2   +   3   =  

This story is part of our series, Wild Pennsylvania. To check out all of the other stories in the series, click here

Fireflies can make a summer night seem magical.  But, these summer evenings, are you seeing less fireflies than you did when you were a kid? 

Julie Cecchini, a self-proclaimed lover of insects who has fond memories of catching fireflies as a child in her grandparents’ backyard, thinks so. 

“It feels that way, but I think I don’t go out and look for them like I did when I was a kid either,” she said. “I am wondering if it’s because of all the light in the world we have now and just some of the things that folks use on their yards and that.” 

LISTEN to the story

Trying to Understand Threats

Cecchini’s questions led her to sign up for a recent Firefly Watch training at Audubon Society of Western Pennsylvania’s Beechwood Farms Nature Reserve near Pittsburgh. Firefly Watch is a citizen science project that combines the quintessential summer ritual with scientific research. Researchers want to know what affects firefly populations. Why are there a lot in some areas and none in others?  But scientists can’t answer these questions until they have the data. 

Nature educator Scott Detweiler leads the Firefly Watch trainings at Beechwood. He explains that while a lot of significant firefly research exists, just simple counts of common fireflies weren’t happening. The Museum of Science in Boston started Firefly Watch in 2008 and Mass Audubon took over the project in Spring of 2018. All of the data is available on their website for anyone to explore.

“Hopefully they’ll have some better idea, as time goes on, if firefly numbers are truly declining,” Detweiler said. 

Visualization of reports submitted to Firefly Watch from citizen scientists. Credit: Matthew Smith and Mapbox volunteers Lo Benichou and Sam Fader.

What You’ll Learn at Firefly Watch Training

You don’t have to go to a training to become a volunteer for Firefly Watch. But if you do, you’ll learn a lot.

For starters, they aren’t bugs or flies. They are bioluminescent beetles that light up because of a chemical reaction in their abdomen. Each variety sends out its own distinct signal. 

Some do two flashes in a row and then wait four seconds. Another does a flash-flash-flash and then stops. The fireflies can tell one from the other by the pattern of the flash and the length of the flash. 

There are 3 common varieties in Pennsylvania. The one you see the most often is the Photinus pyralis, also known as the Big Dipper, because it makes a J-shaped swoop as it lights up.

Different types of fireflies become active at different times of night. Some fireflies begin flashing at dusk and blink for less than an hour.  Others start later and keep at it until midnight or so. Here in Western Pennsylvania, our earliest flashing fireflies (Pyractomena) start showing up in late May. Others appear in June and July. 

Fireflies use their bioluminescent signals to find and attract mates – kind of like a silent love song.  The male flashes and the female, most often on a tall blade of grass, sends a signal back saying, “Yeah you seem good. Come introduce yourself.”

Fireflies also produce a chemical that makes them unappetizing to other creatures. In fact, fireflies are predators. 

Each type of firefly sends out its own distinct signal. Credit: Mass Audubon

Counting Protocol

The protocol for counting fireflies is simple.  All you need is a stopwatch, and a couple of minutes once a week to do some counting.

“You just pick your spot,” he explained to the trainees. “And just within your field of vision, how many do you see? You have a 10 second count and that is all there is to it.”

As the group stares into the same patch of darkness to observe, they’re not counting specific fireflies – just how many flashes they see in the 10 seconds. And it’s a range, not a specific number: 0; 1 to 5; 6 to 10; 11 to 25; more than 25. 

At home, volunteers make three 10-second observations within a few minutes and then record the numbers on a form, along with a few data points like weather conditions, habitat type and if any artificial light is around.

The whole thing takes 5 minutes, max. Whenever it’s convenient, participants upload their data to a website maintained by Mass Audubon. It gets passed on to firefly researchers who are trying to learn more about the geographic distribution of fireflies, and which environmental factors impact their numbers.

Love Fireflies? Here’s How to Safely Catch Them

Mia Haber came to the training with her husband, Sean Guillory and their 8-year-old daughter, Zoia. They’ve been counting from their back porch on Sunday nights ever since. Haber is from Israel, and said for her, just seeing fireflies feels like a novelty. 

“I didn’t even know they existed until I came to the U.S.,” she said. “Like, I have never seen them before.”

And Detweiler said, if you like fireflies, you can do some things to encourage them to come to your yard: Plant grasses and shrubs of varying heights; don’t use pesticides; and turn off the porch light. 

“When there is a lot of artificial light, it’s harder for them to see each other’s signals,” Detweiler explains. “And it’s harder for them to find mates.”

Fireflies continue lighting up the night sky through the end of the summer. So there’s still plenty of time to volunteer with Firefly Watch. 

The Audubon Society of Western PA is sponsoring an event called Firefly Family Fun at their Buffalo Creek Nature Center, July 19th. There will be  a short presentation and book on fireflies, and then they’ll go outside observing and counting them as night falls. A campfire and s’mores follows. Tickets and more info HERE.