The magic — and science — of synchronous fireflies

Summary

Podcast Summary: Short Wave — The Magic and Science of Synchronous Fireflies

Air date: May 25, 2026
Hosts: Regina Barber, Ping Huang
Featured guests: Lynn Frierson Faust (Firefly Field Guide Author), Orit Peleg (Computer Scientist & Biophysicist), Sarah Lewis (Firefly Conservationist)

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Episode Overview

This episode of NPR’s Short Wave dives into the enchanting world of fireflies—focusing on their brief adult lives, the captivating phenomenon of synchronous flashing, and the environmental factors impacting their future. Hosts Regina Barber and Ping Huang share their own magical experiences observing fireflies in Washington, D.C., and Congaree National Park, and discuss what science has uncovered about these bioluminescent beetles with renowned experts in the field.

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Key Discussion Points & Insights

1. An Enchanted Nighttime Adventure

• Regina and Ping describe their night out searching for fireflies along the Potomac near D.C., packed into a cargo bike with a dog (00:21–01:00).
  • "It was a tight fit." — Ping Huang (00:58)
• Regina is struck by the magical, almost fairy-tale landscape created by the fireflies’ lights (01:22).
  • “It feels like a fairy tale. I keep on saying Disneyland, but it really. Yeah." — Regina Barber (01:27)

2. Firefly Life Cycle and Habitat Needs

• Fireflies thrive in warm, humid environments with tall grass and standing water. Droughts are especially harmful (03:37).
• Their life cycle: eggs → larvae (spend 1–2 years underground eating invertebrates) → pupae (weeks) → brief adult phase (~2 weeks) when they become visible and flash (04:00).
  • “They only live two weeks. So if you're not standing in the right place at the right time, looking the right direction, you'll miss them.” — Lynn Frierson Faust (04:53)

3. The Science and Magic of Synchronous Fireflies

• Ping visits Congaree National Park, SC, to witness synchronous fireflies (hundreds of thousands blinking in perfect sync) (05:32–06:01).
• Synchronous fireflies are rare but exist in several U.S. locations. Photinus carolinus is found in the Great Smoky Mountains (rapid bursts and dark intervals), while Congaree features Futurus frontalis (constant synchrony) (06:20).
  • “Carolinas do this explosion of flashes for three seconds, and then the whole forest goes dark for six seconds. The Congery synchrony is constant. Like that.” — Lynn Frierson Faust (06:35)
• Ping describes the moment the fireflies synced: “A rolling wave of lights... at some point, they synced up perfectly, at least to my human eye.” (06:49)

4. How Do Fireflies Sync Up?

• The mechanism is still a scientific mystery, but research (Orit Peleg’s lab, University of Colorado) suggests visual cues and limited communication among neighbors lead to global synchrony (07:33).
  • “They're very small creatures... just by communicating with a small group that are near to them, they're able to create global synchronization, which is just a feat of animal behavior, I think.” — Orit Peleg (08:03)
• Fireflies can sync with artificial LED lights; additionally, pheromones play a role when they’re close (08:29).
• Synchrony has an evolutionary advantage by making mating signals more noticeable, especially given high competition among males (09:12).
  • “For them, it's life and death. If they don't get those eggs in the ground for the next generation, they're done.” — Lynn Frierson Faust (09:12)

5. Conservation and Threats

• Synchronous fireflies at Congaree are doing well, thanks to careful park management (visitor limits, culling feral hogs that destroy eggs) (09:38).
• Many firefly species are not as fortunate. Most U.S. fireflies (~170+ species) are either unstudied or their status is unknown, according to Sarah Lewis (Tufts University) (10:04).
  • About 1/3 of species are well-studied and stable, 10% are threatened, and the rest (60%) are under-researched (10:57, 11:17).
• The “Big Dipper” firefly is an urban success story—unbothered by light pollution due to early evening activity (10:31).
  • "It does fine under street lights, no problem.” — Sarah Lewis (10:47)
• Research gaps are significant due to resource limitations—Lewis’s “Firefly Atlas” project enlists citizen scientists to fill in the blanks (11:17).
  • Volunteers can help by watching training videos and surveying at night (11:47).

6. Primary Threats: Habitat Loss & Light Pollution

• Habitat destruction (from humans or natural disasters) and light pollution are the main threats, especially for habitat-specific species (12:01).
• “They use bioluminescent signals against a background of what used to be dark. And as we light up more and more of the night, it makes it very hard for these flashing fireflies to be able to see each other and to be able to find mates.” — Sarah Lewis (12:26)

7. What Can Listeners Do?

• Ways to support firefly health:
  • Conserve habitat: plant native shrubs, allow leaf litter, and avoid broad-spectrum insecticides (12:57).
  • Reduce light pollution: turn off outdoor lights or use motion detectors.
• Regina is pleased she’s supporting fireflies in her own backyard (13:43).
  • "I'm so excited. I'm doing everything right." — Regina Barber (13:43)

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Notable Quotes & Memorable Moments

• “It feels like a fairy tale. I keep on saying Disneyland, but it really. Yeah." — Regina Barber (01:27)
• “A lot of these species, many of them, they flash 20 minutes a night and that's it. And they only live two weeks.” — Lynn Frierson Faust (04:53)
• “They're able to create global synchronization, which is just a feat of animal behavior, I think.” — Orit Peleg (08:03)
• “For them, it's life and death. If they don't get those eggs in the ground for the next generation, they're done.” — Lynn Frierson Faust (09:12)
• "It does fine under street lights, no problem.” — Sarah Lewis (10:47)
• "They use bioluminescent signals against a background of what used to be dark... it makes it very hard for these flashing fireflies to... find mates.” — Sarah Lewis (12:26)
• "I'm so excited. I'm doing everything right." — Regina Barber (13:43)

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Timestamps for Key Segments

• 00:21–01:07: Hosts describe their nighttime firefly expedition
• 03:23–04:53: Firefly habitats, life cycle and what makes a good ecosystem
• 05:32–06:33: Synchronous fireflies, how their flashing differs by species
• 07:33–08:58: Scientific efforts to decode firefly synchronization with quotes from Orit Peleg
• 09:38–10:57: Conservation status and threats to fireflies; citizen science efforts
• 12:01–12:43: Main threats: habitat loss and light pollution
• 12:57–13:43: Practical advice for supporting firefly populations

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Conclusion

This episode of Short Wave brings together a sense of scientific curiosity and awe, guiding listeners through the magical world of fireflies with personal stories and expert insights. It punctuates the critical balance between wonder and conservation, urging us to foster the right conditions for nature’s tiny, flashing wonders.

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Transcript

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[Ping Huang]

You're listening to Short Wave from NPR.

[Regina Barber]

Hey, Shortwavers. Regina Barber here. And a few weeks ago I went on a wild nighttime ride. We're in this like cart that this lady is biking us around with a dog and we're looking for bugs. Friend of the show and wonderful beloved reporter Ping Huang was there.

[Ping Huang]

We are loaded up here in the cargo wagon.

[Regina Barber]

Cargo bike, cargo bike. And we are very tightly pushed in. And Ping is a patient, patient woman and she has a dog on one side of her and me smushing her on the other side.

[Ping Huang]

It was a tight fit.

[Regina Barber]

It was. I felt terrible pain because you had organized this trip to see something very specific and very special.

[Ping Huang]

It's true, Gina. We were out on a bike trail at 9pm on a weekday for a reason. And even though there were cars zooming past us, planes flying overhead, the conditions were actually totally perfect.

[Regina Barber]

They're magical. Like I'm looking out into the marsh and I'm seeing all these like the darkness and bushes but. And then you just see like pops of light. It feels like a fairy tale. I keep on saying Disneyland, but it really. Yeah. It was the magic time of summer in and around Washington, D.C. when you

[Ping Huang]

can see fireflies, hundreds of them, thousands of them, blinking their belly lanterns on and off. So long as you know where to look.

[Regina Barber]

Today on the show, the brief and wondrous adult lives of fireflies. We'll take you on a trip down the east coast to see some special

[Ping Huang]

species and we'll talk about why some are endangered and how you can help.

[Regina Barber]

You're listening to Shortwave, the science podcast from npr.

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[Regina Barber]

ago, on a hot, humid night, we saw an incredible firefly show, AKA lightning bug show. And seriously, Ping, it was this random little patch of dense forest, like sandwiched in between the airport and the parkway.

[Ping Huang]

Right. That little protected marsh between the bike path and the Potomac river was actually the perfect habitat for some fireflies. So there's a lot of different species, but what they all seem to have in common is a love for warm, humid environments. Maybe some tall grass and definitely some standing water. Seriously, one of the big enemies of fireflies is drought.

[Regina Barber]

So why is water so important to fireflies?

[Ping Huang]

Well, I say it's the water and the dirt, and both of these are important to their life cycles. So fireflies are beetles, and so they've got that four part life cycle. They start as eggs, then they hatch as larva. And the larval stage is actually where they spend most of their lives. They can spend up to one to two years crawling around underground eating other invertebrates, and then they burrow down generally into the ground. This is called their pupal stage, and it can last a couple of weeks. And this is where they really transform themselves. Then they emerge as full adults, and that's when people like us walking around at night can see them flying around and flashing in fields and trees. I spoke with Lynn Frierson Faust. She's author of A Firefly Field Guide to the Eastern and Central US And Canada. And she says that adult stage is relatively brief.

[Lynn Frierson Faust]

A lot of these species, many of them, they flash 20 minutes a night and that's it. And they only live two weeks. So if you're not standing in the right place at the right time, looking the right direction, you'll miss them.

[Regina Barber]

Yeah, I mean, it was a brilliant light show that we saw a few weeks ago, and we caught like the tail end of this year's peak of fireflies in Northern Virginia.

[Ping Huang]

Right, right. And right now it doesn't look like that anymore. And when the fireflies peak depends a lot on how hot and humid it's been in the weeks and months just before it.

[Regina Barber]

Okay, Ping, So those weren't the only fireflies you saw this summer, though, right? I know you're dying to tell me more.

[Ping Huang]

Yes, absolutely. So you're right. Earlier in the season I actually went on a trip looking for fireflies down at Congaree national park, which is near Columbia, South Carolina. Since further south, where it's hotter and humid, the fireflies come out earlier. And I went to see a specific behavioral phenomenon, synchronous fireflies. These are hundreds of thousands of fireflies that are all coordinating across a large expanse of nature. So they're blinking all at the same time.

[Regina Barber]

Oh, that sounds really, really cool. Can you only see them in South Carolina?

[Ping Huang]

Okay, well, they're rare, but they're not that rare. So there's just a few species of synchronous fireflies in the U.S. congre, where I went, has one kind, and the Great Suwaki Mountains in East Tennessee has another. Lynn Firestone Fest has seen both kinds.

[Lynn Frierson Faust]

What the Great Smoky Mountains national park has is Photinus carolinus. That is completely different from what is here at Congre is Futurus frontalis. Different genus, different everything.

[Ping Huang]

She says that even the way that they flash is different.

[Lynn Frierson Faust]

Carolinas do this explosion of flashes for three seconds, and then the whole forest goes dark for six seconds. The Congery synchrony is constant. Like that.

[Regina Barber]

Weird. Yeah.

[Ping Huang]

And, Regina, that's exactly what I saw. When it got dark, like, really dark in the forest, I started seeing these little flashes in the trees. You know, at first, it was like a couple of them blinking randomly. And then as more and more of them joined in, I started to see this pattern emerging, like a rolling wave of lights. And then at some point, they synced up perfectly, at least to my human eye, and they were all flashing at once. And that was a pattern that they kept up for a little while before it just sort of went back through the cycle all over again.

[Regina Barber]

It makes me think of those, like, drone fireworks.

[Ping Huang]

I mean, it did look like LED lights a little bit.

[Regina Barber]

Yeah. How are they coordinating, though? Like, how are they doing this?

[Ping Huang]

Well, that's still kind of a mystery, something researchers are trying to figure out. So when I was down at Congaree, I met up with Orit Paleg. She's a computer scientist and biophysicist at the University of Colorado in Boulder. And Orit had come to the Congaree with some folks in her lab to study how this firefly synchrony works. She says that there does seem to be this evolutionary advantage to having a whole swarm of fireflies blinking at the same time. It boosts their signal, makes them more visible to their mates down on the ground.

[Orit Paleg]

And we're trying to understand how they manage to do it. They're very small creatures. They have limited visual perception, and they certainly cannot communicate directly with all the other fireflies in the swarm. But somehow, just by communicating with a small group that are near to them, they're able to create global synchronization, which is just a feat of animal behavior, I think.

[Ping Huang]

Areit says that visual cues are a big part of it, and she says they know this because they can actually get fireflies to flash and sync with LED lights.

[Lynn Frierson Faust]

Wow.

[Ping Huang]

When the fireflies get closer, they also communicate with chemicals, pheromones too. But what's really cool about this is that there doesn't seem to be one leader in the pack. Arete has taken videos from within and around these flashing swans. She's slowed them down, and she says that it seems like it can really originate from all kinds of different places in the pack.

[Regina Barber]

This is, like, fascinating, but it also sounds like really magical to witness.

[Ping Huang]

It was. It was completely magical for me. Beautiful. But as Lynn says, the fireflies aren't actually doing it for our benefit.

[Lynn Frierson Faust]

I'm sure they have just a few minutes each night to find a mate. And sometimes it's as many as 100 males to one female. You know, we think it's beautiful and we love looking at it, but for them, it's life and death. If they don't get those eggs in the ground for the next generation, they're done.

[Ping Huang]

Now, unlike some other firefly species, the synchronous fireflies at Congaree are actually doing pretty well. The park started limiting the number of visit after they realized that overcrowding was disturbing the fireflies. And they've also been culling feral hogs who root around in the dirt and destroy firefly eggs.

[Regina Barber]

Wow. Okay, so these are well known, well studied fireflies protected by the park. Are there firefly populations that aren't so lucky?

[Ping Huang]

Yes, most of them, I would say. So for some context, I called up Sarah Lewis, who's a professor emerita at Tufts University, and she studied fireflies for many years, and now she's actually focused on conserving them. Now, Sarah Lewis says that all the fireflies I saw this summer are the fireflies that are doing okay. I was telling her about this, like, droopy, swoopy firefly I've been seeing in D.C. and she was like, oh, yeah, that's the Big Dipper firefly.

[Sarah Lewis]

It's an urban firefly and it doesn't really care about light pollution. We think one of the reasons for that is because it flies at just at sunset where it's really, actually still quite, quite light out. And so it does fine under street lights, no problem.

[Ping Huang]

Now, Sarah says that out of the 170 or so firefly species that are in the US about 1/3 fall into this category. Well studied, doing fine.

[Sarah Lewis]

On the other hand, there's about 10% of us fireflies that are not doing so well that are some degree of threatened with extinction.

[Regina Barber]

Okay, so 30% are fine, 10% are not. What about this other 60%? About.

[Ping Huang]

Yes, math. Well, Sarah says there are just huge gaps in our knowledge on these other fireflies because the research is really time intensive and it's not well funded. Now, there is a movement to get community scientists involved. Sarah and some others have launched a project called Firefly Atlas. It's enlisting volunteers to go out and survey for 13 specific firefly species that are considered data deficient.

[Orit Paleg]

Wow.

[Regina Barber]

Okay, so you can just go collect data for this project?

[Ping Huang]

Well, you do have to register, and then you also have to watch this, like, hour long training video that tells you what data to collect.

[Regina Barber]

Okay.

[Ping Huang]

And then you go out at night to look for them.

[Regina Barber]

So for the fireflies that aren't doing so well, do researchers know why?

[Ping Huang]

So Sarah says that there's two things in particular. Habitat destruction and light pollution. And that habitat destruction can come from human development or natural disasters and droughts. And it can hit some fireflies, particularly because there are certain species that really need the specific conditions in like a cypress swamp or a freshwater wetland to survive. And then there's light pollution.

[Sarah Lewis]

They use bioluminescent signals against a background of what used to be dark. And as we light up more and more of the night, it makes it very hard for these flashing fireflies to be able to see each other and to be able to find mates.

[Regina Barber]

Okay, so this sounds like big environmental issues. Is there anything I, like me, I can do to help, aside from like, helping the scientists collect data? Like, I love these fireflies, especially the ones we saw, like, and I want to keep them going.

[Ping Huang]

Yeah. So, Regina, if you're in a place where fireflies can live and you have a backyard or a front strip or you're responsible for a patch of nature somewhere, you can help to make it a good firefly habitat. Sarah says that this means having shrubs, native plants, and really critically not spraying your lawn with broad spectrum insecticides, which can kill fireflies too. You know, another thing you can do to help is to leave some leaf litter around, make it a place where firefly larvae and the things that they eat can thrive. And you can also, of course, cut down on light pollution in your home or in your environment so you can, you know, switch off the outdoor lights, use motion detectors so they're not constantly on anything really, to help these beggars grow to adults and find their mates so that their cycles can continue on.

[Regina Barber]

I'm so excited. I'm doing everything right. Thank you so much for this reporting, Ping.

[Ping Huang]

Thanks for coming with. It's been so much fun.

[Regina Barber]

This episode was produced by Rachel Carlson, it was edited by Burleigh McCoy and fact checked by Ping. Kwesi Lee was the audio engineer. Special thanks to our local tour guides, Cameron Taylor, Josephine Liu and Judd Isbel with Friends of the Mount Vernon Trail. I'm Regina Barber. Thank you for listening to Short Wave from npr.

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