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Đom Đóm: Why the Light Is Going Out for Fireflies in Vietnam

Much like their brief existence on Earth, once-common fireflies are quickly disappearing from Vietnam’s natural and oral histories.

When I was a wee schoolchild, rather than a biology textbook or a field trip, fate (and the education ministry) decided that my first lesson about fireflies should come in the form of a reading exercise.

Endearingly titled “Anh Đom Đóm” or “Mr. Firefly,” the excerpt was taken from a poem by famous children’s literature author Võ Quảng, whose allegorical writing assures us that Mr. Firefly is not just a mere creature, but a metaphor for dignifying virtues that the young should learn, like “diligence” and “perseverance.”

“Mr. Firefly” bore no enunciation or comprehension challenge for my class of 42 third-graders, but it presented a fatal flaw in our upbringing — by that point, few of us had seen or even knew of the titular animal. The working assumption was that our parents should have taught us, but they most likely never had a chance to see an actual firefly either. Our brave new world has ushered in an age of advanced, high-efficiency bulbs, and with them, the eclipse of nature’s glowing insects.

A keeper of country life and childhood discourse

Long before the poem and this oblivious generation came about, fireflies roamed freely across Vietnam and starred as a recurring character in the country’s premodern cultural canvas.

Their presence is most notably attached to fictional accounts of feudal-era scholars such as Mạc Đĩnh Chi, Nguyễn Hiền, Bùi Xương Trạch, and Nguyễn Huy Tốn. Although these figures lived hundreds of years apart, a shared narrative constituted their “origin story” — underprivileged children who substituted expensive fuel-based lamps with fireflies trapped in egg shells to study at night. Such resourcefulness earned them a place in the kingdom’s royal court and inspired reverence throughout history.

By the mid-20th century, the electric bulb made its debut in Vietnam, but few could afford the innovation. Industrialization was just beginning and farming was the predominant means of sustenance, with the countryside still filled with endless woods, grassy plains and fields. 

Photo courtesy by Thông Nguyễn.

Memories of this time are preserved by nostalgic elderly people in stories about their epic childhoods — days where fun meant one could spring along unpaved paths chasing swarms of fireflies, catching the unlucky few, and storing them in ink jars or glass containers for a miniature light show.

Did you know?

The eggs, larvae and pupas of some firefly species also possess bioluminescent properties.

But more than just playful distractions for children, fireflies offered a more profound meaning for adults in the past. Amidst war and poverty, people saw flickering fireflies as offering an enchanting sense of comfort and happiness — a stark contrast to heavy farmwork, dark underground tunnels and the terror of a looming enemy. And perhaps most importantly, fireflies were the harbingers of agrarian rebirth. As the first summer showers fell, the insects took flight and signified that the planting season had arrived. A farmer’s proverb reflects this idea: “Bao giờ đom đóm bay ra, hoa gạo rụng xuống thì tra hạt vừng,” meaning that “When the fireflies fly, and the red silk cotton falls, besow the seeds of sesame.”

Lacking modern scientific knowledge, people resorted to supernatural beliefs to explain the insects’ illuminating ability: they must have been the souls of the departed, particularly those that perished due to war and famine, remaining on Earth to light the way for those who stayed. This is perhaps part of the reason why the insects enjoyed a respected reputation with cameos in legends that further elevated their status. But human curiosity gave way to microscopics, which revealed neither noble nor divine cause of the illumination. The truth is a tad less poetic.

An evolutionary purpose

For fireflies, the ability to glow in the dark serves a primary evolutionary purpose equivalent to posting a shirtless selfie on dating apps. Fireflies exhibit sexual dimorphism, wherein the males have wings while females do not. Thus, females will situate themselves somewhere high to watch males compete for their attention. Males that can spark longer show they have more stamina, which suggests good genes, and are thus more likely to attract a mate. Should the female “superlike” the male, she will emit a similar light signal to inform him that she is a match.

Through science, we have also come to fully understand the mechanism of this process: fireflies emit light through the final segment of their abdomen. Inside their stomach lining are rows of luminescent cells governed by neurons and tubes known as tracheoles. And in the innermost layer, a reflective cell layer functions as a mirror to redirect the light outward.

Did you know?

One would need approximately 833,000 fireflies to attain the average brightness of an LED bulb (about 500 lumens).

Breaking it down further, luminescent cells contain two types of substances, luciferin and the oxidative enzyme luciferase. In the right conditions, they form a series of chemical reactions that produce light. Fireflies control this entire chemical reaction by adding or subtracting oxygen from their abdominal chamber, which, when performed synchronously by a swarm, creates the fairy-tale-like glimmering scene that generations of people adored.

Having deciphered the cause for the ability fireflies have had for millions of years, humans sought to put it to our use. Out of its many applications, luciferase extracted from fireflies is most prominent in the medicinal field, where it’s used to monitor hydrogen peroxide levels in experimental organisms, and in the food industry for the detection of contaminated food cells.

Why the light is going out for fireflies

A sad (and common to the point of repetitive) paradox is that by the time we've begun to understand an animal’s true nature and harness it, we are driving it to extinction. Poor little fireflies are no exception. Research and statistical reports show that the world firefly population is on the decline and heading toward extinction due to, surprise surprise, humans. Light pollution from urban expansion is disrupting the insect’s circadian rhythms and mating rituals, while pesticides are killing larvae nested underground. And doubling down on the destruction, fireflies' natural habitats, such as mangroves, are shrinking due to land development.

Evidence of this biological damage is clear in Vietnam, where the process is accelerating. In the 19th century, scientists discovered nearly 30 species of fireflies indigenous to Vietnam, but by the time the most recent statistics were published in 2021, the confirmed count fell to fewer than six. And even without statistics, one can detect the gradual loss of fireflies through anecdotal observation. When was the last time you saw a firefly where you live? Most likely, you haven't. That is because the species that once roamed freely countrywide now only exists in holdouts like national parks such as Cúc Phương and Cát Tiên, and remote areas.

I contacted Dr. Phan Quốc Toàn, a leading Vietnamese entomologist from Duy Tân University, in the hope of finding a spark at the end of the tunnel. But the expert’s blunt answer only confirmed the creature’s eventual dimming, and there is not a single person in Vietnam that can stop it from happening:

Photo courtesy by Thông Nguyễn.

“In Vietnam, there is barely research on fireflies, let alone conservation programs for this species.”

And so, just a few zodiac cycles late, a class of third-graders and so many more like me missed the golden age of fireflies and forewent a childhood that would have been more magical with them. It seems that fireflies and electric bulbs have swapped roles for good, for they have become a precious commodity.

If you ever find yourself one of the privileged few that get to witness fireflies again, catch your breath, but refrain from catching them, since there’s a chance it might be one of the last specimens you are encountering. Instead, entertain the alternative, where you just admire the creatures from afar and sympathize with how similar both their and your existence are: here for a moment, and then gone in a flash in a dark, empty universe. Much like the wise words of author Nguyễn Xuân Khánh, who once wrote: "Men are not so different from fireflies. No one lights them, but somehow the fireflies are still lit. It means that men have an innate light in them. In the dark night, the fireflies try their best to glow on their own. The light is very small, very weak. But it is light regardless."

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