The Magic of Fireflies: Flashing Lights, Glowing Worms, and Chemical Reactions

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Guest Information

Richard Joyce is an endangered species conservation biologist at the Xerces Society where he works with researchers and land managers to survey for and conserve fireflies, and coordinates many aspects of the Firefly Atlas, a nationwide community-science project. 

Show Notes & Links

In this episode, we focus on the life history of fireflies, the light they create, and what it is like to study them. We also explore the threats to their populations and what people can do to help.

• Firefly conservation
• Firefly Atlas

Transcript

Matthew: Welcome to Bug Banter with the Xerces Society where we explore the world of invertebrates and discover how to help these extraordinary animals. If you want to support our work go to xerces.org/give.

Matthew: Hi, I'm Matthew Shepherd in Portland, Oregon.

Rachel: And I'm Rachel Dunham in Missoula, Montana.

Matthew: Fireflies. Just the word evokes for many people memories of summer evenings filled with magic and awe. From their flashy mating displays to their glowing larvae, these iconic insects have captured our hearts. Unfortunately, fireflies have started to disappear from the landscape. What is causing this decline and what can we do to help?

Matthew: Joining us this week to talk about incredible insects is Richard Joyce. Richard is an Endangered Species Conservation Biologist at the Xerces Society where he works with researchers and land managers to survey for and conserve fireflies, and coordinates many aspects of the Firefly Atlas, a nationwide community-science project.

Matthew: Welcome Richard, it's great to have you here.

Richard: Thanks, Matthew. It's, great to be here and I've enjoyed listening to the show so far.

Rachel: Awesome. Well, to start off, last month we talked about beetles and learned that fireflies are not actually flies, but in fact beetles. But something really special about these particular beetles is that they light up. So, to start with, can you tell us how many different types of fireflies there are and do all of them light up?

Richard: The short answer is we don't know exactly how many species of firefly there are in the world, but the number of described species, so those with a scientific name that are kind of known to science is at least 2,400 and there many, many species that are still being described every year. Especially from tropical regions, like South America and parts of Africa. Within the United States, I think the latest tally is 174 named species.

Richard: And just in 2023, two more species were described. So, it's not a fixed number. And hopefully, it will continue to go up as we get to know our fireflies better.

Matthew: Yeah, I think it is interesting, you think that fireflies is a group of insects that we would know pretty well.

Richard: And yet, it's just saying, we even now we don't know exactly how many species there are which is I guess indicative of the broader situation with so many insects where there are not enough people looking to understand them.

Richard: Yeah, definitely that follows that pattern for insects. And Rachel, I think I missed the second part of your question about whether all fireflies light up. And it really depends, on what time, and what part of the firefly's life you're talking about.

Richard: So, the vast, vast majority of fireflies or beetles in the family Lampyridae do produce light during some part of their lifecycle. For almost all fireflies, that's during their larval phase. There are, groups of fireflies that have probably lost the ability to produce light as adults. And they use other processes or functions to do what they would do with light other ways.

Matthew: What would they do with light? Why do they light up?

Richard: Fireflies light up to communicate. Their light is a message. And the entity receiving that message, or the intended recipient for that message is going to vary depending on what lifecycle, or life stage the firefly is in.

Richard: So, in the first part of their life cycle when they're an egg or a larva. That glow is telling potential predators that they taste really bad, and that they're toxic. So, it's kind of like the warning coloration, the bright orange and black of a monarch butterfly except it's at night. So, you're giving a warning signal to predators.

Richard: The fireflies that light up, with a flash or glow when they're adults, that communication signal is actually for their own species and it's for communicating with potential mates. So, either the male saying check me out, check me out, I would be a great mate, or the females kind of just letting males know where they are.

Richard: And in some cases, actually selecting which male that they want to meet with.

Matthew: Yeah, two different species have different flashes. I mean, if they're looking for a mate, they don't get confused, surely.

Richard: Yeah, they do. I've heard some people compare firefly flash patterns to, Morse code patterns. I think another good comparison is to bird songs. So different species are going to have different flash patterns and those are kind of characterized by specific timing. It's almost like a particular rhythm and also by the shape of the flash so that might look like kind of a trembling flicker.

Richard: It could look like an upward moving, swish of light and in some cases, it's going to be kind of a sustained low that just kind of over the forest floor. Yeah, and all the different colors.

Matthew: I mean, I've almost never seen fireflies. At least for light up ones because where I live in Oregon, we're just in the wrong part of the country, but visiting relatives in Chicago, I've seen them there and they were green. And I've seen some photographs that have been more yellow. So presumably color helps communicate to the right species as well, does it?

Richard: Yeah, definitely. I’d say the most common colors are yellowish green and greenish yellow. That's kind of where things tend to concentrate. But you do have a spectrum from green to orange or even kind of slightly reddish.

Richard: And one pattern that you see, quite often, is that the fireflies display at dusk, so a lot of people are familiar with the big dipper firefly in the eastern and southern US. And this is a firefly that will display, before it's truly dark.

Richard: Some people say that they start flashing when you can still read with the last of the daylight. So, fireflies that flash at dusk tend to be much more yellow and that yellow light stands out a lot better against just sort of the light that's reflecting off of green leaves.

Richard: And then once it's later in the evening and it's fully dark, you tend to see the more greenish glows and flashes. So sometimes that's different species and sometimes it's even the same species that will shift its color tone over the over the course of the evening.

Rachel: Oh, that's cool. I didn't realize they could change colors.

Richard: Some of them can, some of them can. The other factor that comes into play is just our, vision. So, probably the people who see Fireflies, most closely to the wavelength that they actually are, are young kids with really great vision and then as age sometimes it's harder to pick up the color or the weather conditions like fog or water vapor in the air can also shift the colors a little bit.

Matthew: Because I guess our eyesight is different from the Fireflies eyesight. So, we must perceive the colors just slightly differently.

Richard: Yeah, more than slightly differently, I think, between us and fireflies, they're not very sensitive to the color red that they can see a little bit and they can also see ultraviolet light which we can't see.

Rachel: So, you talked about, fireflies lighting up at different life stages. So, some light up in the larval stage and those are the glow worms that you're talking about. That we fondly know them as.

Richard: So yeah, glowworm is a very tricky term because it can mean about 4 different things. And one of those things is, a fly larva like in New Zealand. There are these fly larvae in caves that actually produce like a blue light so that's one thing that glow worms can also refer to.

Richard: Kind of a firefly cousin also called the railroad worms. Where the females look pretty warm like and they produce light. But yes, a lot of people will refer to kind of baby fireflies as glow worms because they're wingless and look a little grub like and then the, the fourth thing that, they can refer to is basically a life history type, within the firefly family where, it tends to be just the females that, glow.

Richard: And they don't have wings and they look kind of larvae like, and then the males do have wings and some of them produce light, some don't, but they're kind of flying slowly through the forests or through gardens looking for females.

Richard: An example of that would be like the glow worm in James and the giant peach. Most of the fireflies in Europe are of this glow worm variety. So, the common names for firefly, tend in different European languages, tend to be some variation of things that are worm like rather than things that are fly like.

Rachel: Interesting. So, within these different life stages and you have all these different species of fireflies do all fireflies that light up as adults also glow when they're in the larval stage?

Richard: Yes, so producing light during the larval stage is much more of the rule. We used to say, oh, every single firefly, every member of the family Lampyridae, produces light during the larval stage and then a few years ago, it was a good lesson in not using absolutes.

Richard: Some scientists found a firefly larva on these mountains in South America that weren't producing any light. And the other really wild thing about these firefly larvae is that they were eating, toads.

Richard: So, you have beetle, predating amphibians. So, you know, I'm almost cautious to say, all or none, when, talking about fireflies. But in North America, yes, most, do glow. Including ones that as adults do not produce any light.

Rachel: Okay, and those would probably be the ones like Matthew was saying - I grew up with outside of Portland and that's where he's located. Well, I didn't see fireflies growing up as a kid because we don't have the adults that light up, but we do have fireflies right, in the Pacific Northwest?

Richard: You do, pretty much every state in the continental US has some kind of firefly and in California and in like very southern Oregon you have the California pink glow worm which is this really neat beetle where the females don't have wings and there are these little pink things that will climb up on a rock and glow this greenish light.

Richard: There's also something called the Douglas fir glowworm that you have in the Pacific Northwest. And a lot of people kind of in the late fall will stumble across these, particularly the larva glowing in the leaf litter.

Matthew: I've seen the adult fireflies in my neighborhood. So, I found them both in my kitchen, the first time seeing one, but I've been in the garden also in a local park.

Matthew: I know they don't light up. So, I mean, how do they communicate because if they can't flash to attract a mate, do they have some other warning? Because they're not talking. Or maybe they are just not listening.

Richard: So, it can maybe more of a one-way signal, for these fireflies. So, research was recently done on the winter firefly, which is similar to the daytime fireflies that you have in the Pacific Northwest that used to be in the genus, Ellychnia. Had some little dark beetles with some kind of pink on the headshield. So they're using, chemical signals.

Richard: So, the females will give off, some sort of pheromone or chemical signal and then the males will use their antennae to follow those kind of scent trails through the air and find the females.

Matthew: Yeah, I mean, flashing must be a little bit limited in the distance. You know, because each have to be able to see. Presumably, the pheromones allow them to find each other without being able to see to start with this.

Richard: I think there is some research that suggests that, even in fireflies that produce light, for example, the Blue Ghost firefly, which is the type of glowworm firefly, glowworm in the sense of having flightless, females. They may use, chemical cues at a distance, and then once they're up close, light will like will come into play.

Rachel: And is the light also created from chemicals much like the pheromones?

Richard: It is. So, I'm not the best person to explain the chemistry of it, it's been a long time since I took chemistry class but it is a chemical reaction that produces the light and this reaction isn't unique to fireflies, in any way.

Richard: It's found in a lot of different marine organisms and certain types of mushrooms, other types of beetles like the headlight click beetles. But there's basically two important chemicals, luciferin and luciferase both named for the fallen angel light in the Bible and those chemicals react with oxygen and with ATP, which is the kind of the energy molecule that all organisms use.

Richard: And then there are a few other chemicals that can come into play like calcium and magnesium ions and nitric oxide that kind of help to regulate or like act as a light switch. And the result of that reaction is this light that we see. That's very, very efficient. It produces, basically no heat. As part of that reaction.

Rachel: Well, I think you explained that quite well. Got a lot more than I thought.

Matthew: Yeah, I'm just impressed that the fireflies can control it with such precision that they can flash like Morse code as well. That's great.

Richard: Yeah, it is. It's definitely impressive and, I think one of the ways that they can control it is basically, when they inhale, so to speak, into their abdomen, controlling the flow of oxygen can help regulate that.

Rachel: So, we've talked a lot about light and that's often when we see or think of fireflies and we see them lighting up. But what are fireflies up to when they're not blinking? Because it seems like the season to see fireflies is quite short in the summer. What are they doing the rest of the year?

Richard: Yeah, so most of them most of the year and for most of their lives, fireflies are in the, in the larval stage.

Richard:  If you can't picture what a firefly larva looks like I recommend googling it really quick. Sometimes I've described them as like a roly-poly bug that's gone through a pasta press or a tiny like a tiny pangolin or I've heard people call them dinos like refer to them as dinosaur caterpillars.

Richard: So, there are these really neat, kind of plate covered, protected, larvae, and a good time to see them, if you're in the eastern side of the US, sort of late fall, is to go outside in the evening when the ground is damp like after a light rain is really great. And you can find these, these little specs of light crawling around the ground and fireflies before they become adults they're just eating machines they spend their nights looking for earth worms and snails and slugs and probably a lot of other things that we have not been able to witness them, but soft bodied little invertebrates.

Richard: And they’re these, ferocious little predators. Kind of imagine coming upon a snail that's bigger than you and just shoving your, your head into the snail shell opening and injecting a neurotoxin and then, you know, spending the next few hours slurping pretty digestive snail juice out of the snail shell. Like that's kind of the life of a firefly which does not sound like this magical fairy existence that a lot of people might imagine.

Richard: So, when people think about firefly habitat, it's like, we really need to think about what the larvae need because most of their lives are spent as larva and that's when they need to eat most of their food that's how they need to pass lots of different weather extremes. And yeah, the egg phase is like a couple weeks and the pupae phase.

Richard: So, kind of like a butterfly and like all other beetles, they do kind of full metamorphosis and hunker down as a pupa for a couple of weeks. Sometimes they build those pupae and little kind of igloos. There's a species or a group of species and the people in the eastern US will often find in the very early spring, like when there's still snow on the ground.

Richard: If you walk around and check kind of the south sides of, of tree trunks, you can find larvae that have climbed up the tree trunk and they've attached their sort of tail to the tree bark. And they're just, going to hunker down and pupate there in this totally exposed, spot.

Matthew: The fact that any insect goes through such distinctly different stages in its life. And can be so transformed between. You know it's young and its adult form always intrigues me.

Matthew: I mean, you obviously know a lot about Fireflies. And you must spend some of your time out doing research in natural areas or maybe backyards. What does an evening of firefly research look like.

Richard: Well, it's definitely one of my favorite parts of my job where I've kind of pinched myself when I'm out experiencing something that so many people have such fondness for and can feel like such a kind of transcendent, experience.

Richard: I will say that I'm often kind of in a frantic state because there's so much to take in at once. So, I need to plan my evenings and I need to know kind of when sunset is and then I need to be kind of in place where I think I need to be. Maybe that's half an hour after sunset. Maybe it's exactly at sunset, depending on the species.

Richard: And I have a have a thermometer with me that I, take the air temperature very regularly, because when I'm interpreting their flash patterns,  I use a voice recorder to measure the time distance between individual flashes of an individual firefly.

Richard: And it's really the air temperature that's going to set the tempo, for that or be the calibrator for the rhythm of the fireflies. So, I go back and forth between pulling a voice recorder up to my, up to my face while I kind of count flashes out loud, checking a thermometer, and then I'm often chasing after an individual firefly with an insect net trying not to, you know, get into a thorn patch or, trip and fall.

Richard: And trying to do all of this in as much darkness as possible just you know, either with my headlamp off or, using a dim red light, for just the smallest amount of light possible.

Matthew: Yeah, do people ever come up to you and wonder what you're doing out there?

Richard: They have and they're often like really excited to hear that I'm studying fireflies and they often have something to tell me about something that they've seen, related to these insects.

Matthew: That's good. Because if you're out in a space doing a seemingly odd or suspicious activity that's often when you attract attention.

Richard: Yeah, I actually I wear a reflected vest just so I don't surprise anyone And I try to, you know, get there early enough to let people know what I'm doing before. Before I'm stumbling around in the in the forest with very little light.

Rachel: So, I've heard a lot of people say that they've seen fewer and fewer fireflies compared to years ago. Especially when they were a kid. How are firefly's doing? Do we have any sense of what their populations are and should we be concerned?

Richard: We definitely have reasons to be concerned and some of that just has to do with the patterns that we see with insects overall, where we're seeing in places where we're paying attention, we're often seeing fewer species and lower numbers of the species that we do see.

Richard: But it's not actually a simple answer because we have so many different species of firefly. So just like with say birds or butterflies, some species seem to be doing okay. We see them in lots of different places. Even in suburban areas or even urban areas and they seem to have adapted okay, to all the changes that have happened in their habita

Richard: But there are, a set of species that we’re really concerned about, partly because they were pretty rare to begin with. They live in specialized habitats some of those are on the coast and are vulnerable to sea level rise. Others, maybe live in wet wetlands and dryer habitats. And we really worry about the impacts of drought.

Richard: So, several years ago, the Xerces Society and various partners that we work closely with, did IUCN red list assessments for extinction threat for, a large number of North American firefly species. And about, 1 in 6, species were found to be like definitely, at some risk of extinction. And it's estimated that, up to 1 in 3 species, could be at risk.

Richard: A lot of the species we just didn't know enough about where they occur or what they're baseline population levels are, to kin of, make any sort of chart of what the what the trends are. And again, as with many insect species, we're lucky with a few groups, like some butterflies and some bees to have baseline data from 50 years ago or a hundred years ago.

Richard: But we kind of just need to start now and get as good of data as we can and maybe go back to places where Fireflies were found 100 years ago and see if they're still there. Because, it's not like with some birds for example where we have pretty good data going back 100 years for actual counts.

Matthew: So, it sounds like it's not looking great for many of the fireflies and for a lot of them we just don't know. But from what we do know, can you tell us? What's an impact? I mean, what are the kind of things that are affecting fireflies?

Richard: So, a lot of the things that are affecting other insects are also affecting fireflies. So, habitat loss is a big one, you know, loss to so development or to, kind of large-scale agriculture. Climate change is impacting fireflies in lots of different ways. As I mentioned, kind of sea level rise for coastal species, increased drought or flooding, changes in seasonal timing.

Richard: And then also, thinking about what fireflies eat. You know, again, things like drought, it's not good for, the moisture loving species of firefly. Other things that are impacting fireflies include pesticides whether applied kind of in developed areas or in agricultural areas.

Richard: And then in you know residential settings and then finally light pollution has had a set of negative effects on fireflies as well mostly related to their reproduction and interfering with that courtship communication that they do.

Matthew: Yeah, because when it's brighter, it must be harder for them to see the flashes for example.

Richard: Yeah, exactly, you know, romantic relationship depends on communication and when that communication, you know, breaks down, it's, it's not good. It's kind of like, you know, imagine some sort of great social gathering in a place that suddenly has construction noise at a really high decibel level it's like you know, not going to be the best courtship place.

Rachel: So earlier you mentioned that we just don't really know what the populations are of these various fireflies and excitingly, Xerces and other partners worked together to start the Firefly Atlas.

Rachel: Can you tell us a little bit about that program and how this can help us to protect fireflies?

Richard: Absolutely. Yeah, the Firefly Atlas is, a collaborative initiative that lets people contribute to our knowledge and protection of firefly species across the US and Canada. So, whether you are just a firefly enthusiast who has access to habitat or if you work for a state wildlife agency or maybe you manage a local park.

Richard: here are opportunities, to go out and do a firefly survey, and to document with photos and flash pattern measurements. And a survey protocol that we provide what species you're seeing and roughly in what numbers and we do have a set of focal species that we’re really keen on getting, more information about.

Richard: So those focal regions are the southeast, the mid-Atlantic, and the southwest but if you're in the mid-west or even the Pacific northwest or California, you can still go out and do a survey you'll need to probably do a little more planning and reconnaissance to figure out where and when to do that.

Richard: And the idea is to create a kind of a map and data database of a firefly records that can kind of complement museum specimen collections and that will give us a much better idea of where different species are found, how they seem to be doing, what threats are affecting their habitats.

Richard: And in just, you know, less than 2 years, it's been really exciting to see young people out there doing surveys and contributing to our knowledge. Finding firefly species in states where we didn't know that they occurred and it's really helping I think the state agencies get a better handle on you know, just the basic information of: What species do we have here? Where are they found? Which ones should we be kind of keeping a close eye on? To make sure that they don't decline or blink out.

Matthew: And so, if our listeners wanted to get involved with the Firefly Atlas, how can they sign up?

Richard: So, going to fireflyatlas.org. You can create an account which will then, allow you to, submit data. You can also, sign up for a newsletter and just keep tabs on what's been going on with the Firefly Atlas project.

Richard: And even if for whatever reason doing surveys, isn't going to be possible for you. There are resources where you can create a checklist of species that are found in your state. And read about the different species that are most at risk. There's a lot of just educational resources about fireflies on the website.

Matthew: Yeah, and people who want to help out, they don't need any special background. I mean, if you just want to help, you can just sign up, right?

Richard: They don't. You can sign up there, kind of like with the Bumblebee Atlas projects. There are a few pieces of equipment that you'll want, like a camera and probably an insect net and it does take a fair amount of kind of doing your homework to learn the, the survey protocol. We have some training videos available on the website and then a really important thing too is having really clear communication with whoever's land you're doing the firefly surveys on and following, the, Xerces Society code of conduct for community science.

Rachel: So, you've talked about lots of different things that are impacting fireflies like light pollution and climate change and obviously we've talked about the firefly atlas, but there are 1 or 2 things and simple things that people can do to help fireflies.

Richard: One thing, and this might sound a little strange, just go outside at night. And there are few things that you can do when you do that. One is just sort of like take in, if you have fireflies near you. Spend a little more time watching them and appreciating them and, you know, if you're doing that with someone else in your community it can bring so much joy. That is my first suggestion is like tap into that joy and that like sense of sense of awe.

Richard: The other thing that you'll notice we need to do outside at night is there may be things that are interfering with your enjoyment of fireflies and sometimes that is you know a light post or other outdoor lighting.

Richard: And you know, even if you don't have a garden that's supporting a firefly habitat, you can find out more about your town or your states outdoor lighting kind of regulations and best practices and you can encourage your local government to take wildlife into consideration when doing planning of outdoor lighting.

Richard: And then I'm probably going over here too many things, but the third thing I would say is be curious about how pesticides are being used in your community. So that might be neighbors following kind of more insect friendly mosquito management practices, or maybe it's how your local community government is responding to mosquitoes and just making sure that they're following the best practices for balancing public health, and protecting wildlife and insects including fireflies.

Matthew: That's great. I love your first piece of advice, getting people to go out and just enjoy is such a such a great thing.

Richard: Yeah, I think a lot of people say, oh, I don't see fireflies anymore. I think declines and local extinctions of fireflies are part of that but part of it is also people not going outside at night as much. And when we find fireflies, you know, we're going to be most excited about protecting fireflies when we know that they're there in our communities and we're enjoying and valuing them.

Rachel: Definitely. Well, we're going to end here on my favorite question. And that is what inspired you to work with fireflies.

Richard: I mean, how could I not work with fireflies? I'll say that I had the opportunity, several years ago before I joined Xerces Society to work with, volunteers at a national park in South Carolina, Congaree National Park, to collect some data on the synchronizing firefly, and I just, you know, got hooked to, again, be out at night.

Richard: Both enjoying this beautiful site, and protecting biodiversity is just, what a combination you know.

Rachel: Well, thank you so much, Richard. It was great talking with you and learning more about these incredible insects. It was really great to have you here.

Richard: Thank you for having me on.

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Rachel: If you’re already a donor, thank you so much. If you want to support our work go to xerces.org/donate. For information about this podcast and show notes go to xerces.org/bugbanter.