Magic lamps of the wild: The enchanting world of fireflies

When I was yearning for a little piece of earth to belong to, I sought out the cloud forests of the Western Ghats, the land of my ancestors. But the Shangri-La of my dreams remained elusive for long, and we settled for an arid patch instead, in the plains of Mysuru district.

As one season turned into another, realisation dawned ever so slowly that Navilu Kaadu, our wild savanna, didn’t just nurture 10 tamarind trees, but several wildlings, no less captivating than the ones in tropical forests. One of them even brings the mystic of the rainforest to Navilu Kaadu. Tiny airborne sequins embellish the veil of twilight draped gently on our open grassland — fireflies. A few of them drift beyond our porch at twilight like flecks of glowing ember, on the cusp of the monsoon season.

Fireflies are soft-bodied, mostly nocturnal, bioluminescent beetles under the family Lampyridae, within Coleoptera, an order comprised of winged beetles. Bioluminescent beings emit light to draw mates, warn off predators, or hunt.

Fireflies have fired human imagination for as long as our race has walked the planet. Scientists propound that the larvae of fireflies originally emitted light and continue to do so to avoid being eaten, alerting predators to the toxins in them, a defense strategy called aposematism.

Somewhere along their evolutionary trajectory, adult fireflies figured that lighting up their backsides could potentially be a rewarding dating hack and started to beam light from their bums to draw mates. Further along, diabolical adult female fireflies of Photuris, a genus not endowed with toxins, hit upon a sinister plan. The enchantresses began mimicking the flashing pattern of the females of the fireflies belonging to the genus Photinus to draw mates. Photuris females love-bait Photinus males with the borrowed flash pattern, and prey on them, to make their victim’s toxins their own, in turn making themselves unpalatable to predators.

How do fireflies conjure light? These beetles have specialised light-producing organs called photophores in their abdomens, where luciferin, a light-emitting compound, reacts with an enzyme called luciferase. Oxygen drawn through the beetle’s abdominal breathing tube, magnesium ions and Adenosine triphosphate (ATP) fuel the reaction to produce cold light — a type of light with no heat.

All species of firefly larvae glow, but only a few of them light up as adults. Some firefly species that are diurnal or active during the day rely on good old pheromones or chemical signals to draw mates.

The mating rituals of fireflies and their dazzling display of synchronous flashing are the stuff of legend. The males take wing and illuminate their derrieres to bewitch female fireflies gazing up at them from the ground. If a female is taken in by a male’s flashing moxie, she reciprocates with a flash of her own. The gent then floats down to meet the lady and the pair mate.

Fireflies need moist habitats to complete their lifecycles, and the larvae need plentiful prey; hence their reliance on monsoons, and their abundance in the tropical rainforests of the Western Ghats. Mated females lay eggs just beneath damp soil or on emergent vegetation. The eggs hatch in about four weeks. Much of a firefly’s lifespan is spent in the larval stage. Come rain, the larvae emerge and then pupate for around two weeks. Adult fireflies live for barely a couple of weeks.

Fireflies thrive in undisturbed terrestrial and riverine landscapes, and their presence indicates a balanced ecosystem. Disturbances to the topsoil and unchecked pesticide and herbicide use sully firefly habitats. Artificial light disrupts firefly photic signalling patterns that are crucial for defence against predators and to attract mates. Without concerted efforts to secure firefly habitats and curb light pollution, these magic lamps of the wild may cease to illuminate our natural landscapes altogether.

Rooting For Nature is a monthly column on an off-kilter urban family’s trysts with nature on a natural farm. The author runs Green Goobé, a sustainable venture committed to a greener, cleaner planet. Reach her at [e-mail] or @ramyacoushik on Instagram.