Biologist Sara Lewis doesn’t just study fireflies—for her, fireflies are a living reminder that the world is pure magic. In this episode, the author of Silent Sparks: The Wondrous World of Fireflies unpacks the science of fireflies. These members of the beetle family are one of only a handful of terrestrial creatures capable of generating light. How fireflies glow, why they glow, and how their living conditions and populations are changing—Sara explains all of this and describes the relationship between us and them. Sara uses fireflies to make a case for wonder, which she says is something we can and should practice every day. “For me, paying attention to the natural world feeds my sense of wonder, and I actually think that’s one of the most important senses that we have–and that it may be underused.” – Dr. Sara Lewis, Professor Emerita in Biology at Tufts University; Chair of the Firefly Specialist Group in the International Union for the Conservation of Nature.
The International Union for the Conservation of Nature (IUCN) is the global authority on the status of the natural world and the measures needed to safeguard it. The Firefly Specialist Group that Dr. Sara Lewis leads is dedicated to protecting firefly species whose populations are threatened. Its members engage in research, advocacy, and public outreach (like the establishment of an official “World Firefly Day”). To learn more about the work they do, visit IUCN’s firefly webpage. You can also read their most recent report here, which includes detailed information on how specific species of fireflies are doing.
Sara is the co-founder of Fireflyers International Network, a group of firefly researchers and enthusiasts. This is the group that first coined the word “Fireflyer” to mean a “firefly chaser. A person who thinks about lightning bugs.” Learn more about their work here.
In this episode, host Jill Riddell confessed how difficult it was for her to fully comprehend how fireflies are able to light up. She promised listeners that we would include something on this webpage that would hopefully make firefly’s most glorious accomplishment more understandable — for her and for others. So… here goes.
Think of a firefly as having a tiny lantern embedded inside its body — and that lantern takes up about 10 percent of the firefly’s overall size. Even more amazing: the lantern has an on-and-off switch. But that “switch” is not mechanical or electrical — it’s entirely chemical.
You know those glow sticks at parties and concerts? Well, the firefly’s lantern works on the same basic principle: chemistry. There’s no fire involved. The light a glow stick or a firefly makes is cold — it doesn’t give off heat like a candle or a lightbulb.
Both glow sticks and fireflies produce what’s called “chemiluminescence” — that’s a light that gets created as the result of a chemical reaction.
Inside the firefly’s lantern, there’s an enzyme scientists call “luciferase.” This enzyme is a kind of protein shaped like a baseball glove. It holds a smaller molecule called “luciferin,’ which fits right into that glove. Then, using oxygen (and a few helper molecules), luciferase sets off a chemical reaction. As luciferin gets excited and then returns to a calm state, it gives off a tiny flash of light. Cool, right?
Order Sara’s book, Silent Sparks: The Wondrous World of Fireflies from your local bookstore, online here from the book’s publisher (Princeton University Press), or from Amazon. Also, check out the website for the book, which has additional writings and resources, and the beautiful trailer.
To learn more about the firefly habitat restoration efforts in Taipei, read Sara’s blog post on the initiative.
As Sara mentions in the episode, fireflies hold a special place in Japan. During Japan’s period of rapid industrialization, the number of fireflies was radically reduced. Communities began organizing local clean-up efforts and “firefly festivals” (hotaru matsuri), and slowly, populations recovered.
Historically, in Japan, poets used fireflies to symbolize summer and its ephemeral beauty. One of the famous writers of haiku, Kobayashi Issa, utilized them extensively. Here’s an example of one that speaks to the tensions between nature and cities:
Read more about fireflies in haiku in this article.
