Do you remember chasing fireflies as a kid? Running around outside at dusk marveling at the twinkling lights is a common experience. Perhaps you even caught fireflies and put them in a jar to form a homemade lantern.

Although you probably didn’t realize it at the time, every firefly species has its own unique flash. Not only does the color vary from yellow to green, with one species even glowing blue, but the pattern differs as well. The common eastern firefly, which is the species you are most likely to see on summer nights in Delaware, makes a J-shape with its flash, which goes dark after a beat before lighting up again in about six seconds.

This unique flash enables fireflies to find other members of their species to mate with. While you might be inclined to think a firefly is just a firefly, there are actually more than 2,400 different species worldwide. That’s a lot of flash colors and patterns!

And of all these, few have a more striking flash than the Bethany Beach firefly, or Photuris bethaniensis. This extremely rare species is only found in a specific section of the mid-Atlantic, primarily the Delmarva Peninsula.

As the name implies, the Bethany Beach firefly was discovered along the Atlantic coast in southern Delaware. After being identified in the mid-20th century by a DuPont chemist with a passion for fireflies, the species then seemed to disappear for several decades before being detected again in 1998.

In 2019, the Delaware Department of Natural Resources and Environmental Control began a comprehensive survey effort that continues to this day. For seven years running, Jason Davis, a wildlife biologist in the DNREC Division of Fish and Wildlife, has ventured out near the Delaware beaches on summer nights to investigate potential habitats.

The Bethany Beach firefly relies on freshwater interdunal swales — basically wet, grassy areas between sand dunes. The species makes its home in these miniature valleys, where members live as larvae for two years before eventually pupating, taking flight and (hopefully) reproducing. After the mating season is over, the adults die off.

In a sense, their story can be considered a tragic tale — so much energy is spent waiting for a period of about six weeks when a firefly will have the chance to pass on its genes. Such is the circle of life.

The Bethany Beach firefly becomes active from late June to early August. That’s when Davis will perform his survey work, visiting as many as 100 different swales along the coast in Sussex County. He is generally able to knock out a few each night, using the opportunity to gather data so we can learn more about the species and how it’s trending.

Members of the species typically begin flashing about 35 minutes after sunset, so he’ll arrive before the sun goes down, gather his equipment and wait.

Wearing waders, a mosquito net and a headlamp, Davis will either walk out into the middle of a swale or, if the Bethany Beach firefly is present in sufficient numbers at that site, simply stand near the edge of the marshy area. He watches the flashes, keeping an eye out for the double green — blink blink, followed by about 3.5 seconds of darkness before the pattern repeats itself.

Despite the Bethany Beach firefly’s distinctive pattern and vibrant green color, identifying the species takes expertise, as several similar fireflies can often be found alongside it.

The flashing we see from lightning bugs flying around typically comes from males, while females remain on the ground. When they spot a flash from a member of their species, females will signal back, prompting males to close in in hopes of spreading their genes.

Still, not all is as it seems. Some females of the Photuris genus, which the Bethany Beach firefly belongs to, mimic other species’ flashes to lure in males, which they then eat. It’s for this seductive but deadly trait that members of Photuris are sometimes referred to as femme fatales.

Ultimately, there’s still much we don’t know about lightning bugs, especially rare ones like the Bethany Beach firefly.

But scientists like Davis are helping shine some light on the mystery. As he performs his work, Davis takes a rough count of the Bethany Beach fireflies he sees at a given swale and then, using a bug net, captures one. He’ll carefully transfer it to a small sandwich bag to make it easier to examine, a task for which his trusty light-up magnifying glass is invaluable.

Davis carefully looks over each insect he catches to determine if it is indeed a Bethany Beach firefly, making note of the pattern on the elytra (forewings) and pronotum (foremost thorax segment). He measures it — at 9 mm to 10.75 mm, the species is on the smaller side — and records the size as well as other information like weather condition, temperature, date and location on a sheet of paper that will be transferred to a master spreadsheet later. Before finishing, Davis takes pictures of the insect for the record.

Once that’s done, he’ll free the firefly, leaving it unharmed and armed with a story that would surely dazzle potential mates.

His work has helped determine the Bethany Beach firefly’s range is broader than previously thought. Not only has the firefly been identified from Lewes down to Fenwick Island, but in 2020, a DNREC botanist noted the type of swale the species relies on can be found at Assateague Island in Maryland. That led to Davis, working with biologists from the Maryland Department of Natural Resources and U.S. Fish and Wildlife Service, discovering the firefly outside Delaware.

A year later, staff from the Virginia Department of Conservation and Recreation spotted the species farther down the Delmarva Peninsula and even across the mouth of the Chesapeake Bay in mainland Virginia near the North Carolina state line.

Unfortunately, the Bethany Beach firefly faces real challenges from human activity. Climate change threatens the freshwater swales it needs to survive and perpetuate its species, while development risks destroying these habitats all together. Even if the swales are left untouched by residents and vacationers seeking to build their dream beach houses, increasing light pollution makes it harder and harder for males and females to find each other. And, pesticides and invasive species pose problems of their own for the little insect.

Members of the species are not thought to venture far beyond where they are born, and the loss of some swales to development makes it harder for the firefly to expand its range by “jumping” from habitat to habitat.

All that is why the species is one of 89, including 31 insects, considered endangered by the state of Delaware. It is the sole firefly on the list.

What’s more, in 2024, the U.S. Fish and Wildlife Service proposed to list the Bethany Beach firefly as federally threatened under the Endangered Species Act, making it the first type of firefly to receive such a distinction. The service continues to work on completing the final determination.

To some, this may seem pointless. After all, there are thousands of firefly species around the globe, including roughly 30 in Delaware alone.

But as Davis knows well, lightning bugs are charismatic, meaning they appeal to many people.

“Most people can say when they were a kid they chased fireflies. You don’t have any good memories of cockroaches or ants or something like that, so it has that warm feel to it,” he said with a chuckle.

What’s more, the Bethany Beach firefly is a part of the ecosystem, and you never know how removing even one small link can disrupt the entire web.

“Everything is connected,” Davis said. “If we lose that, what else would we potentially lose?”

Related Topics:  animals, coast, endangered species, firefly, fish and wildlife, fun, nature, outdoor delaware, sussex county