Decoding the Language of Fireflies

JESSICA WARE (Curator, Division of Invertebrate Zoology): Ooh, there's multiple of them! That is kind of magical. The first firefly flash of the season. Maybe it just reminds you of summer. Just the magic that you could produce light. This animal is flying and it's producing light. I would say, like, for me, evolution's always remarkable, but it's not how they flash. Right. It's why that's so fascinating. Different species of fireflies—they each speak their own language. Kind of like a language of love.

JULIANA CHAUCA (Hudson Valley Firefly Project Researcher): I think it wasn't till I realized how unique these creatures are that I began looking more into them. I think fireflies are- Fireflies belong to my heart. That's it.

[TEXT ON SCREEN: Roosevelt Island, New York City]

WARE: I'm here in a New York City community garden with Juliana Chauca, an amazing high school researcher working on a community science project about fireflies and whether they may be disappearing from our summer nights.

CHAUCA: I just realized that I see fireflies all the time, but I didn't really hear much about how we could possibly possibly be affecting them. So I thought it would be really interesting to study them.

WARE: In many parts of the United States, especially the eastern and southern states, you can see fireflies on summer nights and you can kind of see them sparkling because over millions of years, they've evolved the ability to control a really precise chemical reaction in their butts. That biochemical reaction releases energy in the form of light and pow, we've got flashes. Those flashes are basically what we talk about when we mean firefly communication. But the question is, what are they talking about?

[TEXT ON SCREEN: American Museum of Natural History - Insectarium]

WARE: I mean, I'm a safe friend, but not all people with insect nets are gonna let you live, pal.

[TEXT ON SCREEN: Jessica Ware, Ph.D. | Curator, American Museum of Natural History]

WARE: My name is Dr. Jessica Ware, and I'm an invertebrate zoologist or entomologist at the American Museum of Natural History. I am a curator and what I do is I study insect evolution. Come on in.

DIRECTOR: So, Jessica, tell us where we are.

WARE: This is where I work. It's a collection room.

[TEXT ON SCREEN: Entomology Department, American Museum of Natural History]

WARE: A reference libraries for insects. Do you want to look at some fireflies up close?

DIRECTOR: Are fireflies actually flies?

WARE: They're not flies. They're not bugs. Some people call them lightning bugs. They're not bugs. People didn't do a great job giving common names to insects, I would say. There's a lot of ones that have kind of misleading names. Fireflies are a kind of beetle. And beetles, unlike flies or like true bugs, have hard wing covers and chewing mouthparts.

DIRECTOR: Are there are a lot of beetles out there?

WARE: There's more beetles than there is pretty much anything else on earth. I think about 25% of the world's species are actually beetles.

DIRECTOR: Everything is beetle.

WARE: Everything is beetle. If you were to come and land on the planet for the first time and you didn't know who was running things, you probably would think it was a beetle.

WARE: The fireflies are in here. They're in the family Lampyridae.

DIRECTOR: All right, well, let's go see some Lampyridae.

WARE:
All right. See how the name just rolls off your tongue? Lampyridae. I actually don't- I'm not great with Greek and Latin, although I did take Latin at school, but Jessica eat discipulus malus. I was a bad student. So, here they are. So there's lots of different species of fireflies. And I think, like often when we say ants, we think that there's just one kind of ant, right? And when we say mosquito, we think that there's just one kind of mosquito. But actually, there's thousands of species. And it's the same is true for fireflies. So there's over 2000 species of fireflies globally, and there's only like 6500 species of mammals. So there's a lot of firefly species out there, relatively speaking.

DIRECTOR: Okay, but these are all kind of similar to me. How do species tell one another apart?

WARE: Ah, but this is where the flashing comes in. You can't really see it here in the drawer, but each one of these species has a distinctive flavor of twinkle.

DIRECTOR: Do all fireflies flash?

WARE: So, not all fireflies flash. A lot of them do. And what's neat is at their juvenile stage the larvae, most of them glow. And why do they glow, you might wonder. Well, that's a very good question. Of course. We don't have time travel to go back to the origin of fireflies. But what we know is that firefly larvae probably tastes pretty growth to predators. So perhaps being glowing, you know, would have signaled I'm distasteful, don't eat me.

DIRECTOR: Okay. So if that's the larvae, why are the adult fireflies blinking?

WARE: Why they do it is a really interesting question, because fireflies are using their sexual signaling—these flashing patterns—to find mates of the same species. Firefly species each have their own love language, right? That chemical reaction can produce different types of color. It can be kind of greenish color, can be kind of an orange-y color, kind of a yellow-y color. And then the patterns of the flashes are also species specific. Females would be resting, kind of, on the ground and then males would be flashing and flying around and if they're interested, then females flash back. So then they start kind of moving towards each other. And that's when the dance begins. And that's when they mate. And hopefully the female is able to lay her eggs, and hopefully those eggs are able to hatch for the next generation of fireflies.

DIRECTOR: How do fireflies species learn their different light languages?

WARE: When it comes to sexual selection, insects, just like people, they have a whole genome and the genome is made up of a bunch of different genes. And some of those genes actually encode behavior. And so this behavior that we're talking about, this kind of light flashing is encoded in the DNA of the fireflies. And so, if there are females and males that have a very kind of orchestrated dance and they're able to find each other, they're able to pass the genes that encoded that behavior that allowed them to find each other, that gets passed on to the next generation. So, before mating has even taken place, there's this kind of checkpoint. Are you the same species as me? Let's look at our flashes. If they're the same love language, then mating takes place. And we think that over time, that's how sexual selection may have shaped this kind of light flashing behavior that we see in fireflies.

DIRECTOR: So, this is a language that's millions of years old?

WARE: Fireflies are really old and they evolved long before we had electric lights, long before humans. And so their whole communication system kind of requires them to be in darkness. Humans have introduced all kinds of things that interfere with that—that's street lights, headlights, billboard lights, stadium lights...

WARE: So what do you think about bright lights like that, Juliana? For light pollution, for fireflies.

CHAUCA: I think those lights, especially bright ones like that, can really inhibit their mating behaviors and the way they're able to communicate with each other. I mean, their flashes, their little patterns. They can't really distinguish them and tell them apart from the light.

WARE: So kind of like if we were in a nightclub and we were trying to talk to someone, you can't hear what they're saying. It's that kind of vibe.

CHAUCA: Yep.

WARE: Tell me all about this community science project that you started.

CHAUCA: So my study is called the Hudson Valley Firefly Project. Basically, I'm recruiting participants to go out in their backyards and observe fireflies and to see how certain factors that are human caused, such as urbanization and artificial light, are affecting them in this region. I basically have participants ranging from six to even 80 and they just go out and count the number of flashes they see in one minute periods.

SARAH JENNINGS (Hudson Valley Firefly Project Volunteer): Usually on a good night, like once the firefly population is like very abundant in my backyard, I can see hundreds of them. Tonight is a little sparse because it’s the beginning of the season.

CHAUCA: And then I also ask questions about whether they're- there's mowing, artificial light, and any other alterations to the property. And from that, I do data analysis and see how the abundance is affected by artificial light and urbanization.

WARE: So those are the two factors that you think are the main drivers of firefly decline?

CHAUCA: I am looking at other factors, so like pesticides—so fungicides, herbicides- herbicides, and insecticides.

WARE: We find that for other insects, too, those are some of the drivers that we think might be, you know, negatively impacting insects. We don't have a lot of great data about how many fireflies there were before the Industrial Revolution. But most of the data that we have for insects kind of from the 1970s, '80s, '90s, and onwards, seems to suggest that most populations have been decreasing. Studies like Juliana's are just starting to establish a baseline so we can understand big trends about where and how insect populations are being affected by human activity.

WARE: So, for the people that you recruited to do the study, are any of them also entomologists or are they people who just are kind of passionate about nature and biodiversity?

CHAUCA: So, these are pretty normal people. I mean, I recruited-

WARE: We all are, even entomologists.

CHAUCA: So I recruited people from local nature preserves and organizations. I have kids from my high school and then I also contacted college departments, biology departments. So, I kind of just spread the word to the general public.

WARE: I can remember when I first started, you know, doing things in entomology, I had a woman named Karen Needham who was at my university, and she was an entomologist. And I thought, okay, there are women who are entomologist, maybe I could be an entomologist. But I still get like a lot of pushback from some people that kind of made it seem like it was, you know, icky or gross or something that, you know, women, you know, people who identify as women didn't do. And hopefully that's changed in- when you were coming up.

CHAUCA: So entomology, I really- kind of came up out of nowhere for me. I didn't really expect to be studying it. That's one of the things that I've realized—take advantage of what's around you. I mean, there's an immense amount of life and just activity that's going on in your backyard. You can be really fascinated by what you're seeing.

[CREDITS ROLL]

WARE: When it comes to fireflies, one of the easiest things you could do that would have a dramatic impact would be to reduce light at night. If you live in the eastern or southern United States, this could mean something really simple, like change the lighting sources in your backyard, on your fire escape. You can also change your light bulbs from being kind of more bluish-toned light bulbs to more reddish bulbs. And wherever you live, it's important to help protect wetlands and moist habitats fireflies depend on. Do you have a favorite rirefly memory? Tell us about it in the comments.