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February 19, 2024

43 Minutes

Guests: Dr. Avalon Owens

Tags: endangered species, fireflies, special guests, habitat,

Light pollution. Go outside at night and you’ll notice it — lights on buildings, in gardens, along streets, glowing on the horizon. It might not seem like much, but this is changing the world for animals that rely on darkness. Imagine evolving for millions of years with only the stars and moon and now being faced with a landscape full of additional light. What happens to insects when the night is full of light? Can fireflies coexist in urban areas? Are there things we can do to reduce our impact?

Guest Information

Dr. Avalon Owens joins us from the Rowland Institute at Harvard. Avalon received her Ph.D. in biology from Tufts University in spring 2022, where she studied the impact of artificial light on bioluminescent fireflies. She also holds a B.A. in integrative biology from Harvard University and an M.S. in entomology from National Taiwan University.

Show Notes & Links

In this episode, we talk about insects that are active at night and how artificial light affects them. We talk about why insects are drawn to artificial light. Lastly, we talk about how we can reduce our impact on night-active insects.


Rachel: Welcome to bug banter with the Xerces Society where we explore the world of invertebrates and how to help these extraordinary animals. If you want to support our work go to

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

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

Matthew: Light pollution. Go outside at night and you’ll notice them — lights on buildings, in gardens, along streets, glowing on the horizon. It might not seem like much, but this is changing the world for animals that rely on darkness. Imagine evolving for millions of years with only the stars and moon and now being faced with a landscape full of additional light.

Matthew: What happens to insects when the night is full of light? Can fireflies coexist in urban areas? Are there things we can do to reduce our impact?

Matthew: Joining us today to talk about these and questions is Dr. Avalon Owens from the Rowland Institute at Harvard. Avalon received her Ph.D. in Biology from Tufts University in spring 2022, where she studied the impact of artificial light on bioluminescent fireflies. She also holds a B.A. in Integrative Biology from Harvard University and an M.S. in Entomology from National Taiwan University.

Matthew: Welcome Avalon! We are thrilled to have you here — our first non-Xerces guest!

Avalon: Yes. Thank you so much. I'm thrilled to be here. So honored to be the first.

Rachel: We're really excited to pick your brain and to learn more about light pollution. Especially from someone who has studied it.

Avalon: Yeah, of course.

Rachel: So, before we get into light pollution in your research, can you tell us about nighttime insects? I think fireflies and moths. They're the most obvious and probably the most commonly thought of, but are there other insects that are active at night?

Avalon: Yes. I think this is huge. So much of the discussion is around light pollution, insects, and insect conservation. Humans bring a lot of our own biases to the table.

Avalon: This is something I'm sure you guys are familiar with. Insects, they're very small and so we don't really know what's going on with them. Similarly, humans, we hang out outside during the day. Not a lot of people go outside at night.

Avalon: And so, we have this bias where we think everything important is happening during the day. And this just couldn't be farther from the truth. Most insects, so over 50% of insects are active at night. And we have these classic examples.

Avalon: Fireflies and moths are those we are more likely to encounter. But all sorts of insects. You might be familiar with the honeybee. Well, there are other bees that are active at night. There are different species, but they are doing similar things at night.

Avalon: Bumble bees as well. There are ants, dung beetles, all of the insects we're used to thinking about. Many of them will either be partly or entirely active at night. And as you know, as we continue to learn about the natural world.

Avalon: We'll find even more species active at night because we just don't do as much research on nocturnal insect biodiversity. On top of that, with climate change and human change of the environment, the addition of lights, etc, and increases in temperature as a result of climate change, a lot of things are becoming more nocturnal over time because it's cooler at night.

Avalon: And there are fewer people around. And so, the nocturnal niche is sort of getting invaded by a lot of things at once, including some insects. There's a lot out there. It's not all fireflies and moths.

Avalon: And for them, light pollution is a totally transformative thing that we're doing to their world.

Rachel: Over 50%. I didn't know that. Wow.

Avalon: Yeah, well over 50% of the 24-hour cycle is dark, right? It kind of makes sense, right? And there are a lot of reasons to go out at night. So originally, I think most animals started doing it as a way of avoiding predation.

Avalon: So, it's maybe easier to get around during the day. You can see more, it's a bit warmer, but there are a lot of things that want to eat you and so the night becomes this safe dark place where if you can thrive, you can do really well and it has expanded from there.

Matthew: You mentioned dung beetles and that made me remember some research I read one time, where the research has figured out that the dung beetles were navigating by the Milky Way. And they put little visors on the top of the beetle's head so they couldn't see the sky. Then they went in the wrong direction.

Avalon: So, I think dung beetles are a really great example because, when you learn about them in textbooks, it's like the savannah and it's really sunny out and they're rolling their ball of dung, right?

Avalon: But within a single genus of dung beetles, you actually have multiple species that are sort of stratified to different parts of the day.

Avalon: So, you'll have your ones that are active during the day and then some that come out right at sunset, and then there's some that come out right at night and they are sort of adapted in different ways to these lifestyles and it's how many species can coexist in the same area by using different parts of time in a way.

Avalon: And the ones that are nocturnal, they use the stars or the Milky Way or visual signals in the sky overhead as landmarks to guide them when they're sort of scooting their balls of dung. In their case, they just want to go straight so they can get away from the rest of their competitors as quickly as possible.

Avalon: It's incredible, right? You can look up videos of this. They’ll make their ball of dung and then they climb up onto it and they twirl around and they are looking up at the sky, taking stock. Then they decide, to climb back down, and off they go.

Avalon: You know, it's incredible behavior that relies on having pristine night skies as it happened.

Matthew: Yeah, totally. So, what is insect vision like? I mean, how do insects, fireflies say, see the world?

Avalon: Insect vision is pretty hugely diverse. And it's also kind of modular in this cool way in that a particular insect species is likely to have vision that's very adapted to the things it needs to do, more than I would say vertebrates.

Avalon: We have sort of general-purpose vision. There are lots of tasks that we are capable of completing. So, fireflies as an example, they're really nocturnal. So, number one, they have to be very, very sensitive to light.

Avalon: They have these big eyes that can take in a lot of light. And that comes with a few trade-offs so they also see things a bit more slowly if that makes sense. So, in terms of say frames per second, generally it takes them a longer amount of time, a longer fraction of a second to collect enough light so that they can form a picture.

Avalon: So, they see things kind of slowly and they also see things as kind of blurry too. Human bias once again, we imagine insects are seeing the way we see and we can resolve so many details of our environment. But a lot of insects, especially nocturnal ones are just trying to get as much light as possible.

Avalon: It'll be sort of blurry around the edges and they're not really able to make out details the way we can. And then the big one is that they also have more limited color vision. Fireflies in particular. Fireflies are essentially interested in seeing one thing and that is other fireflies.

Avalon: And so, they're really good at seeing the green color of others of their species. They can also see UV, which we could talk about why that is, but it's probably useful in some way. But that's it. And their main thing is they have a green photo receptor and they use that to see other fireflies and that's all that they need.

Avalon: However, other nocturnal animals, including moths, some of them have a greater capacity for color vision at night. They're actually better than us at seeing color at night. We have red, green, and blue cones. These moths have UV, green, and blue. That's the wrong order, but you see blue and green. And they can use those to tell the color of a flower under moonlight when for us if we were fully dark adapted everything would be black and white.

Avalon: So, an incredible capacity for vision at night, which comes with some trade-offs, all of which are designed around, you know, accomplishing your goals under really limiting light conditions.

Rachel: Interesting. So, it's important to have that darkness because they wouldn't be able to use these adaptations. It would kind of throw everything off essentially.

Avalon: It throws everything off. So, when you light up a space, all of a sudden, some of this is speculative but let me speculate. All of these day-active insects that are super good at seeing under bright light, you know, all of a sudden, they have a huge advantage.

Avalon: There's a really cool study about, I'm going to say it's a bumblebee. I hope this is true in the tropics where they have switched to a more nocturnal lifestyle to avoid predation or competition for resources, I think probably competition.

Avalon: And the researchers were asking, how do they accomplish this? They have the basic Bumble bee, which is not historically very good at seeing in the dark, they're a bit smaller than moth eyes or firefly eyes.

Avalon: So, how do they manage it? They did a bunch of studies on how fast they see, how many frames per second, how blurry is it, this and that, and ultimately concluded, that one of the ways they manage is they're just not very good.

Avalon: So, they'll hit things a lot, they'll bump off surfaces, and it takes them a couple of times to find their nests because their reaction time is not quite right.

Avalon: However, if you light up the space all of a sudden, it's enough for a lot of animals to get by and then there's a lot more competition, and then the poor firefly that spent millions of years getting super-sensitive eyes is just totally blinded and meanwhile everything else is more able to cope, including humans.

Avalon: That's why we light it up, right? We wanted to make the night more pleasant for a day active animal.

Rachel: Yeah, and you talked about one of the purposes of fireflies lighting up like their one job is to see other fireflies so that they can mate and communicate. And if that's taken away because of this artificial light that is now there in the darkness, how does a species survive that?

Rachel: I mean we're going to get more into this but it's just so important I think we've laid the framework that these animals are adapted to be living at night for very good reasons. And they need the darkness. That's like the key is that they need the darkness.

Avalon: Yeah. 100%. And I think you mentioned it a little in the introduction, but I cannot overstate, you know, for all of evolutionary history the night has been totally dark and so what we're doing to it is unprecedented.

Avalon: These animals are not prepared to cope with change of this kind and many of the other things we point to as drivers of insect decline. They have evolutionary analogs. So, climate change is happening much more rapidly than it ever has before, but temperature fluctuations are within the realm of an insect's life already.

Avalon: They have the ability to adapt to a certain extent. And even pesticides, you know, a lot of them are based on plant defenses or other chemicals that insects have evolved to cope with to varying degrees.

Avalon: And so, you see things like pesticide resistance utilizing the genetic tools that the insects have to face threats but there has never been a street light. So, oh, the poor fireflies, right? They had no way of knowing this would happen. Along with moths and other insects.

Matthew: Yeah, I know in the introduction we refer to it just as light pollution. But scientists like yourself who study it have a more specific name for this kind of nighttime lightning. Can you tell us what that is and how you define it?

Avalon: Yeah, so our jargon of choice is artificial light at night or ALAN, and there are some key reasons that we talk about it this way. So light pollution, this term is quite old actually. I mean, relatively speaking, and has been used a lot by astronomers, but also city planners.

Avalon: Light pollution is any light that is wasted. And so, it's a very human definition. We're assuming the light has a purpose, but if you get glare, like when you're driving in the car headlights make it hard to see, this is wasted light.

Avalon: It's not helping people, it's hurting people, and therefore it's pollution. And similarly, if you're street light lights up the sidewalk, but also part of the lawn where nobody should be walking anyway, this is wasted light. This is light pollution, because you're wasting money and you're not accomplishing your goals.

Avalon: So, from an ecological perspective, all light is pollution to insects. They don't need it. They don't want it. And so, I like to speak about it more generally as artificial light, but the other thing is it has to be at night because that's when it does the most damage.

Avalon: And also, you know, to take the scientific view, we have to be a little more objective. Pollution is a loaded term. I have no opinions about whether it is good or bad. I simply want to know how the insect responds to it. So that's another reason we talk that way.

Matthew: Yeah, it is really good to have defined it like that. I know that term and I use it like that. I know that term and I use ALAN, but I hadn't thought of it as pollution being waste.

Matthew: And therefore, this shift of the definition. I should also tell people that if we complain about ALAN, it's not personal, right?

Avalon: Sorry to all the Alan's out there. Yeah.

Rachel: So, I am excited to ask you this question. Can you tell us about your research? How did you go about understanding insect’s reaction to different light?

Avalon: Yeah, so I'll talk about my work on fireflies, which more or less I have a complete package there. There's other stuff we can talk about later with moths that I'm kind of still working on.

Avalon: But, for my PhD research, I sort of wanted to get the full picture of what artificial light is doing to the local fireflies around New England.

Avalon: And that can mean so many things, which is why it's such a great thesis topic, right? An insect lifecycle is very complex and there are many different ways that artificial light can interfere with this.

Avalon: And so, my idea was to take a whole lifecycle approach. This comes from a conservation perspective, right? So, the whole life cycle matters. A firefly has to get all the way from egg to adult to more eggs in order to make more fireflies and this is what we want, right?

Avalon: And so, I did a few things in the lab rearing fireflies under different light conditions and seeing how they did, looking at how they move also because you can put a light in a backyard and all the fireflies might disappear, but does that mean that they have died?

Avalon: Does it mean they're somewhere else? Movement is a big part of this. And there's some interesting stuff there as well. But the bread and butter, and I think the most fun thing to talk about on a podcast, is my work on firefly courtship and reproduction.

Avalon: So, the final stage, once the firefly has gotten all the way past one to two years of vulnerable development, which, you know, is no joke. Most of their time is spent as a larva. But assuming they've gotten past that, they pupated, they've come out, they're adult fireflies flying around.

Avalon: These are the ones we know, the ones we love. They're only alive for like 2 to 3 weeks. During that time, how does light affect their ability to find dates, go on dates, have a good date, and lay eggs and to make more fireflies.

Avalon: And so, I've looked at this in quite a few ways. Usually focusing on not only the effect of light itself, but various kinds of light. And for a long time, I was thinking a lot about color. So different colors of LED light at different brightness.

Avalon: How does that affect firefly courtship, which is when the male and the female firefly are flashing back and forth? I guess you guys did a podcast about fireflies. So, you're all experts and I don't need to explain.

Avalon: But yeah, but the fireflies flashing back and forth is an essential precursor to mating. If they don't have a nice date, they're not going to mate at the end of the night. So, looking at how in the lab and in the field, we would find pairs of fireflies that were chatting happily, put a light on overhead and see what they did.

Avalon: And I had a very interesting realization quite early on, which has to do a little bit with, again, human bias and how we see things. So there had been people before who had gone out into a field and put a light up and they had shown that the display, the firefly display as a thing, all the flashing activity, it would decrease a little bit.

Avalon: Maybe, I'm going to say around 50%, so they would flash about half as much. Okay, so that seems bad, right? But it could actually be worse and it is in fact worse because the firefly display is made up of male fireflies flying around doing their courtship advertisements.

Avalon: So, they're telling all the ladies who are on the ground how great they are and how much better they are than the guy that's flying a couple feet to the left. And then on the ground in the grass, the female fireflies watch this display just like we do, and whenever they see a male that they like, they'll flash back and the two enter this dialogue.

Avalon: And so, when we look at the effect of light on the firefly display as a whole, we're only looking at the male behavior. How do the males respond? And in terms of firefly conservation, AKA firefly reproduction, what the males are doing doesn't really make a huge difference because there's a lot of them, they're sort of disposable usually.

Avalon: The female will only mate once per night. She's got a lot of guys to choose from and it's what she decides to do that ultimately determines whether or not we're going to have fireflies next year. And it turned out in the lab and in the field that although the males would flash less when there was a light overhead, the females would go almost totally dark.

Avalon: So, they were much, much more sensitive than the males. Which, not to anthropomorphize too much, but it kind of makes sense if you think of it in terms of, the female is picking whichever guy she likes and she, you know, she's alive for a while.

Avalon: She wants to make a good choice for her eggs. And so, she can afford if there's a light overhead, the vibe isn't right. She'll just sort of decide, I'd rather not. Meanwhile, the males, they're pretty desperate, right? All they have to do is find a mate.

Avalon: They'll mate with pretty much anybody who flashes back at them including me using a PIN light, they'll land and try to mate or the predatory fireflies in New England which we could get into, they attract male fireflies and eat them. So, males will attempt to mate with anything including an LED, and their top predator.

Rachel: Oh gosh, it's tough. What a tough life.

Avalon: Yeah, so, it's a little awkward and embarrassing. So the fact that they stop flashing even a little is significant but they're going to keep trying no matter what.

Avalon: And so, they are really giving us a false impression of how bad it is. Because if the males keep flashing, but the females go dark, you might look at that spot and say, probably the fireflies will be OK. But next year you're not going to see any because the females just sort of dipped out.

Rachel: It's so interesting. So obviously, ALAN interferes with insect behavior, whether it's mating or navigation. Observing the different lights that are out there, there's different colors that are just different brightnesses.

Rachel: Do these different colors or brightnesses impact insects in a different way? Are there some that are better than others?

Avalon: Yes, oh yes, thank you. This is the other part of the whole reason I did all that research.

Avalon: Yeah, I think to a certain extent, I've sort of moved away from thinking this way because of human bias, it just feels like a very human desire, if we could only find the right tool for this situation, we can fix it.

Avalon: It is true that a lot of insects are not very good at seeing red and humans are pretty good at seeing red. And so, and that is sort of true in terms of probability, so anything kind of close to red is going to be better than anything pretty far from red. So, amber or orange light is better than green light, which is better than blue light, which is better than UV light, which is the most attractive.

Avalon: So, it's generally true that we say longer wavelengths like the warmer colored lights are less visible to more things. However, there's never going to be a color of light that only humans can see and nothing else can see.

Avalon: Because we live in an ecosystem and humans, we're special but we are just like animals you know like anybody else. So, for insects specifically, I think red light is pretty good. Unfortunately, people don't like red light very much.

Avalon: They tend to prefer something more like amber or yellow. And for fireflies, specifically yellow light is quite bad because it looks just like a firefly, green or yellow, so there's that overlap fireflies, they have their big green photo receptor which they're only using to see other fireflies and so anything that's similar enough to green is going to have the biggest impact on that courtship and reproduction. And that's unfortunate because fireflies are also really good ambassadors for environmentally friendly lighting.

Avalon: And so, if you like dark skies. Oh, the dark sky people say use amber lights and as you put let amber lights within the fireflies it's like kind of a mess and that's one reason I've moved away from that thinking this way.

Avalon: And brightness too. It's not obvious to me that a dimmer light is actually better because insects’ eyes adjust just like ours do. And so, it's actually an open area of research, I would say. But one thing that's certainly clear is that there are much easier solutions to this problem that are uniformly good and the number one I would say is motion detectors.

Avalon: If people are there, have as many lights as you want. If people aren't there, we should not have lights. Light pollution, by definition, and how could anybody argue against such a common-sense solution? I mean, people can, but they shouldn't.

Avalon: And then like number 2 is curtains. I really feel like lights from houses go out into the environment, especially in some of the semi-natural areas where I do fieldwork. They have a very big impact.

Avalon: And then, dimmers are a good solution as well. So, good for fireflies, because when they're active is usually when people are out, but for things active at like 3 am, no human, I mean some humans, but very few humans are out at 3 am. We could probably turn out a lot of lights at that time.

Matthew: We're talking about lighting here and I know now there's been this kind of move towards low energy, LED lighting and so on.

Matthew: I mean, in our neighborhood, they've come through in recent years and gradually swapped out the old yellow lights for LEDs and they're brighter and some people like them and some people think this is just too bright.

Matthew: It just seems like that's a technology change and maybe an environmental benefit and yet we don't want to kind of demonize that.

Avalon: So yeah, I am actually an LED advocate. I think LEDs are great even though they're doing so much damage, but it's not their fault, they're too powerful. And especially when they were first produced, they were just super, super bright. They can be made as dim as you would like. But we just don't think this way.

Avalon: As people, we think the big number is good like there are 2 flashlights for sale, one says 10,000, one says 20,000. I'll buy the 20,000 because it's a big number, right? We don't often think about ceilings on how bright something should be.

Avalon: I think this also explains why car headlights are so bright these days. People buying cars, you're choosing between headlights. Well, I want to see better. But this leads to this rising tide effect where now the old lighting looks really dark in comparison to the new LEDs and so you need to increase that, and so it's a human behavior issue, not a technology issue, and LEDs are super energy efficient.

Avalon: This means that people leave them on all the time because it's very cheap to do so but ultimately it is good for the earth to switch away from older lighting types because of the carbon emissions associated. I mean, lighting is one of the main uses of electricity municipally.

Avalon: It’s just one of the big ways that we spend our money. So, I think LEDs are here to stay. They can be made dimmer. They can be made different colors. And importantly, they can also be linked with smart devices to motion detectors and sensors of different kinds to make them really work for us instead of against us, but it does take a little bit. You as an individual can only do so much and it's a community effort.

Avalon: It often is best on the local level to work with your neighbors and say, we all want to lower the amount of light. Have a better night sky, have a better nocturnal ecosystem. And then you will be surprised at how much you can see under quite dim light. It's all relative. You know?

Rachel: I was just thinking, I get really frustrated when my partner uses his phone when I'm sleeping. I'm so sensitive to light and I was just thinking if I was an insect outside and I couldn't find the dark space I'd be so mad. I'd be so annoyed but, I can just turn the lights off.

Avalon: So, they don't have curtains, they don't even have eyelids for goodness sake, what is an insect to do?

Avalon: We make it really hard for them and we don't have to.

Matthew: Yeah, I'm going to ask a really silly question now, but when you talk about light and insects, what everybody thinks about, is there an easy answer to why moths end up doing that?

Avalon: It's not a silly question at all. It's my favorite question. It is surprisingly difficult. You would think this is something that we've known that moths do for thousands of years. Ancient Roman beekeepers would use flames near their hives to get the moths to control wax moths, so they would use fire as a pest control method.

Avalon: So, we've known that they do this for so long. Why did they do this? Such a good question.

Avalon: There are many theories, and I don't think any of them really paints a full picture. And I also think, human bias once again, we tend to view flight to light behavior as one thing because we see it, they're either at the light or they're not, and we categorize it in our mind this way.

Avalon: But, there's many reasons that you might go towards light, so I think to some extent all of the theories are true. So, one like that is the dung beetles. So, the dung beetle using the Milky Way as a landmark.

Avalon: It's trying to say, okay, there's some sort of distant thing. And if I follow the line of the Milky Way or if I keep the Milky Way pointed to my right, that will help me keep a straight line.

Avalon: And so similarly, many moths, especially migratory ones, may use the moon as a landmark and either fly straight towards it or put it to their right, or put it to their left. This works fine when the light source is at an infinite distance, like the Milky Way or the moon, but if it's a street light, if you sort of keep it on your right, you will actually end up spiraling into it because you will get there.

Avalon: You were not expecting it to be actually achievable so then the moth gets there and then it's like the dog that is chasing the car catches the car like what do you do? And so at that point when they're close to the light there could be a lot of other things going on, so a lot of lights are hot and that might interrupt their flight behavior in some way.

Avalon: And there's also a new study. So active research is still happening. A new preprint came out only a few months ago, positing that part of the reason that moths will swarm around lights and look as if they're unable to escape, is because they actually don't know which way gravity is.

Avalon: They're so small that they can't feel it. And this makes sense. Insects generally are quite small. And so, the way that they've figured out knowing which way is up and which way is down is by keeping the light half of their eyeball overhead because the sky is light and the ground is dark, usually. And at night this has also has been the case for millions of years, right?

Avalon: The sky is bright with stars, the ground is dark with shadow, etc. But if you're next to a light, all of the sudden the bright side is over to your left or to your right and then just like a plane that sort of loses control, if they're flying against gravity, they get all confused. So, that's a possible reason. And then there are other theories about, is there something about the light itself that's super attractive like the insects want to go to it itself?

Avalon: And UV lights are most attractive to insects. So, the question naturally is, why is that? What is it that they like? And I think this theory has fallen by the wayside in recent years, but I feel like it needs some love because it's certainly true.

Avalon: From my experience, if you have a house fly in your house, it'll usually fly at the windows and it's because it wants to get out. So, a lot of insects will fly to light spaces because they want to escape in some way. And I think their vision is super blurry right, they don't know that a street light is not like a window, they don't know a lot.

Avalon: They're doing their best. So, they might be trying to get to the light itself because they think it's something good. But it's not.

Rachel: So, I just have kind of an odd question, but are there any insects that are benefiting from ALAN?

Avalon: I think, I think yes, maybe speculative, but I'm going to speculate freely. It's like so many things. It's an environmental disturbance that sort of shakes everything up.

Avalon: And so, one thing that you'll often see is moths, mosquitoes, gnats, other insects will fly to light. And then predatory insects will sort of come behind and be like well this looks like a good place to have a snack.

Avalon: So, ground beetles will forage at night. A lot of spiders do this as well. And so, they're sort of exploiting this behavior. What is the ultimate outcome? Not sure about that one. I mean, in a way, in theory, these like predation, predator prey relationships should be self-balancing in some way.

Avalon: Fireflies is an interesting one. With the dung beetles, we talked about with its own little niche of time. Because light pollution often creates an eternal twilight. Those animals that have evolved to be active during twilight, all of a sudden, their habitat is twice as big, right?

Avalon: It used to be 30 min around sunset and now with all the lighting it's like an hour and so I do think that those species might be doing pretty well. They can get more done, and they are just totally primed to take advantage of these varying light levels.

Avalon: And with fireflies, I have some reason to think that some of them are taking advantage of this. So, the most common firefly in the US, Photinus pyralis, is also pretty dusk active, active around sunset, and really likes suburban lawns. You'll even see them flying around Central Park in New York City.

Avalon: So, they're quite urban little fireflies and they are moving upwards every year with climate change. They seem to be doing pretty well. And frustratingly, just like the flash display situation, it's very misleading because if you see a firefly in Central Park you're like that is great fireflies are doing amazing.

Avalon: Most people don't even know that there's more than one species and so they think everything's fine, but there are all of these rare, more delicate nocturnal species that are probably being pushed out, and in fact from my personal experience the fireflies I see around Boston versus you know outer more and western mass.

Avalon: The fireflies around here are a lot more dusk active. They're kind of the same few guys that are active more at sunset. And so, you know to be determined. I guess I can't say anything definitively, but it makes sense to me that we are seeing this loss of pure nocturnal diversity, much of which is already hugely under appreciated.

Avalon: Much of which we probably won't even notice once it's gone.

Rachel: When you see an abundance of one that's not necessarily a good thing because we're losing that overall diversity.

Avalon: Exactly. So, if there's one thing I could hope people would take away from my work, my legacy, it would be that there is more than one kind of firefly and they are all different, and unique, and special. We need to care about all of them, not just the one that's most common.

Matthew: Good. So how can we care about them? I mean, what are other things that we can do to offset ALAN.

Avalon: I think there is so much low hanging fruit when it comes to light pollution. Unlike many of the things that we're doing to the earth, this is a problem that we can solve.

Avalon: There are no residual effects of light pollution. So, when you turn out a light, the problem goes away instantly. And it saves money to do so. So, the only thing we have to do, the small thing we have to do is change people's opinions and make them see it as a problem.

Avalon: Most people just haven't really thought about it before it is human bias. You go to sleep at night. It's not a big deal. Maybe you don't like light from phones, but otherwise you're not thinking about it. Even I think a lot of the insect decline literature, we have so many entomologists that are going out to these sites and they're seeing fewer things and feeling this change in it is a really personal way. And I bet a lot of these people have never been to these places at night.

Avalon: They don't even know what they look like at night. And so light pollution doesn't often come up as a cause of declines because we're just not thinking about it.

Avalon: To get back to your question, I think turning out lights that aren't needed is the biggest one and purely aesthetic lighting, especially in the summer months when most insects are active. I do not recommend- people ever need to feel unsafe.

Avalon: But, you know, the luxury of aesthetic lighting, especially not, we're not like talking about like downtown Boston, kind of a lost cause in terms of light pollution, but vacation homes, beautiful forest retreats in Maine and Pennsylvania. These are some of the worst offenders in my mind because it's some of the only light around and it is pure luxury.

Avalon: I just like my house to look nice or, universities that light up buildings’ facade lighting. You really can't justify that in my opinion, especially if you care about biodiversity and conservation. So, as long as you're out there using the light, I think it's fine. Otherwise, turn it off or put it on a motion detector.

Matthew: So, sounds like it's a fairly simple solution.

Avalon: Fairly simple and yet, you know, it also requires a little bit of persuasion, I think.

Avalon: But fireflies are great ambassadors for this. I've been really encouraged. People want fireflies by their houses. They want to have this experience for them and their children. And I want that too. So, I think it can be done and I think turning out the lights really helps.

Rachel: Well, this has been so informative. I've learned so much and I've so enjoyed hearing about your research and about the things that we can do to help fireflies. We're going to end here with my favorite question is what inspired you to study the impacts of artificial light and insects?

Avalon: Great question. I actually got into this through fireflies and I don't have a beautiful story about catching fireflies as a kid. I'm from Idaho. There are fireflies there, but I had no idea. They're not super common.

Avalon: But I just fell in love with insects after I came to the East Coast. I saw my first fireflies while I was an undergrad. I thought it was amazing. And then during my masters, there was an opportunity. There was a lot of funding in Taiwan for firefly conservation because of the great connection that people there have to fireflies and firefly tourism is a very big industry.

Avalon: And that sort of the moment that it got started as my advisor just asked, do you want to work on fireflies or bees? And I love bees. It's actually the wrong audience for this joke, but I was like, obviously fireflies. They’re so cool. That project was not actually conservation per se.

Avalon: It was sort of an interesting question about how insects live in the city. So, we know that birds in the city sing louder because it's very noisy. And so, the question was, do fireflies flash brighter because it's so bright outside? And it took me in a lot of weird directions.

Avalon: I won't get into it, but the answer is yes, to a certain extent, they will compete with our lights as long as within a certain range. When you turn on an overhead light they'll try a little bit harder to be seen.

Avalon: What that range is and how effective that adaptation is, it's not the full story, but there's something about it that's so inspiring that I just, had to continue to pursue these questions and it's something I really believe in and something that really motivates me. I do think, fireflies, will be okay if we do the right stuff.

Avalon: Xerces has been really so great for this with the firefly conservation that you guys are doing. And light pollution too, this is a problem we can solve. So, it feels good to be able to make a difference in some small way.

Avalon: I do hear a lot of anecdotes of folks saying like there are so many more fireflies when I was a kid, where are they going?

Avalon: I think people are starting to pay attention, and I'm glad there are people like you out there doing this research because it's so important for us to understand their biology and their behavior for us to know what to do, and how we're impacting them. So, thank you for your super important work. And thank you for being here today and answering these questions.

Rachel: It was really, really wonderful. It was such an honor to have you and yeah, you were the perfect first non-Xerces guest.

Avalon: The honor is all mine. I'm hugely delighted and I will come back any time.

Rachel: I have more questions, so we will definitely have you back. Well, thank you so much.

Matthew: Bug Banter is brought to you by the Xerces Society, a donor supported non-profit that works to protect insects and other invertebrates – the life that sustains us.

Matthew: If you’re already a donor, thank you so much. If you want to support our work go to For information about this podcast and show notes go to