a level of detail that hasn’t been seen before in centuries of research about these insects with long life cycles.

“I have been mining historical emergence records for 45 years, and in the process we have discovered new populations of broods that had been missed for over a century,” Kritsky told Entomology Today. “It’s amazing that an insect that has been studied for so long and by so many still has secrets to reveal.”