Environmentalists are pushing for a rare Bethany Beach firefly, which has a distinct “double greenish flash,” to be included on the federal endangered species list. (Christopher M. Heckscher/Delaware State University via AP)

Peering through the darkness under the faint light of a peach-colored moon, wildlife biologist Jason Davis spots a telltale green flash in the bushes.

Quick as a flash himself, Davis arcs a long-handled mesh net through the humid coastal air, capturing his tiny target.

Ignoring the mosquitoes, Davis heads to his pickup truck, opens up a notebook-size metal testing kit and examines his find. Two minutes later, he makes his pronouncement.

“That is what I am calling bethaniensis,” he declares.

Photuris bethaniensis,” also known as the Bethany Beach firefly, was first identified in the 1950s and has been found only in a sliver of southern Delaware coastland. Now environmental groups are shining a beacon on the luminescent beetle with a distinct “double greenish flash.” Its unique habitat, they say, is threatened by coastal development, sea-level rise, invasive plants and insecticides.

The Center for Biological Diversity and the Xerces Society for Invertebrate Conservation, both based in Oregon, are pushing for the federal endangered species list to include its first firefly.

Their petition to the Department of Interior says the Bethany Beach Firefly “is at immediate risk of extinction” from the “imminent destruction” of much of its habitat, noting plans to build beach homes in one of the largest of the rare freshwater swales where the firefly has been found. The swales are shallow depressions tucked among sand dunes and fed by rain and underground water.

A developer has built a wooden road on pilings in one of the freshwater wetlands in Bethany Beach, Delaware. This is one area where the Bethany Beach firefly has been found. Environmentalists would like to stop the development. (Gary Emeigh/AP)

The Bethany Beach firefly is on Delaware’s endangered species list, but that makes it illegal only to transport, possess or sell them. The state has been unable to stop the building project because, unlike other states, Delaware doesn’t regulate most freshwater wetlands. State environmental secretary Shawn Garvin suggests that should change.

“This is just an example of why the state would like to have some ability to engage in these types of projects in nontidal wetlands,” Garvin said.

“That firefly was at the top of my list to do a petition for fireflies,” said Tara Cornelisse, a scientist with the Center for Biological Diversity. “But when we were certain about the development going on in one of its habitats, that’s when we elevated it to an emergency listing.”

Immediate federal protection is unlikely, and the developer is moving forward with construction. The Interior Department is supposed to decide within 90 days of filing if the government will launch a year-long review. Getting on the list takes longer. “I think the average is 12 years,” Cornelisse said.

The petition says the Breakwater Beach development is destroying one of only seven freshwater swales where the firefly has been found.

“They were superabundant in that one spot,” said Christopher Heckscher, an environmental scientist at Delaware State University who “rediscovered” the Bethany Beach Firefly in the late 1990s.

A lawyer for the developer questioned the petition’s timing and said it uses limited data from two decades ago.

“Breakcap LLC has no reason to believe that any fireflies live in or along the interdunal swale within Breakwater Beach, let alone that Breakwater Beach is critical habitat for any species,” attorney Francis X. Gorman wrote in an email.

Davis, a biologist with Delaware’s environmental department, began a survey in late June. He said his team caught and released about a dozen Bethany Beach fireflies at four of the first 20-odd sites they checked.

“I’m optimistic that we’ll hopefully find some more,” said Davis, who aims to survey at least 40 freshwater swales. He’s been limited to state coastal parks, because no private property owner has given him permission to survey their land.

Photuris bethaniensis wasn’t considered a separate species until Frank Alexander McDermott published his findings in a Smithsonian scientific journal in 1953. He described a beetle with a distinct “double greenish flash” he first spotted at the north end of Bethany Beach in 1949. It took him several years to capture enough to make a scientific determination. Few paid much attention to the firefly until Heckscher began a three-year survey in 1998.

“No one knew if it was still around or how common it was at all,” he said. “Pretty much because no one had been looking for it.”