A long, slow-moving trail of light created by a blue ghost firefly is visible on a night in June near Cincinnati. Fireflies produce a chemical reaction inside their bodies, allowing them to light up. Carolyn Kaster/Associated Press

Where have all the fireflies gone?

That’s the most common question that Don Salvatore, the retired co-founder of Firefly Watch, fields on his guided walks. Over and over, people tell him the night skies of summer have lost the green and gold flashers that were so plentiful when they were children.

But is that true? According to Salvatore, scientists don’t have enough information to know for sure. The firefly is a beloved insect – up there with ladybugs, butterflies and bees – but still an insect. Science has never prioritized the study of insects, he said. Not even the popular ones.

“People know three things about fireflies,” said Salvatore, 72, who retired five years ago to Scarborough. “They come out at night, they flash, and people love them. And only one of those is exclusively true. The public doesn’t realize some come out during the day and not all of them flash.”

Sadly, since they are neither pollinators nor pests, scientists don’t know much more about them, either.

BACKYARD RESEARCH

That is why Salvatore launched Firefly Watch. His employer at the time, the Boston Museum of Science, was looking for its first citizen science project. Salvatore decided to harness the public’s affection for the firefly to collect raw, backyard data that could help scientists better understand these insects.

After 17 years of citizen censuses and a slowly growing body of independent research, scientists at the International Union for Conservation of Nature agree that fireflies appear to be in decline, with 14 species in North America and 14% of all global species believed to be on the verge of extinction.

But this number could be much higher because scientists don’t have enough information to evaluate the extinction risk for more than half of all firefly species, according to Candace Fallon, senior conservation biologist with Xerces Society, the science nonprofit that has taken over Salvatore’s Firefly Watch.

If these data-deficient species follow the same pattern as the well-documented species, more than 1 in 3 North American fireflies are at risk of extinction, said Fallon, who was lead author in IUCN’s study. But even the better-studied ones, and the ones thought to be endangered, need more study, she said.

It turns out, counting fireflies is really hard, even for those who know what they’re doing. At night, it can be almost impossible to track a single firefly among many with the naked eye, and be certain you’re not counting one firefly many times or conflating the flash patterns of two different species.

So Xerces and IUCN put certain fireflies on its Red List of Threatened Species for reasons other than low counts, like loss of habitat for a species that is habitat dependent, Fallon said. Overall, researchers blame the decline on habitat loss, pesticide use, light pollution and climate change, especially sea level rise.

“We have almost no numbers, which is really frustrating and really dangerous for fireflies,” Fallon said. “Without historical reference points, we can’t say how they’re doing now, even if we had the grant money to buy the cameras and equipment needed for accurate counts. But that’s the story of insects, generally.”

A male firefly of the Photuris genus pauses on a leaf in June near Cincinnati. Carolyn Kaster/Associated Press

Under certain scenarios, climate change could make Maine more welcoming to fireflies, which generally prefer warm, wet conditions, Fallon said. But extreme weather fluctuations – such as periods of drought punctuated by torrential rainstorms – could harm Maine’s firefly outlook, she said.

The inundation of Maine’s coastal marshes by rising seas also could destroy habitat for certain species.

Since taking over Salvatore’s census, Xerces has renamed it Firefly Atlas, beefed up the data collection protocol and launched a national conservation effort. The new data requirements put this project just beyond the ability of most backyard enthusiasts, but it gives the conservation campaign more teeth.

FIREFLY TOURISM

Salvatore, who moved from Massachusetts to Maine in 2019, still leads seasonal firefly walks in June and July for land trusts, garden clubs and public libraries in his adopted state. He keeps urging people to count fireflies to build public support for Xerces’ serious conservation campaign.

Fallon and Salvatore both believe that firefly tourism could help capture the public interest, and dollars, needed to bring about more research into these beloved strangers. Firefly festivals and sanctuaries have popped up along the East Coast, tapping into the public’s affection for fireflies.

After two decades of talks, the soft-spoken Salvatore knows what his audience wants. Conservationists want to know if fireflies are in decline and why. Gardeners want to learn how to attract fireflies (let the grass grow, don’t use pesticides, nix the outdoor lights). Children are all about the flash and the gore.

But like any educator, Salvatore always begins with the basics.

Fireflies or lightning bugs are neither flies nor bugs, but flying beetles. There are more than 170 species of fireflies in North America, and more than 2,200 species worldwide, with new ones being added often. Salvatore may have identified a new species himself, but he wants to trap more specimens to be sure.

The best-known species are flashers, but some species, especially those out in the U.S. West, only show off their bioluminescence capabilities as larvae, and it comes off as more of a glow than a flash. The non-flashy kind live in the eastern U.S., too, including Maine. One local species comes out in winter.

Maine is believed to have 15 species of fireflies, including 11 flashers, Fallon said. The state doesn’t have any species on IUCN’s red list, but it’s home to five species that researchers don’t know enough about to classify as safe or not, Fallon said. Of those, the marginal and the wiggle dancer are likely in danger.

The most common firefly species in Maine – the kind you probably see in June and July in the suburban understory – is called the big dipper firefly, which got its name because it dips as it flashes. It will probably benefit from Maine’s warming, increasingly wet climate, Fallon said.

Fireflies have two pairs of wings. The outer wings are protective shells. When the beetle takes flight, the outer wings are held up like airplane wings to steer the beetle’s flight, which is powered by a pair of soft inner wings that beat rapidly to propel the beetle’s movement.

The firefly has four life stages – egg, larva, pupa and adult – with each making use of a different part of their habitat. Any habitat disruption, like applying a new pesticide, clear-cutting a woodlot, or haying a field, can decimate a local firefly population in a single season.

The fireflies you treasured as a child are actually quite ruthless, Salvatore said. For example, the larvae are carnivores, using a toxin to stun and then eat their meal of worms, snails, and slugs while still alive. When attacked, fireflies can exude a toxin that can glue a predator’s mouth shut.

Flashers use a protein called luciferin that can produce light when broken down by a specific enzyme. Now manufactured in factories, these chemicals can be used to make glow sticks, detect bacteria, and even track cancer drugs.

Fireflies use the flashing to find a mate. Each species has its signature flash, with a distinct color, length and number of flashes displayed at just the right time of night, using the right flight pattern. That is how males find a female of their own species in the crowd.

The male that flashes the brightest and the longest within a species pattern is believed to deliver the most sperm to fertilize a female’s eggs and the food needed to feed them, making him the preferred mate. If a female likes what she sees, she turns on her own light.

But certain species of fireflies are tricksters. This larger type of firefly – which is common in Maine –will mimic the light of a smaller species to lure them in, rip off their heads and drink their blood. Not only is this gruesome, but the false flashing complicates a citizen scientist’s ability to identify a species at night.

“There is so much people don’t know about these beautiful insects,” Salvatore said. “Not all of it’s pretty.”