Fleeting fireflies illuminate Colorado summer nights − and researchers are watching
- Researchers are studying fireflies in Colorado to shed light on their elusive behavior and conservation status.
- Fireflies are scarce west of Kansas, but can be found in Colorado’s wetlands and temporary water sources, where they face unique environmental challenges such as dry landscapes and pesticide toxicity.
- A team of researchers is using camera footage and machine learning algorithms to classify firefly species based on their flash patterns, which helps identify potential threats to conservation efforts.
- The project aims to engage the community in citizen science by recruiting volunteers to film and record fireflies in Colorado’s fragmented habitats, providing valuable data for conservation efforts.
- By studying fireflies, researchers hope to learn about communication, ecology, and how these delicate insects respond to an ever-changing world, with the ultimate goal of protecting their populations and species from extinction.
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 lampyrid beetles, commonly known as fireflies or lightning bugs, are widespread throughout the Eastern United States but far more scarce west of Kansas.
Even though many are stargazers and hikers, most Colorado residents don’t know that fireflies share their state.
We are an associate professor of computer science and a Ph.D. candidate 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.
Nolan R. Bonnie and Mac Stone
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 two weeks a year − and even then, just for a few hours each night. It’s easy to blink and miss the entire season. The next generation overwinters underground as larvae, emerging as adults the following year, 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 focused on western fireflies, 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 toxic to firefly larvae and their prey, and artificial light inhibits the flash courtship between males and females, preventing successful reproduction. Many populations and species of fireflies are threatened with extinction in the United States due to these factors.
Organizations such as our lab at the University of Colorado and the Xerces Society for Inverteberate Conservation are studying the distribution of and direct threats to western firefly populations. Many of the species are either endangered or not yet described.
The fireflies of the Photuris genus along the Front Range, for example, still do not have a species name and appear to be genetically distinct 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, fireflies use their flash patterns as mating calls.
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 from around the U.S. 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 classify the firefly’s flash pattern with a high degree of accuracy. 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 other states, 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 call for volunteers in Colorado. 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 informative community events, 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 sign up to join our community science project.
Orit Peleg receives funding from the City of Boulder Open Space and Mountain Parks, CU Boulder's Timmerhaus Fund Ambassadors, National Geographic Society, and Research Cooperation for Science Advancement.
Owen Martin receives funding from Boulder Open Space and Mountain Parks (OSMP).