Light from the firefly Luciola praeusta at very low temperatures

Abstract

Light emissions from a few Indian species of fireflies at different temperatures have been investigated in recent times. Changes observed in the steady-state and flash emissions in those investigations indicate interesting aspects of their light-emitting systems in the live condition. Here we report emission spectra and pulses from both male and female specimens of the species Luciola praeusta at temperatures much lower than the ones at which they normally emit. When the temperature is decreased to the region of 11.5–11 °C for males or 16.5–15 °C for females, the wavelength peak demonstrates a shift towards blue and the pulses show abnormal increase in the duration. These changes, which are reversible, indicate a slight change in the structure of the enzyme luciferase catalysing the bioluminescent reaction that produces the light of the firefly. This happening is proposed as the reason for the females generally disappearing a bit earlier than the males at the onset of the winter.