Fireflies have a good year, but they’re in decline
Blinking with heatless light in the dark of midsummer nights, fireflies seem visitations from some fairy-world, explicable by spells and sorcery more than science. But they are real. And despite a strong showing this summer, scientists believe they, like so many natural wonders, are diminishing.
“I catched one once at my friend’s house,” said Emma Check, a five-year-old at the Ridgefield Parks and Recreation summer day camp.
“We got them in jars and then my mommy let it go when I was sleeping, because we had it for a very long time.”
“I like that when I go to the big window in my living room I can see their flickering,” said Lillian, a camper whose parents asked that her last name not be used.
“They’re not hot,” said her sister, Alexandra.
“We used to call them lightning bugs in the Bronx,” said Jane Byrnes, an administrator at the Ridgefield Recreation Center, where The Press asked some folks about fireflies on Friday, Aug. 2. “Lightning bugs in the Bronx, fireflies in Ridgefield.”
Byrnes is among the people who’ve gotten a sense there are a lot of fireflies this year.
“There was a while a few years ago you didn’t see any fireflies at all… They seem to be coming back.”
“Every night, there’s beautiful fireflies outside,” said Sara Kessler of Manor Road, who’d been for a swim at the rec center pool.
“I have fireflies every night — I wouldn’t say an abundance of them.”
Ridgefield Conservation Commission member David Cronin also observed that 2019 looks like a good year for fireflies.
“I noticed a while ago that they seemed to be abundant this year,” Cronin said. “But like other things they aren't doing well in general.”
A very good year
If the glowing little miracle beacons of summer really are disappearing from the world’s skies — as was the buzz all over the Internet just a couple of years ago — there seems to be wide agreement that they’re making a good show of it in summer 2019.
A lot of folks here the northeast who’ve spent time outside so far this summer have gotten a sense that the blinkin’ little disco buggers with the built in glow-lamps are seemingly everywhere this year, at least in Connecticut and surrounding states, as well as farther north in Canada.
Fireflies are a midsummer thing and will soon be gone until next summer, so now’s the time to go outside and gaze into the summer night sky: lightning bugs, the little critters kids collect in Mason jars, are back in a big way.
And just for the record, it’s about love. All those slyly-winking little lights in the summer night are mating calls — the call and response of sexy little glow worms desperately trying to hook up with their mates so they can propagate their species.
How can they be so prevalent if they really are in decline? For that matter, are they really in decline?
The answer, according to firefly experts, is that, yes, lightning bugs really are in decline over the long term — and yes, they really are everywhere this summer.
Most likely, that’s due in large part to some pretty perfect firefly conditions this past spring and last fall, said Sara Lewis, professor of evolutionary and behavioral ecology at Tufts University. Lewis is a respected expert in the field, deliverer of a Ted Talk on fireflies — and a New Haven native.
“It does turn out that in a lot of parts of the U.S., this is a really great year for fireflies,” said Lewis, a wildlife biologist, author of “Silent Sparks: The Wondrous World of Fireflies” and director of the Lewis Lab at Tufts, which focuses on the interface between behavior, evolution and ecology.
“That’s true across a lot of Midwest, and of course New England,” Lewis said.
It’s also the case in the area around Ottawa, Ontario, in Canada, among other places, according to the Ottawa Citizen.
In Connecticut, the peak of “firefly season” is from mid-June through mid-July, said Andy Moiseff, associate dean and professor of physiology and neurobiology at the University of Connecticut Center for Environmental Sciences and Engineering.
This year “has been a great year” for fireflies,” although “we just don’t know exactly” why there have been so many fireflies this summer, Moiseff said.
“But it was much wetter this year,” Moiseff said. “I just have to look at my lawn to know that. ...
“Even with climate change, it doesn’t mean that you don’t have some seasons that are different,” he said.
All around the world, “Everybody loves fireflies,” said Lewis, pointing out that they don’t bite. “They’re the only insect that everybody can get behind. ... It’s not just in the U.S. ... Everywhere around the world, kids have that same connection to them.”
Lewis, for one, can’t imagine a world without fireflies — and she’s among the scientists around the world working on ways to ensure their survival.
“It’s really a confusing thing that fireflies could be doing well in the short term but declining in the long term,” she said, but “firefly populations fluctuate from year to year.”
Lewis, one of the researchers working with the Mass Audubon’s Firefly Watch Citizen Science Project, is not the only bug expert who has noticed this year’s firefly bumper crop — and lay people have noticed it, as well.
“I’ve had conversations with clients here at the information office ... about how isn’t it nice that the lightning bugs are back,” said Gale Ridge, an entomologist with the Connecticut Agricultural Experiment Station in New Haven.
A resident of Bethany, Ridge has witnessed this summer’s lightning bug bounty at home, as well.
“It’s actually glorious,” she said.
Ridge also believes that weather conditions are responsible for this summer’s show. “We didn’t really have a very severe winter, and when it was cold there was a nice blanket of snow to protect them,” she said. “Certainly, a wet spring would be favorable to the larval stage, which is a predator of soil organisms such as earthworms and sow bugs.”
Less pesticide use
She also believes that the decline of the use of lawn pesticides also could have contributed to this summer’s return of fireflies, although “clearly, that would have to be researched.”
Lewis, whose family lived in New Haven when she was born, thinks it’s important to dispel certain firefly myths, including that “fireflies” are just one thing.
In fact, “in the United States, there are 200 kinds of fireflies” — and there about about 2,000 varieties around the world, she said.
New England alone is home to about a dozen different varieties of fireflies, Lewis said.
Lewis also believes its important to dispel a second myth, that fireflies “just spark into existence for a few weeks in the summer” and then disappear, and “who knows what happens to them.”
In fact, before you ever see them, fireflies spend up to two years living underground in the larval stage , Lewis said. “They are carnivorous, feed on earthworms and snails and slugs.”
They also require plenty of moisture, so the fluctuations in their population tend to be tied to moisture conditions in the spring preceding the summer, and the autumn prior to that, she said.
“We also know that too much water is not good. So just the right amount of moisture makes for a good firefly season,” Lewis said.
For the species of fireflies that are declining, major threats include the loss of their habitat, light pollution and pesticides.
“So if you grew up where there’s a meadow or a marsh or a forest where there are fireflies,” loss of those things to paving and development is the major threat to fireflies all around the world, including in New England, she said.
Light pollution makes it harder for fireflies to communicate with and find their would-be mates, and reproduce, Lewis said.
Pesticides kill insects “and fireflies are insects,” she said. “Any kind of broad spectrum insecticide that you use on your lawn is going to kill fireflies.”
UConn’s Moiseff said it’s important to know that with fireflies, the relative health of a population “depends on the species. Different species are different.”
And even within Connecticut, the species that are most prevalent can vary from place to place, so the types of fireflies Moiseff sees near his home in Vernon might not be the same as what Ridge sees in Bethany.
“The tricky part is, most of what we know about the population is very much anecdotal,” Moiseff said. “It’s very localized.”
But over the long term, Moiseff added, “I think it’s true that there probably are decreasing populations.”
Brett Ortler, author of “The Fireflies Book: Fun Facts About the Fireflies You Loved as a Kid,” said he’s also seen more fireflies than usual this summer — and he lives in Minnesota, where he said this has also been a banner year for another one of the world’s natural wonders: dragonflies.
“My folks have a lake place and when I went up there” fireflies were everywhere, he said.
Studying the reasons why is difficult, however, in part because “adults only live for a matter of weeks ... and tracking them down is really hard,” he said.
But Ortler said that whatever’s going on with fireflies isn’t all that different from the fates of many other animals.
“As a general rule, most animals’ populations have declined” over the years, he said. But “I’m optimistic that if people don’t spray and if people make their back yards like a habitat, insects might do a little better.”