1st Cicadas Have Emerged In PA, Billions More Expected Soon

PENNSYLVANIA — Waves of "Brood X" cicadas are set to emerge this spring after 17 years underground, and they're expected to arrive earlier than their parents.

Temperatures may play a big role in why the bugs are emerging earlier in Pennsylvania, according to a new study. Climate Central, an independent organization of scientists and journalists, says that the earlier emergence is due to warmer temperatures (learn more about the study and its methodology here).

In the Philadelphia area, cicadas are emerging up to 22 days earlier than they did in 1970. That number sits at 15 days in Pittsburgh, and 11 days in Allentown, according to the study.

Some bugs have already begun to emerge from the ground. Cicada Safari, an app built by scientists at Mount St. Joseph University in Cincinnati to watch the emergence of the Brood X cicadas, records sightings as they happen with photos submitted by users.

There have been sightings reported in recent days near Schwenksville and Harleysville in Montgomery County, as well as smatterings in places in Lehigh County and Cumberland County, the app showed on Friday.

“Because ground temperature provides an important cue for cicadas' emergence, and spring temperatures have trended higher since the great-great-grandparents of this year’s Brood X cicadas emerged in 1970, that cue is likely to arrive sooner,” researchers said.

According to Climate Central:

“Cicadas typically emerge in force when ground temperatures reach approximately 64°F degrees, often after a steady rain. Some places with Brood X cicada concentrations have already reached that temperature threshold. The 10-day average temperature across the Brood X region is running 8 degrees Fahrenheit warmer than at this time in 1970, and 1.1 degrees Fahrenheit warmer than in 2004.”

The synchronized emergence of Magicicada cassinii, as this cicada brood is scientifically known, is a true marvel of nature. The species' extraordinarily long life cycle — the longest of any insect on the planet — is part of an evolutionary strategy that has allowed the cicada to survive for 1.8 million years, or from the Pleistocene Epoch, according to a CBS News report.

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

The cicadas spend more than a decade underground feeding on tree roots before their synchronized emergence as young adults. The males sing with urgency, trying to mate before they die just three or four weeks later.

Experts say that Brood X, or Great Eastern Brood cicadas, are expected to number in the billions throughout the region.

The cicadas are completely harmless to humans, but can produce quite a loud sound once they start singing.

See localized data here.

With reporting from Patch correspondents Eric Kiefer and Anna Quinn