Coherence of the light of firefly Luciola praeusta

Abstract

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 μm. 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.