Coherence of the Light of Firefly Luciola praeusta

Firefly bioluminescence has given rise to several curiosity-driven as well as application-oriented studies. The emission spectrum of the Indian species of firefly Luciola praeusta Kiesenwetter 1874 (Coleoptera : Lampyridae : Luciolinae) has been shown to consist of two broad green- and red-coloured sectors, with a narrow yellow one in between. Here we present interference patterns of light of this firefly species using a Michelson interferometer for different positions of the two reflecting mirrors, up to a path difference of 11.5 cm. Next we employ Young’s double-slit method with the lantern of the firefly as the source at pinhole separations of 160, 170 and 180 m. From the fringes obtained in these two sets of experiments, we conclude that the light of the firefly exhibits excellent temporal as well as good spatial coherence properties.