Decoding the Language of Fireflies

[Curator Jessica Ware chases after blinking fireflies in a lush garden at dusk.]

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. 

[A firefly crawls over her hand and takes off into the night.]

WARE: 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? 

[Close up of a firefly resting on a stick and blinking. Ware reaches out and tries to catch a firefly in flight.]

WARE: It's why that's so fascinating. 

[Time lapse of a field at night. Firefly flashes leave stuttered trails and bright green smears across the landscape.]

WARE: Different species of fireflies—they each speak their own language. Kind of like a language of love.

[Juliana Chauca, a teenager, holds a firefly and brings it close to the camera, opening her hands to display it before it flies off. She smiles with delight.]

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.

[Ware and Chauca walk together on a community garden path. Tall apartment buildings rise behind them.]

[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.

[Yellow blinks of light pop in and out over a flowering lawn in a city park.]

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. 

[Fireflies blink in an empty city lot. One crawls on a chain link fence and then takes off, flashing. Another flies and blinks over flowers in a garden at early evening.]

WARE: That biochemical reaction releases energy in the form of light and pow, we've got flashes. 

[A firefly blinks, perched above another on a low plant. The second blinks in return.]

WARE: 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 holds out an insect net. Inside is a single firefly.]

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

[Ware walks through community garden paths, carrying her insect net.]

[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. 

[Ware stands outside the entrance to the Museum. In a sped-up sequence, she walks inside and through the halls to the door of the invertebrate zoology collections.]

WARE: I am a curator and what I do is I study insect evolution. Come on in.

[The camera follows Ware into the collection space—a large room filled with rows of compactor shelves.]

DIRECTOR (off-camera): 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 library for insects. 

[Ware whirls a rotating lever to open a row of cabinets.]

WARE: Do you want to look at some fireflies up close?

DIRECTOR (off-camera): 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. 

[Various beetle species—a long black beetle, with long black antennae; a beetle with striking red legs opens its wings and flies off; a ladybug chows down on aphids.]

WARE: Fireflies are a kind of beetle. And beetles, unlike flies or like true bugs, have hard wing covers and chewing mouthparts.

DIRECTOR (off-camera): Are there are a lot of beetles out there?

[Drawers of pinned beetle specimens display incredible varieties of shape, pattern, and color.]

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.

[Ware holds a drawer of beetle specimens.]

DIRECTOR (off-camera): 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 points to a row in the collection shelving units and spins the handle which widens that aisle. She walks down the row and opens up a cabinet.]

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

DIRECTOR (off-camera): 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 est discipulus malus. I was a bad student. So, here they are. 

[Ware pulls out a drawer of firefly specimens. Close-up shots of various firefly species.]

WARE: So there's lots of different species of fireflies. 

[An extreme close-up of a single pinned ant specimen.]

WARE: And I think, like often when we say ants, we think that there's just one kind of ant, right? 

[An extreme close-up of a single pinned mosquito specimen. The camera pulls out to reveal a drawer full of hundreds of specimens, representing a number of species.]

WARE: And when we say mosquito, we think that there's just one kind of mosquito. But actually, there's thousands of species. 

[A single firefly hangs on a window, displaying its underside and flashing lantern.]

WARE: And it's- the same is true for fireflies. 

[A circle is drawn around the firefly and text appears, reading, “2,000 firefly species.” That circle is then surrounded by a significantly larger one, and the text, “6,500 mammal species.”]

WARE: So there's over 2000 species of fireflies globally, and there's only like 6500 species of mammals.

[Close-ups of various firefly species in the research collection. Despite being different species, they look relatively similar—long, dark, winged bodies.] 

WARE: So there's a lot of firefly species out there, relatively speaking.

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

[Ware pulls another drawer out of a cabinet, displaying more boxes of fireflies.]

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.

[Ware stands in the community garden in the late afternoon.]

DIRECTOR (off-camera): Do all fireflies flash?

WARE: So, not all fireflies flash. A lot of them do. 

[Firefly larvae display their bioluminescent glow.]

WARE: 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. 

[Ware walks and talks in the community garden.]

WARE: 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 taste pretty gross to predators. So perhaps being glowing, you know, would have signaled I'm distasteful, don't eat me.

DIRECTOR (off-camera): 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. 

[SEXY SMOOTH BEAT DROPS]

[Close-ups of fireflies blinking to one another, different species flashing different colors.]

WARE: 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. 

[A time-lapse of firefly flashes at night pauses and labels indicate patterns produced by different species: “Photuris versicolor” with a long, bright green smear, and “Photinus carolinus” with a stuttered line of yellow-ish dots.]

WARE: And then the patterns of the flashes are also species specific.

[A female firefly sitting on a leaf turns her rear end up and flashes. A nearby male circles closer and then lands behind her. They start mating.]

WARE: 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. 

[Two fireflies turn end-to-end, mating.]

WARE: And that's when the dance begins. And that's when they mate.

[Ware speaks to the camera in the community garden.]

WARE: 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 (off-camera): 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.

[Fireflies blink over a wide lawn in early evening.] 

WARE: And so this behavior that we're talking about, this kind of light flashing is encoded in the DNA of the fireflies. 

[Ware speaks to the camera in the community garden.]

WARE: And so, if there are females and males that have a very kind of orchestrated dance and they're able to find each other…

[Close-up of a male firefly blinking near a female and crawling on her to mate.]

WARE: …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. 

[Ware speaks to the camera in the garden, holding her insect net.]

WARE: 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.

[A firefly takes off from a leaf, leaping into the air, opening its wings, and blinking as it flies.]  

WARE: 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.

[Ware stands in the community garden at night. The New York City skyline and its lights rise behind her.]

DIRECTOR (off-camera): 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. 

[Car headlights drive swish past a field where fireflies flash. Bright stadium lights illuminate a soccer field at night.]

WARE: Humans have introduced all kinds of things that interfere with that—that's street lights, headlights, billboard lights, stadium lights...

[Ware and Chauca stand in the community garden at night, looking at all the nighttime park lights around them.]

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

[TEXT ON SCREEN: Juliana Chauca | Hudson Valley (NY) Firefly Project Researcher]

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 and Chauca walk in the paths of the community garden.]

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. 

[Chauca and one of her volunteer counters, Sarah Jennings, stand on the back deck of a suburban house. Jennings records firefly flashes in the yard with her cellphone.]

CHAUCA: 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.

[TEXT ON SCREEN: Sarah Jennings | Hudson Valley Firefly Project Volunteer]

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.

[Jennings and Chauca chase fireflies in the backyard.]

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 and Chauca walk the paths of the community garden.]

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. 

[Close-up of a firefly on a branch.]

WARE: We don't have a lot of great data about how many fireflies there were before the Industrial Revolution. 

[Ware speaks to the camera in the community garden at night. Several fireflies blink in the pathways.]

WARE: 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. 

[Jennings logs firefly observation data on her cell phone.]

WARE: 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 and Chauca talk in the community garden.]

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 entomologists, 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. 

[Chauca holds a firefly in her hand and then releases it, flashing, into the night.]

CHAUCA: 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.

[A single firefly crawls on Ware’s hands and then takes off.]

[Credits roll.]

[Ware speaks to the camera in the community garden. Close up of a firefly hanging under a leaf during the day.]

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. 

[A light mounted on the outside of a building turns off. FIreflies flash in a field at night.]

WARE: 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. 

[A warm, orange-y bulb glows inside an outdoor porch light.]

WARE: You can also change your light bulbs from being kind of more bluish-toned light bulbs to more reddish bulbs. 

[Expansive landscape of a waterway surrounded by mountains.]

WARE: And wherever you live, it's important to help protect wetlands and moist habitats fireflies depend on. 

[Close-up of a firefly on a branch.]

WARE: Do you have a favorite firefly memory? Tell us about it in the comments.