‘Lost’ firefly spotted in US after nearly 43 years, raises hopes for its survival

In a rare sighting from a meadow at Brandywine Creek State Park in Delaware, U.S. researchers have spotted a “lost” firefly that went missing nearly four decades ago. Scientists consider a species “lost” if it hasn’t been sighted for at least a decade.

​The prolonged disappearance period of nearly 43 years for Pyractomena similis, commonly called a similar firefly, pushed conservationist group Re:wild to include it among its “Most Wanted list of lost species.”

Spotted while sending mating signals

Historically, researchers recorded these flies in several parts of the eastern and southeastern United States, including Washington, D.C., Maryland, Virginia, South Carolina, Alabama, and Mississippi. ​

Scientific records show it was last seen in 1983. Two years ago, researchers began their hunt at two historical sites near Appomattox, Virginia, where the similar firefly had been observed decades earlier. However, the search was unsuccessful.

​The insect was recently rediscovered by scientist Christopher “Kitt” Heckscher and his team, who began their hunt in suitable habitats in Maryland and Delaware.

The search ended earlier this year in June, when Heckscher noticed a striking flash pattern, a typical signal of these insects, in a meadow with grasses, shrubs, and low vegetation that had largely been allowed to grow naturally.

​He noticed eight to twelve male flies were emitting a unique light signal: ten to twenty short, amber flashes in rapid succession. They paused for a brief moment before beginning the next series. Heckscher noted these were courtship signals sent by male fireflies to attract the females during the mating season.

​Recognizing the signals, Heckscher suspected they were ‘similar fireflies’ and confirmed their identity by placing them under a microscope and examining their male genitalia.

Lost due ​to habitat loss, fewer lookouts

Scientists believe there could be multiple reasons for a species to fade away, ranging from as simple as not enough people are looking for them or their numbers are dwindling due to habitat loss.

​In the case of P. similis, both reasons could be true.

​He suspected that the natural habitat of the similar firefly, which are open meadows, fields, or farmland with grasses and scattered shrubs, especially near freshwater such as streams, rivers, marshes, or wetlands, are “not terribly common” anymore.

​Most suitable habitats are being lost to development, intensive agriculture, or frequent mowing. As a consequence, the species might be in decline, he added.

​A 2024 U.S. Fish and Wildlife Service report found that the rate of wetland loss has risen in American states since 2009 and increased by 50 percent. As of 2019, nearly 95 percent of freshwater wetlands cover less than 6 percent of the lower 48 states, which is half the area they covered in the 1780s.

​Besides habitat loss, artificial light at night is a potential threat for this species, which belongs to a family of lightning bugs. Streetlights and lighting on buildings and in gardens can make courtship signals harder to detect, reducing reproductive success, according to the International Union for Conservation of Nature (IUCN). However, this study has not yet examined this aspect.

​Further, the study reports that ‘similar firefly’ is not the only one among the firefly species in the United States and Canada to be lost. There are around 28 more from a total of 178 that remain lost, accounting for around 16 percent.

​The findings were published recently in the Journal of Lost Species.