By Bernheim
Rare Blue Ghost Fireflies Found at Bernheim Forest
Bernheim contributing to research on species
Fireflies, also often called lightning bugs, are one of the few groups of insects that are bioluminescent. That means they can produce light through chemical reactions within the organism. According to the Xerces Society, there are around 165 firefly species in the United States and Canada. Kentucky is home to more than 15 species.
At Bernheim Forest and Arboretum, volunteer naturalist Bill Napper has identified 13 species of fireflies, including the rare blue ghost (Phausis reticulata). Primarily found in the Appalachian Mountains, this rare species has been observed in several locations throughout Bernheim.
Active from May through June, blue ghost fireflies emit a distinctive dim, blue-green glow instead of the typical blinking pattern. Glowing, flightless females stay low on the forest floor, while the males fly above them in search of mates. Blue ghost males can glow for up to one minute.
Napper often leads night programs at Bernheim, including Firefly Fridays and Owl Prowls. On Tuesday, June 10, he took a small group out with the hope of witnessing blue ghosts.
During the excursion, Napper chatted about the many different fireflies he has witnessed at Bernheim. He explained that not all fireflies flash and that some fireflies don’t glow at all. All firefly larvae are bioluminescent, which distinguishes them from other beetles.
“I never knew there were so many different species of fireflies. It was truly a delight to witness the enchanting display of the blue ghost lighting up the forest,” stated Lynette Cox, marketing and communications director at Bernheim Forest and Arboretum. “It was a reminder to me of the wonders of nature and the importance of protecting it.”
The survival of fireflies is threatened by habitat loss, light pollution, pesticide use, poor water quality, and climate change.
“The blue ghost is especially sensitive to environmental threats. Artificial light can interfere with their ability to find mates and avoid predators. Habitat destruction and climate change are also serious concerns for their survival,” explained Kelly Vowels, research coordinator at Bernheim Forest and Arboretum.
Blue ghost females are wingless and rely on fallen leaves in the forest floor. Fallen leaves provide protection for both the female, eggs, and larvae. The forest floor also provides sustenance for firefly larvae as they often feed on worms, snails, and slugs.
Bernheim is working with the Stanger-Hall Lab at the University of Georgia to study the Ellycnia corrusca complex. The goal of the study is to clarify the evolutionary relationships between the Ellychnia and Phausis genera across North America. Bernheim is one of several sites contributing. Specimens of the blue ghost and other Phausis species are being collected for the study.
During the hike, Napper and Vowels collected three male blue ghosts to submit to the research project. The blue ghost firefly is small and comparable in size to a grain of rice. Genetic testing will be completed to help identify how the ones at Bernheim are related to other species across North America.
“With global firefly populations in decline, this research will help us better understand and protect these incredible insects. The more we know, the more we can do to ensure their survival,” added Vowels.
Discover More
The Fascinating World of Fireflies, published May 29, 2025
More Than a Glow: Fireflies as Pollinators, published June 19, 2025
