A front view of a cypress firefly. This species is one of 27 species found in Indiana. It it common around the Bloomington and Evansville areas. Cypress fireflies are of great concern to conservationists who fear it may be on the brink of extinction. Submitted photo
ANDERSON — There is no activity that coincides with summer quite like catching lightning bugs, also known as fireflies.
Experts have been noticing fewer lightning bugs in the area, leading some to believe they are nearing extinction. But the question of whether that’s actually the case is a complicated one.
“Yes and no,” was the short answer given by Richard Joyce, endangered species conservation biologist for the Xerces Society for Invertebrate Conservation.
“When we talk about fireflies disappearing, there are two big issues,” he said in elaborating. “One is all types of fireflies becoming less common, so there are fewer fireflies out there and fewer places where you can find fireflies.
“That doesn’t mean fireflies are going to disappear altogether,” he added. “There are fewer of them doing what they need to do in the ecosystem and fewer chances for all types of people to enjoy seeing fireflies.”
Some fireflies are of special concern.
In 2021, Xerces Society for Invertebrate Conservation evaluated the extinction risk of 128 species of fireflies in the United States and Canada. The study highlighted 14 species that are facing extinction. Two of them were considered threatened, and at least 33 were of concern.
Indiana is home to 27 species of fireflies, Joyce said, including the critically endangered cypress firefly.
This species is common in southwestern Indiana, near Bloomington and along the Ohio River near the Evansville area. It is seen mostly in cypress swamps and other wetlands.
Advocates fear Indiana’s wetlands are under attack both on legislative and environmental fronts.
A state law that took effect last year relaxes protections on certain wetlands, making them ripe for development, to the dismay of advocates.
Joyce named the destruction of wetlands is as a reason for the cypress firefly’s decline.
“It’s a mix of wetlands being destroyed, too much groundwater being taken out of the ground,” he said. “Other threats could be affecting them indirectly like pesticides or light pollution.”
Joyce said light pollution is often overlooked in studies and discussions focused on insect health, which tend to center around the use of pesticides.
Light pollution is characterized by an unwanted amount of artificial or manmade light in an area.
Most of Indiana’s fireflies are bioluminescent, meaning they glow. The most common example are lightning bugs that release a flickering light from their bodies sporadically, which acts as a courtship signal.
“The males are f lying around signaling their availability using these flashes,” said Sarah Lewis, a professor of biology at Tufts University who specializes in firefly conservation. “Females flash back in return.”
Bright artificial lights like those in cities prevent lightning bugs from seeing one another’s flashes, interrupting their reproductive cycles.
The fireflies will then move away from the area to compensate.
Not all firef lies light up; some are always lit, others do not light up at all. At least eight of Indiana’s 27 species do not light up once they reach adulthood. They are called the “daytime” species.
“They are active during the daytime,” Joyce said. “Some people might say, ‘That’s not a lightning bug, that’s not a firefly,’ but it’s the same family tree, and during their larval phase, when they’re immature, they still light up.”
The fireflies that glow for long periods of time are the “glow worm” species. They maintain a worm-like body shape but have similar markings to other fireflies.
Despite their pleasant, almost docile appearance, fireflies have an aggressive side. Lewis called firef lies the “pest control of the ecosystem,” due to the fact that they eat insects that, if left unchecked, could become a problem.
The internet abounds with images of fireflies eating small snails and earthworms. Lewis said the juveniles are particularly predatory.
Diets vary according to species; some enjoy the previously mentioned animals plus nectar and pollen, while others enjoy other fireflies.
Not only do fireflies help control pests, they are often considered a key barometer for measuring the health of an ecosystem.
An ecosystem with steady clean water and air supplies and non-excessive artificial light will have more fireflies than areas that do not, according to Lewis.
This means that an absence or declining numbers of fireflies might be cause for concern.
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