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The Colorado June air was thick with summer heat. Mosquitoes rose in clouds around us, testing our resolve while we gathered our cameras and sensors. We walked into the wetland, down the unmarked path until the cattails rose shoulder-high. The sounds of frogs and crickets filled the air as we set up our cameras and waited. Then we spotted them: tiny lights lifting from the grasses, blinking in slow rhythms.

Bioluminescent beetles, commonly known as , are widespread throughout the Eastern United States but .

Even though many are stargazers and hikers, most Colorado residents don't know that fireflies share their state.

We are and a who are working to shed light on Colorado's hidden fireflies.

In the past few years, we have observed and filmed elusive bioluminescent fireflies all over Colorado, racing each summer against their brief and unpredictable flashing season.

Last year, in early June, it was too early, we thought, for fireflies in Colorado. For weeks we had been checking weather forecasts, comparing them to previous years, waiting for warmer nights and rising temperatures—the signs that would tell us it's firefly time.

Then we got a tip. A friend mentioned seeing one or two flashes near their property. The next morning, we packed our gear, rearranged our schedules and contacted our volunteer network. The field season began in a literal flash.

As adults, fireflies live and flash for only about —and even then, just for a few hours each night. It's easy to blink and miss the entire season. The next generation , though development may take up to two years in arid climates. Making the most of that narrow window is one of the many reasons we rely on volunteers who help us spot the first flashes and record observations across Colorado.

Western fireflies face unique environmental challenges

Our work joins a growing chorus of scientific observation , which pop up across the arid landscape near temporary wetlands, marshes, drainages, desert rivers and other water sources. Because of the dry landscape, these populations tend to be fragmented, isolated to where the water is and nowhere in between.

This strong tie to small, unstable habitat spells vulnerability for the fireflies. If the water runs out, or their habitats are damaged by water or light pollution, the flashing populations could vanish. Pesticides in water are , and artificial light , preventing successful reproduction. Many populations and species of fireflies are due to these factors.

Organizations such as at the University of Colorado and the are studying the . Many of the species are either endangered or not yet described.

The fireflies of the along the Front Range, for example, still do not have a species name and from other Photuris around the country. Preliminary genetic results suggest at least one new species might be found here. The genetic data also suggests at least five different bioluminescent species of fireflies are present in Colorado.

How flash patterns help fireflies (and us) tell species apart

During their short mating season, .

Males produce a series of flash-on, flash-off events, each with specific durations and pauses. These Morse code-like signals communicate what type and how fit the fireflies are to potential mates in the darkness.

When females detect a suitable male, they respond with their own unique flash pattern.

Our work piggybacks on this evolutionary adaptation. We first recorded populations using two video cameras, which allowed us to accurately track individual fireflies in three dimensions and separate their flash patterns.

We used the data on the flash behavior from different species to train a neural network that can . Our algorithm learns the unique flash patterns from our data and can identify the species of firefly that is present in a video.

This is a powerful tool for firefly conservation efforts. The camera footage can cover more time and ground than field surveys conducted by humans, and our algorithm can more quickly identify species that might be threatened.

Fostering community engagement with citizen science

Based on our success with community science data collection across , including Tennessee, South Carolina and Massachusetts, we wanted to apply the same principles to Colorado's firefly populations. This is a big undertaking: There are dozens of fragmented sites where fireflies are active across Colorado, and more are reported by volunteers every season. Our team of two cannot visit and survey every site during the short firefly season.

In 2023 we put out our first . Since that time, 18 community members in Boulder, Fort Collins, Divide and Loveland joined the filming effort. We provide cameras for the volunteers, who bring them to their nearby wetlands and set them up in the fading light.

Last summer, we partnered with local land management agencies in Boulder, Fort Collins and Loveland to host , where we spoke about firefly biology and conservation to audiences of all ages. On many of those nights, as the flashes began, we heard the excitement build: quiet gasps, hushed enthusiasm and a whisper such as, "Look at that beautiful streak of light!"

Fireflies have an important story to tell, and here in Colorado that story is just beginning. Their brief flashes each summer help us learn about communication, ecology and how these delicate insects respond to an ever-changing world.

If you'd like to help us find and study fireflies in Colorado, you can .

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