Synchronous and Rhythmic Light Display by a Panoramic Congregation of Fireflies at Varagaliar, Anamalai Tiger Reserve

Synchronous flashing of a large congregation of fireflies observed at Varagaliar, located in the Anamalai Tiger Reserve in the Tamil Nadu part of Western Ghats (10°25.09' N, 76°51.94' E, Elevation 2100 ft) is reported here. Typically, the fireflies on the topmost part of the tree crown flash a yellowish green light, almost immediately followed by similar light flashes serially by the fireflies below. The flashing pattern in each tree repeated itself cyclically, and other neighbouring trees had similar but unique synchronous displays. After a few cycles, fireflies in all the trees flash three times in unison as if appreciating their spectacular performance. The whole forest landscape resonated with pulsating waves of multiple kaleidoscopic flashes of light from several clusters of fireflies until dawn. This annual spectacle is observed only during the month of April, before the onset of the south-west monsoon, perhaps coinciding with the mating season of the adult insect that lives for about a month. Synchronous fireflies have also been reported elsewhere from Southeast Asia, the Great Smoky Mountains National Park, Elkmont, USA, and Brazil. Conserving this unique phenomenon at Varagaliar for posterity, necessitates a better understanding of the species composition of the fireflies involved in this phenomenon, the reasons for their synchronous behaviour, the geographical area that is congregated by these insects, the unique plant species composition, and the ecology and ecoclimate of this habitat that makes it an exclusive niche for congregation of synchronous fireflies.

Keywords: Anamalai, annual spectacle, conservation, cyclic, ecotourism, glow worms, mating, monsoon, synchronous fireflies, vegetation, Western Ghats.