Of Fireflies and Glowworms

When we were young, we used to see fireflies in the garden a few weeks in a year. What a magical experience it was! Like the stars had come down to visit us.

After that, I did not see them for many decades. Either I did not live in the right place, or I was not lucky enough to spot them in the short window that they glowed. But in the last few years, since we moved to Bangalore, I have been sighting a few. Year after year, the same two spots in our community hosted them—shrubby areas on the periphery. This year, for some reason, I am seeing many more . Each spot has only a couple, but from two, the number of spots has risen to six or so. That definitely sounds like good news!

But what are fireflies? Sorry if this takes the magic and romance away, but they are a type of beetle!  There are over 2,000 species of firefly spread across the world on every continent except Antarctica. However, in India, we have only eight. They are generally seen in the pre-monsoon season.

Why do fireflies twinkle? As is usually the reason for most beauty in the natural world, it is to attract a mate and reproduce! Fireflies use flashes as mating signals and the flashes we see are generally from males looking for females. They flash a specific pattern while they fly. If a female waiting in the greenery nearby is in the mood, she responds back with a flash. They will continue this flashy exchange till the male locates the female and they mate. Each species has its own pattern so that males and females of the same species can identify each other.

And how do they twinkle? Through a phenomenon called bioluminescence. At the risk of taking away even more romance, it is when two chemicals found in their bodies, luciferin and luciferase, lead to a reaction in the presence of oxygen, adenosine triphosphate  and other compounds, that they twinkle. The light they produce is called ‘cold light’– that is no heat is produced during the reaction. Which is a good thing, as otherwise not only would it waste energy, but also burn the poor creature.

This year was a lucky year, as I am seeing so many fireflies. Firefly populations are rapidly decreasing because of habitat degradation, light pollution, pesticide use, poor water quality, climate change, invasive species, and over-collection. In India, pesticide use may be the most significant cause of the falling numbers.

I was lucky enough to see another ‘glowing phenomenon’ — the glow worms of New Zealand. Of all my nature-travel experiences, I would count this as THE top! In an experience like no other, boats take groups of tourists through a waterway in an intricate web of caves. It gets darker and darker, till you are in the darkest-dark you will ever experience. The boat-captain guides the boat by pulling along ropes tied on the sides of the cave. Just as you start to wonder whether the sight you will see is worth the risk of being toppled into a water course of unknown depth in pitch dark which will make rescue impossible, you are rewarded with flashes of light which grow in intensity as you proceed. And then you know it is worth it as you see constellations of twinkling glow worms on the roof and sides of the cave!

These are glow worms—again, not actually worms, but in the case of those found in Australia and New Zealand, the larvae of fungus gnats, an insect that looks like a mosquito. Their bioluminescence works much the same way as that of fireflies, and they emit light from an organ near their tails that is similar to a human kidney. However, in their case, the glow is mainly used to attract prey. Smaller insects and flies are drawn to the light and fly towards it.

These special sparklers and their habitats are fragile. We don’t know what human actions can push them over the brink. We need to take care that our carelessness does not take the glow from our lives.

-Meena

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