Researchers: Fireflies are being threatened by artificial light, habitat loss

Growing up around Seattle, Ainsley Seago said she never saw a firefly until she visited Hershey as a teenager.

These days, she watches in amusement as her 10-year-old son, Maxwell, enjoys catching lightning bugs and releasing them.

“How can you not catch them?” asked Seago, associate curator of invertebrate zoology at the Carnegie Museum of Natural History. “They are magical and look like supernatural glowing creatures that fly.”

What looks like a wonderland of tiny, flashing lights are mating signals for lightning bugs. Increasingly, those signals are being interfered with by outside sources, which is causing a decline in firefly populations worldwide, according to scientists.

As many as 1 in 3 firefly species is at risk of extinction, according to a study performed by researchers from the Xerces Society, the ABQ BioPark and the IUCN Firefly Specialist Group.


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The direst threats to fireflies are habitat loss, overuse of pesticides and light pollution, said Sara Lewis, one of the study’s authors and a professor of biology at Tufts University.

Artificial light at night interferes with courtship rituals of flashing fireflies and glow-worm fireflies, said Lewis, author of “Silent Sparks: The Wondrous World of Fireflies.”

“Males flash less, and females stop responding to males’ courtship signals,” she said. “The upshot is lower mating success, fewer eggs laid to launch the next firefly generation.”

Turning off or shielding artificial lighting turns up the romance for fireflies as they can better see each others’ signals.

“We’re lucky that light pollution is instantly reversible – just flip the switch,” Lewis said.

Firefly populations are also impacted by sterile, closely cropped lawns without tall stalks of grass for female fireflies to sit on as they watch a potential mate signaling, Seago said.

And pesticides used on farm fields can cause fireflies to behave abnormally, making them less likely to survive and mate, she said.

Firefly festival

Pennsylvania Firefly Festival Inc. is holding a “Lights Out for Lightning Bugs” campaign this month to encourage people to be mindful of lightning bugs.

The “Lights Out” campaign officially runs from June 9 through June 25, but the nonprofit organization from Kellettville in Allegheny National Forest suggests residents dim their outside lights and opt for motion-activated lights throughout the summer, which can help fireflies mate and reproduce.

The sold-out 10th annual Firefly Festival runs two nights, June 24 and 25. The event is limited to 50 people each night so as not to disturb the fireflies or possibly trample them and their habitat, said Peggy Butler, who founded the Firefly Festival organization with her husband, Ken.

Synchronous fireflies – lightning bugs that flash in harmony – were discovered in Kellettville in 2011, and people wanted to see them, Butler said.

The couple would host firefly watch events as a promotion at their Forest County bed and breakfast, and it became so popular that they officially launched the annual event.

“It looks like a light show, with a strobe-light effect much like a marquee in a theater with the lights flashing together,” Peggy Butler said. There can be hundreds of fireflies viewed from one spot, she said.

These days, biology students and researchers from universities visit and conduct research around the Butler home.

In 2019, Tufts University researcher Avalon Owens conducted a study in Kellettville that found light of any color essentially shuts down the flashing replies of females to attract a mate.

Firefly tourism

Because of lightning bug decline, people are heading to the forests and the deep country to find firefly activity reminiscent of their youth.

Firefly tourism is taking off, with events offered by parks and organizations, including recent outings in Ohiopyle and Butler County, Butler said.

Parks, conservation areas, forests and even railroad rights-of-way and cemeteries are important as sanctuaries for fireflies, said Lynn Faust, author of “Fireflies, Glow-worms and Lightning Bugs.”

“Pennsylvania has great firefly diversity with many showy species,” she said.

Butler said she hopes interest in viewing events will grow.

The Firefly Festival is quite the spectacle, she said.

“Once it got out into the community of ‘firefly people,’ they wanted to add it to their bucket list,” Butler said.

Mary Ann Thomas is a Tribune-Review staff writer. You can contact Mary at 724-226-4691, mthomas@triblive.com or via Twitter .

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