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Banner image: Fireflies dance over a field near Sawhill Ponds in Boulder, Colorado. (Credit: Peleg Lab)

Owen Martin steps carefully through the knee-high grass growing up around a long-abandoned railroad track near Sawhill Ponds in Boulder, Colorado. It’s almost pitch black out. The sun set 45 minutes ago, and the only light now comes from the distant buzz of cars on Valmont Road.

Or almost the only light. If you let your eyes adjust to the dark, you can just make out the twinkle from hundreds of faint specks. They flash on and off as if someone spilled yellow-green glitter across this empty field. 

Martin, a doctoral student in computer science at CU Boulder, is hunting for fireflies.

“There’s one right there,” he says, holding up a butterfly net. “It’s leading me on a little chase.”

Many people who call Colorado home might be surprised to learn that fireflies (or lightning bugs, depending on who you ask) also live in the state. But, if you’re lucky, you might stumble on a few pockets of these insects lighting up the night. You just need to know when and where to look.

That’s what Martin and his advisor Orit Peleg are trying to figure out now. In a project that blends technology with natural history, researchers in Peleg’s lab have spent summers since 2018 traveling across the state in search of fireflies. They use to learn more about the insects, including the patterns they make with their flashes. In many ways, the team is in a race against time. In Colorado, as in other places around the world, firefly populations may be vanishing as a result of humans paving over wetland habitats and saturating the night sky with artificial light.

“Firefly flashes are like a little, secret language,” said Peleg, associate professor in the BioFrontiers Institute and Department of Computer Science. “They are very special, and we have a lot to learn from them.”

Introducing Colorado fireflies

It’s a new experience for Martin. The researcher grew up not far from this natural area in Louisville, Colorado, but had never seen a firefly at home until three years ago. He said that observing these animals in the wild is a “wonderous feeling.”

“It’s all dark, and you feel like the rest of the world isn’t there anymore,” he said. “You feel like you are floating in space, and there are all these stars moving around you.”

At Sawhill Ponds, he’s trapped one of those stars now. He gingerly moves the insect from his canvas net to a covered petri dish. The firefly is about a half-inch long, and you can just make out its orangish head and black wings. A light organ on the bug’s abdomen glows, flashing like the beacon from a lighthouse. 

Fireflies belong to a family of beetles known as Lampyridae, and roughly 2,000 species of fireflies can be found across the globe. It’s not clear how many live in Colorado. The insects near Sawhill Ponds belong to a common genus called Photuris. The name roughly translates to “light terror” because female Photuris fireflies sometimes use flashes to lure in, then devour males from different species. 

A male Photuris firefly coated in pollen sits on a thistle plant near the Boulder Reservoir. (Credit: Owen Martin)

Owen Martin uses a red light to examine a firefly in the field. (Credit: Owen Martin)

Entomology collections at the CU Museum of Natural History include specimens from Photuris and four other genera found in 19 Colorado counties—ranging from Yuma County in the northeast to Montezuma in the southwest. Martin himself has observed fireflies in the town of Divide, which sits near Pikes Peak at an altitude of more than 9,000 feet.

Still, there are good reasons why these luminous animals remain such a mystery in the state. Unlike fireflies in the eastern U.S., which can abound all summer long, Colorado fireflies tend to cluster in swampy areas and are active for just a few weeks per year—appearing in the second half of June, then disappearing again by mid-July. Martin's research is supported through the President's Teaching Scholars Program and Timmerhaus Fund Ambassadors at the University of Colorado and by the City of Boulder Open Space and Mountain Parks.

“A lot of people here come from places like the Midwest where they’ve seen fireflies. But they don’t know about them in their own backyards,” said Martin, who wants to raise “firefly literacy” in the Front Range.

Speaking firefly

Part of that goal hinges on understanding their secret language, Peleg said.

She explained that male fireflies flash to attract females, which often remain hidden on the ground. Each firefly species, however, has its own, unique flash pattern. 

“It’s like Morse code,” she said. “It’s this simple light on, light off signal, and that’s probably as close as it gets to computer language, ones and zeros, in the animal kingdom.”

To explore those patterns, her team uses 360-degree GoPro cameras to record fireflies in the wild. They then feed those recordings into computer programs that analyze the patterns. In recent research, for example, the group dug into the flashing behavior of fireflies in the Great Smoky Mountains of Tennessee—where thousands of insects synchronize their displays so that they all flash in unison, bathing entire hillsides in light.

Peleg’s team by observing how their neighbors are flashing, then adjusting their behavior to match.

Martin is gathering similar insights into Colorado’s fireflies. Eventually, he and Peleg want to build a library of firefly flash patterns—a sort of Google Translate for insects. That way, people could record video of fireflies flashing, then automatically identify what species they’re looking at.

Protecting diversity

The researchers hope they can collect their data before it’s too late.

Across the globe, research on fireflies remains scarce. But a growing number of hints suggests that some species may be disappearing. 

In Colorado, artificial light is a major threat. Studies of fireflies from the eastern United States show that streetlights and other nighttime illumination can wash out the signals that fireflies are trying to communicate. It’s a bit like trying to carry on a conversation in the middle of a crowded bar. (Such “light pollution” can also make it more difficult to see the stars from Colorado). 

But there are a number of actions people can take to protect vulnerable firefly habitats. Martin and Peleg invite curious Coloradans to . A team at the Butterfly Pavillion near Denver is also , which could one day be released into the wild. 

The potential of those actions is on display at Sawhill Ponds. There, a strange light has caught Martin’s attention. It’s a firefly, but one with an oddly orange-colored light.

After a few swipes of his net, the scientist captures the mysterious insect. It’s noticeably smaller than the Photuris bug he caught earlier. It’s a Pyractomena, a completely different firefly genus and one Martin has not recorded at this spot before.

“This could be very exciting,” he says.

The new insect is a reminder that scientists still have a lot to learn about fireflies in Colorado. Martin encourages everyone to get out and look.

“Turn your lights off,” he said. “Then, between the middle of June and the middle of July, try to take some walks at night in your local wetland areas and see if you can find some.”