Spectral mechanisms of the compound eye in the fireflyPhotinus pyralis (Coleoptera: Lampyridae)

Electroretinograms (ERG) were recorded from dark- and chromatic-adapted compound eyes in the dusk-active firefly,Photinus pyralis ♂, at different wavelengths ranging from 320 to 700 run and over 4.5 log units change in stimulus intensity. ERG waveforms differed in the short (near-UV and violet) and long (yellow) wavelengths (Fig. 1). Waveform differences were quantitated by analysis of rise and fall times as a function of the amplitude of the response. Rise times were found to be relatively constant for all stimulus wavelengths. However, variations in the fall times were detected and followed characteristically different functions for short and long wavelengths (Fig. 2).