Let’s Talk Fireflies- The When, How, and Why They Glow
Written by A. Srivastava
2,000. That’s about how many firefly species are found worldwide with roughly 150-170 on the North American continent alone. It seems that many have memories of catching and observing these critters throughout their lives, others may be seeing them for the first time. Nearly everyone can identify the glowing lights that seem unique to these beetles, however, you may find these lights all over the world in many different species.
Fireflies are bioluminescent species that can produce and emit their own light. Much like the anglerfish that light up their own ‘bulb’ to attract food deep in the ocean or the bioluminescent phytoplankton that make ocean waves glow a neon blue, fireflies have long captured people’s attention for their trademark glow.
“Fireflies produce light to be able to do a few things…they will use light to scare off predators but they’ll also use light to attract mates,” says Margot Popecki, a graduate student at the University of Georgia who researches firefly biology. “Fireflies, adults, have a light organ in their abdomen. This light organ is yellow in color and it’s where the light is produced…the bioluminescence is taking place there.” Producing light on its own provides fireflies with a range of uses whether it’s using the bright colors to warn predators of being toxic to eat, or flashing at twilight to find and reproduce with mates. The male Blue Ghost firefly, located around the Southern Appalachian mountains, has a blue-white hue and flies only a few feet off the ground to attract females, which have no wings and generally stay in larval form.
“Fireflies are using [bioluminescence] to communicate with each other,” Margot says, “What I’m specifically interested in is how fireflies are able to finetune the way they’re talking.”
If you’ve ever paid close attention to fireflies, you might have noticed yellow and orange glow at twilight and more green glows at night. “If you are watching fireflies at twilight and they have a green light…it’s going to be a lot harder to see them because their green light is now being compared to or blended in with green trees, green grass, green bushes,” Margot explains.
Fireflies may glow a certain color due to evolution. A green glow would be harder for potential mates to make out against the green fields and forests when there is still light in the sky. However, an orange, blue, or yellow is much easier to see and will give males that light up at sunset an advantage over others with different colors. Over time, these colors increase the fitness, or the reproductive success, of the males and become the norm as more yellow glowing offspring are produced. The same can be said for bright green fireflies at night.
“What we’re specifically looking at is the mechanism for that, how does the firefly light color change, why do we see this range of light color from yellow to green…People in the past have thought that this was just from luciferase, (the chemical responsible for the glow reaction) Margot goes on to explain, “but we have noticed, you pick one [firefly] up, it’s [abdomen] is actually orange, just when they’re flashing. And then if you let the firefly go and recapture it in the morning…you’ll see that the light organ is pale yellow.”
This observation has a huge implication, that fireflies possibly have different pigments in their bodies that allow them to change their light color! This could aid them in talking to their mates and foster better communication between them. You can observe them at home by capturing them during twilight, placing them in a jar overnight, and watching the light organ change in color while they signal. The species that flash exclusively at night though, do not show this change in abdomen color through time.
“We’re trying to compare these different firefly species and trying to figure out, do they have the same pigment, do they have any pigment at all, what’s going on in their light organs when they’re flashing?” she says.
Research about the mechanisms behind a firefly’s glow is groundbreaking for our understanding of these creatures in terms of how they glow, interact, and communicate.
It can also be challenging. To maintain this research, Margot has to continuously extract and splice RNA from different fireflies at different times of the day. “That’s why I was interested in RNA to look what genes are being turned up or turned down in those different stages and how they could be related to pigmentation,” Margot explains, who thinks the changing colors can be traced back to genetics, “I was extracting RNA from the light organs and a few different tissues including the eyes.” Such procedures can be very complicated and time-consuming, however to Margot this is all worth it to truly understand fireflies and how they glow. “Fireflies have been captivating people for so long, probably since they first evolved…as they’re just so magical,” Margot tells us.
There are many ways to get involved with firefly research and learn more about their biology as humans have been collecting knowledge since we were first drawn to them.
Margot says that there are many options out there. In addition to checking out books at your local library, there’s, “going to firefly workshops or talks if there are any at your local nature center, that could be a very good way to learn about them. There are a lot of websites that have been created that have information about firefly biology and their life cycle.” Knowing about fireflies’ life cycle is crucial for conservation efforts from protecting the larvae’s habitat to being careful not to trample females on the ground to turning off outdoor lights at night to keep from interfering when they flash around. Knowing is half the battle in protecting these mystical creatures.
1 - Monitoring fireflies around their environment is immensely beneficial for current and future researchers. The Atlanta Firefly Project is a great way to get involved. Check out our Collect Data page or the previous blog post here for more information.
2 - The Xerces Society has many online resources as well as options to help out with fireflies as well as any invertebrate conservation which you can find here: https://www.xerces.org/
3- The Massachusetts Audubon Society, also known as Mass Audubon, also conducts community science monitoring programs much like the Atlanta Firefly Project: https://www.massaudubon.org/get-involved/community-science/firefly-watch
Community scientists are very valuable and as Margot puts it, “It’s really incredible to watch fireflies when you know something about them…it’ll make your experience watching them potentially even more intriguing.”
