When did you last see a firefly? Consider yourself lucky if the encounter is not older than a year because this light-producing extraordinaire has a rare favourable reputation among creepy-crawlies – it is believed to be a lucky charm, a good omen and a wisp to guide one through meandering forest-trails.
However, fireflies themselves seem to be down on their luck; they are fading fast. The last time I saw one in Banasree, I had not even completed school. I have met them a couple more times. But for that, I had to go to some of the remotest corners of the country. I fear many of you have the same nagging question – where did all those living lights go?
Today's tale is a toast to our memories with the beloved Jonaki Poka. Also, consider it as a story for the urban kids, for many of them have not seen the fabulous green flickers under a starry night. And it is said that a thing not seen often is soon forgotten. But something written is hard to erase, so let the fireflies glow forever in stories and in our imaginations.
A large family
Fireflies are diverse. You may even say that they are mega-diverse! There are a staggering 2,000 species of fireflies in the world. However, they do not grow big. Most do not grow beyond a couple of inches.
Fireflies are cosmopolitan – you can see them in the teeming tropics, but you can even get one in dry temperate climate.
Now, what are they? Technically speaking, fireflies are not "true flies." They are not related to the fly you see hovering over your fruit. Here is a quick trick to discern which is which: The flies that have the word "fly" not attached to their names as a single word, such as a fruit fly or a sand fly, are considered "true flies" in science. All other title holders are not flies, including dragonflies and butterflies and yes, fireflies.
Fireflies are beetles of the family Lampyridae. Simply put, fireflies are a very special group belonging to the largest and the most diverse insect order.
More than a simple string light
So, how do they produce light? Generally, the animal world does this by two major means. The easier method is to do it by culturing glowing bacteria within their bodies. The second, and the harder way, is to produce light by enzymatic reaction. The enzyme luciferase works on a special beetle protein called luciferin. To run the reaction, a firefly also requires magnesium and oxygen. All of this happens inside their tiny bodies. Most lights are yellow and green in colour with strong iridescent hues. A red flickering light can be noticed in some.
The intensity of a firefly's light can only be described as otherworldly brightness. The energy they use to produce light is nearly 100 percent efficient. On the other hand, the relict wire-filament bulb can utilise only 10 percent of its energy used to produce the light – the rest is wasted away as heat.
But why do they produce this light? It has long been assumed that fireflies warn us by flashing their light, but that is not the case. According to the Scientific American, only night-time fireflies glow and it is a mode of communication. Generally, males do this to attract a mate. However, in some unique species, female and non-flying juveniles produce lights as well.
A new discovery from Bangladesh
Think about the shape of a firefly. What do they look like? Cannot draw any? Well, at night, the flickers take all our attention. Let me help you.
Adult fireflies do match our common perception of insects. But juvenile non-fliers are different. In fact, they can be so different that I could not believe my eyes when I saw one.
It was in 2019. I was at the Satchari National Park – a northeastern forest of Bangladesh. I was outside the dorm, right after a deep summer shower. Suddenly, I noticed a pair of green iridescent freckles on the dorm patio. And they were moving in snakelike trail, twisting and turning. I turned my torch on. What I saw instantly reminded me of a fossil specimen. The plated body, the trigonal shields, the gradually tapering body and the movement matched with a reincarnation of trilobite – an insect that went extinct millennia ago. Later, I deciphered the identity. It was a larva of Lamprigera giant firefly, the largest of its family. It was peaceful, avoiding my light beams and went hiding into the bushes soon.
I shared the news with my good friend Harish Debbarma, a Tipperah citizen scientist and a parabiologist. He told me about the abundance of the species in the park. But has the insect been noted anywhere else in Bangladesh? There are no anecdotes.
Basically, you are not only reading about a unique species, but an introduction with an insect that is new to Bangladesh.
Complimentary pest control
There is one thing you might not be aware of; firefly larvae are very effective predators. They prey on many invertebrates that can wreak havoc on harvests. From ever-hungry garden snails to notorious caterpillars, all common pests are favourite platters of the fireflies.
Pest control for your backyard just got cheaper and brighter!
The fading will-o'-wisp
Unfortunately, all the good things and charming stories you have read this far are not helping fireflies survive. In fact, they are disappearing, unnoticed and ignored. Compared to the honeybee, for example, the outcry for fireflies is not loud, and often completely silent. The extinction process is relentless.
I can give you one picture from Andhra Pradesh, India – a region not very far from Bangladesh. A 2020 investigation revealed a significant reduction in the density of fireflies in the area. Scientists found only 10-20 individual insects beaming per 10 square-metre. It was more than 500 in 1996.
I asked many people about their experiences with the firefly while writing this piece. The response was nearly identical every time: "I don't know when I last saw one. They are not that common anymore."
Are fireflies losing the race? Are their night-time glints fainting in front of ghastly city lights? Is there no hope for the forest wisps anymore? Are the good omens leaving us one by one?
Can we truly bear a Bangladesh in silent spring?
More on light producing incects
Fireflies are not the only insects that can produce lights, however. Bioluminescence is notably observed in two more beetle groups – the glowworm and the railroad worm. Railroad worm can simultaneously produce green and red lights.
There is a fungus gnat that buzz in caves, a cousin of the mosquito, that forms glowing, sticky web to hunt unsuspecting prey.