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Fewer fireflies lighting up Iowa’s summer nights
Decline of bioluminescent beetles may help humans understand toll of climate change and development on insects
Like many Iowans, State Entomologist Robin Pruisner remembers warm July nights of catching fireflies in glass jars to see their bioluminescent glow.
“As a farm kid in Iowa, I always had a jar — or four — of insects including fireflies,” said Pruisner, 53, who grew up near Dike in northeast Iowa. “It makes me wonder how many entomologists found their way to their career by starting out as a little shaver with a jar with holes in the lid and collecting fireflies?”
Call them a gateway bug.
You’re not alone if you think there are fewer fireflies than there were in previous decades. At least 18 species found in North America are threatened with extinction due to habitat loss, light pollution and climate change, according to a study published in 2021 in the journal PLOS ONE. For many other firefly species, there’s just not enough data to determine if they are at risk.
“With emerging evidence for widespread declines in insect populations, there is an urgent need for formal assessments to inform the conservation status of firefly species and estimate their extinction risk,” noted the study.
There are about 2,200 species of fireflies — or lightning bugs, if you prefer — in the world. Of those, 170 species live in North America and about six are in Iowa.
The most common firefly in Iowa is the Big Dipper, a species whose male flashes about two feet from the ground, dips down slightly and then goes up, making a “j” shape, said Donald Lewis, an emeritus professor and extension entomologist for Iowa State University.
“Males and females recognize their own species by a species-specific light pattern,” Lewis said. “It could be the number of flashes, the duration or the interval between flashes.”
Fireflies produce the glow by taking in oxygen that starts a chemical reaction that creates a bioluminescent enzyme, Scientific American reported.
Fireflies can’t survive in a jar, even one with holes
There are a few misnomers about fireflies. They aren’t flies and they aren’t bugs. They’re beetles, distinguished by a hard, outer set of wings and mouths designed for chewing, among other differences.
And that thing most of us did when we captured fireflies, punching holes in the jar lid to give them air?
“The dream was you’d create a lantern that would glow throughout the night,” Lewis said, recalling his childhood on a dairy farm in northwest Ohio.
“It was always emphasized you use a jar with a lid that had holes in it. That allowed the fireflies to dry out and die more quickly. If we had put them in a jar without holes, they would have gotten enough oxygen,” he said.
If you do observe fireflies in a jar, consider putting in a moist paper towel or coffee filter. And let them go after no more than an hour, the Iowa Department of Natural Resources recommends.
Iowa photographer has seen firefly decline
Radim Schreiber, a photographer from Fairfield, started photographing fireflies in 2008, capturing their glow with a lowlight camera. In 2010, his “Amber Firefly” photo won the 8th Annual Smithsonian Magazine photo contest.
Now Schreiber, originally from the Czech Republic, travels around the world to photograph different species of fireflies and to exhibit his work. He has worked with the BBC, National Geographic and Discovery and has collaborated on firefly documentaries.
“I have two kinds of photography techniques,” Schreiber said. His close-up images are snapshots of individual fireflies, showing their glowing anatomy. He can only take these images for about 15 minutes at night before it’s too dark.
“When I do landscapes, these are always extended exposure photographs,” Schreiber said. “This could be a single photograph or multiple exposures. If it’s too dark or there are not enough fireflies I can extend my exposure beyond a couple minutes by using multiple exposures.”
Schreiber has observed fewer fireflies in some areas than when he started his work.
“I have seen their decline in Fairfield because of human development and possibly additional light,” he said. “One of my favorite places to photograph was this park called Lamson Woods. A couple of years ago, they put a new sewer line in. They disrupted the firefly habitat and cycle and it will take many years for that to come back.”
Schreiber is saddened by the decline of fireflies — along with loss of ocean coral and other animal species.
“One of the reasons I enjoy doing what I do is I bring joy to people’s hearts,” he said. “I would like to send a message that nature is beautiful and valuable and completely fascinating. We have to protect it.”
Drought, light pollution, loss of habitat threaten fireflies
Fireflies spend 11 months of the year in the larva stage, hiding under mulch, leaves or other decaying organic material and eating slugs, snails, earthworms and other arthropods, Lewis said.
With the development of neighborhoods and strip malls, there aren’t as many of those undisturbed places. Wetlands, intermittent streams and damp ravines can dry out during periods of drought, which much of Iowa is facing.
“For honey bees and pollinators and fireflies I think loss of habitat is the No. 1 problem,” Lewis said. Other factors working against fireflies are pesticides and too much light, which makes it harder for females to find males of their own species.
Many entomologists, including Lewis, think fireflies may be a way to get people to care more about the plight of insects in our changing climate. When Americans started learning about how monarch butterflies were nearing extinction because their food source — milkweed — was disappearing, many started planting milkweed and fostering caterpillars.
“Fireflies are a charismatic fauna,” he said. “People notice them and pay attention to them.”
To provide habitat for firefly larvae, Lewis recommends leaving leaf litter and plant debris in yards and gardens. Iowans also may want to avoid using pesticides to kill slugs in their flower beds because those slugs are a firefly food source.
Other types of fireflies
Blue ghost fireflies, known for their unique blue-white light, exist only around Asheville, North Carolina. Rather than blinking, the blue ghost stays lit for up to a minute at a time, allowing them to “paint” streaks of light, according to Discovery.
Synchronous fireflies live in North Carolina and Tennessee as well as parts of Southeast Asia. They are one of only a couple species in North America that synchronize their flashing light patterns. The flash pattern is five to eight flashes, followed by a pause of about eight seconds. “As more males start joining in, the flashing also will begin to synchronize and entire sections of the forest will be pulsating with light,” the National Park Service reported.
Giant fireflies, found in Southeast Asia, are called that because females can grow up to three inches long. Because the females often don’t fly, they sometimes are called glow worms. They provide a steady, bright light.
Comments: (319) 339-3157; erin.jordan@thegazette.com
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