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Journalism of Courage
On humid summer nights in Tamil Nadu’s Anamalai Tiger Reserve (ATR), the forest canopy begins to pulse. First one flicker, then hundreds, then thousands — until entire trees appear to breathe with light. To stand in that darkness is to watch the forest write its own rhythm: a synchronous dance of fireflies, signalling across the night sky in bursts of yellow and green.
For decades, villagers and visitors have been surprised at these congregations. But only recently have scientists begun to systematically catalogue the species that compose this living constellation, and to understand what their presence means for a forest under pressure from human activity. A study by the Tamil Nadu Forest Department, with a year-long survey documented in a state-sanctioned report, reveals both the diversity of fireflies in the reserve and the fragility of the conditions that allow them to thrive.
The Advanced Institute for Wildlife Conservation (AIWC), based in Vandalur, carried out a meticulous survey between April 2024 and March 2025. Researchers K Ragavendran and and his team scoured 10 locations — from the forest hamlets of Kozhikamuthi and Varagalayar to the agro-ecosystems of Saralapathi — collecting larvae and adult flies under the guidance of scientists M Gabriel Paulraj, S Siva Ranjani, and S Selvakumar.
In the end, eight distinct species were identified: Abscondita perplexa, Abscondita terminalis, Asymmetricata humeralis, three species of Curtos, Lamprigera sp., and Pyrocoelia sp. DNA barcoding confirmed the taxonomy, and accession numbers were deposited in global databases. Each site yielded its own ecological fingerprint. Saralapathi, with its calm nights and cultivated fields, produced the highest count, dominated by A. terminalis. Manthirimattam and Varagalayar were strongholds of A. perplexa, their males and females carefully tallied along transect lines.
The study also measured environmental variables — temperature, humidity, light intensity, wind speed — capturing the atmospheric stage on which these beetles play out their nocturnal drama.
When asked about the study methods used in a dangerous forest region, especially in the dark, A Udhayan, Principal Chief Conservator of Forests and Director of AIWC, told The Indian Express that their team spent evenings and nights across different parts of the reserve, looking not only at the flashing displays but also at the forest floor, where larvae develop before emerging as adults.
“Fireflies are not active throughout the year — during and after the rains they perform, while the rest of the time they remain in the soil, growing until they become full-fledged insects. We carried out extensive DNA studies and larval collections to understand these life stages,” he said.
The Anamalai Tiger Reserve is best known for its elephants, tigers, and lion-tailed macaques. But the fireflies offer another register of ecological wealth — smaller, quieter, but no less urgent. For researchers, there was an element of risk too. Udhayan said the fieldwork that lasted for about one year, mostly in the dark, always carried an element of risk. “But with the support of experienced forest watchers who know the terrain well, we managed safely and without incident,” he said.
The study was originally inspired by earlier photographic work by Coimbatore-based Sriram Murali, whose study, in fact, triggered further research by the state government.
Fireflies do not glow for aesthetic pleasure. Their light is a coded language of courtship. If the world literature about fireflies are mostly about metaphors, their light is both pragmatic — a sexual signal, and transcendent — a reminder of impermanence. Philosophers have long used fireflies as symbols — of fleeting beauty, of memory, of the limits of human dominion over nature — or credited them for teaching us to think with time.
Scientist Paulraj, who guided the study, said both male and female fireflies possess light organs, “but in males, the organ is stronger as it extends across two segments.”
When a male signals, among the hundreds and thousands of fireflies, the female responds with her own light. In this exchange, the frequency and intensity of the flashes vary, allowing the female to recognise exactly which male is courting her — this is what scientists call a mating signal.
Synchrony, the phenomenon where thousands flash in unison, is not mere spectacle. It is an ecological marker, an indicator of habitat health. Yet this fragile communication system is increasingly interrupted. Artificial light in buffer zones — headlamps, floodlights from religious festivities, even the glow of mobile phones — confuses their signals.
“Artificial light disrupts this delicate process. When background illumination is high, males are forced to expend unprecedented energy to outshine the disturbance, altering their natural behaviour. In our study, areas with abundant fireflies were those free from artificial light. To test their preferences, we developed a phototactic movement device in the shape of a cross — one arm left in darkness and the others lit in different colours. Consistently, the fireflies chose the darkened arm, demonstrating their strong preference for darkness,” he said.
The scientific findings also capture local knowledge. In a questionnaire survey across Malasar and Irula settlements inside the reserve, 97 per cent of respondents reported awareness of fireflies and a sense of their decline. Older residents often blame pesticides in surrounding farms and the contamination of streams that once ran clear. For them, the shrinking of these summer light shows is not an abstract loss of biodiversity — it is a tangible diminishment of seasonal life.
The study also gives a prescription: protect darkness. The AIWC report urges minimising light pollution around forests. Fireflies, scientists note, could serve as “indicator species” for the wider impacts of artificial lighting on nocturnal wildlife.
