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Firefly Populations Are Blinking Out

Blink and you’ll miss them this summer. Around the world, people are reporting that local firefly populations are shrinking or even disappearing.
The insect’s dilemma first came to the world’s attention at the 2010 International Firefly Symposium, where researchers from 13 nations presented evidence of firefly population declines and declared “an urgent need for conservation of their habitats.” Since then, additional conferences and several scientific papers have documented regional firefly disappearances, and at least two citizen-science projects are attempting to document the phenomenon, but the full scope of the problem remains to be uncovered, says firefly researcher Ben Pfeiffer, founder of, a website about the decline of the insects, also called lightning bugs.
“It’s worrying,” said Pfeiffer. “When people see a habitat that’s got three, four, five different species of firefly flashing, each with a different flash pattern, it’s an amazing thing. It changes their lives, but few people get to see that anymore.”
The exact extent of the decline is unknown, but early indications suggest that lightning bug populations have shrunk in many places and disappeared from others. “Everyone is reporting declines,” said Eric Lee-Mäder, codirector of the pollinator program for the Xerces Society for Invertebrate Conservation.
The causes, however, appear to be clearer: a combination of habitat degradation and loss, light pollution, destruction of water tables, and pesticides, Pfeiffer said.

(Photo: Terry Priest/Flickr)
“You can wipe fireflies out really easily,” he added. “It’s not hard. You’ve got a one-acre plot, and you put a house there. Good-bye, fireflies. They’ll never be there again.”
The loss of fireflies, which are beetles, can have multiple effects on their ecosystems. For one thing, some firefly species—there are at least 170 in the U.S.—play a role in pollination. They’re not as essential as bees, but they help pollinate milkweed, goldenrod, wild sunflowers, and other species.
More important, however, firefly larvae are voracious predators that live in the ground and eat slugs, snails, worms, aphids, and other problem critters that would otherwise grow out of control. “I call them nature’s pest control,” Pfeiffer said. (On the other side of the dinner table, fireflies are important food sources for species such as bats and spiders.)
The insects play a role in human health as well. Two of the enzymes fireflies use to create their bioluminescent flashes—luciferin and luciferase—are used to track the growth of cancer tumors, among other things. Fireflies have also been used to help detect bacteria in food products.

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Lee-Mäder said he suspects that decades of overzealous collection by the medical industry may have contributed to fireflies’ decline. Pharmaceutical companies used to pay bounties of up to a penny per firefly to collect their chemicals for biomedical use. The pharmaceutical company Sigma Chemical Company collected up to 1 million fireflies a year and sold the chemicals for about $260 an ounce, according to a 1975 report in the Milwaukee Journal.
“If you do the math, that’s a lot of insects,” Lee-Mäder said. “You multiply that over a pretty wide area and add these other stress factors, and there’s no doubt that it has had a major impact on populations. We just don’t know what that impact is yet.”

A 2013 study published in Ecological Modeling found that some firefly populations failed when medical harvest rates exceeded 60 percent.

Why don’t we know more about firefly declines? “Research drives our understanding of these sorts of things, and money drives research,” Lee-Mäder said. “So much of our understanding of entomology is driven by the control of pest insects, which comprise less than 1 percent of the insect species on Earth. There just isn’t a financial base to understand what’s going on.”
Some researchers are trying. The Museum of Science in Boston has an ongoing “Firefly Watch” project that lets people around the country report firefly sightings and help to develop a database of lightning bug distribution and abundance.

Meanwhile, Pfeiffer’s offers tips on how people can help fireflies in their area, including turning off outside lights, establishing ponds and other useful water features, and allowing leaf litter to gather, giving firefly larvae an opportunity to grow.

Pfeiffer said the firefly story is not all bad news and pointed out that some populations are increasing. At least one species, known as the common eastern firefly, is doing fairly well because it is adaptable and can move into areas where more fragile firefly species can no longer survive.
That may sound like good news for that species, but Pfeiffer called it a disappointing change because the common eastern firefly is replacing species that served specific habitats. “You lose the genetic diversity of these unique species,” he said.
Pfeiffer said he doubts we’ll lose all fireflies, but the planet is losing variety and possibly some entire species along the way. “Nature is capable of producing some really amazing things, and those things are disappearing,” he said.