COLOUR VISION AND PHYSIOLOGY OF SUPERPOSITION EYE OF A BUTTERFLY (HESPERIIDAE)

An electrophysiological study of the silver-spotted skipper, Epargyreus clarus Cramer, revealed a two-receptor system with maxima at about 440 and 540 mμ. Differential adaptation is possible. The electroretinogram is complex in waveform and demonstrated a maximum flicker fusion frequency of ca. 200/sec. The waveform can be shown to consist of two distinct components; one of negative polarity and of receptor origin, and the other of positive polarity and originating near the basement membrane. The two components demonstrate different action spectra. An analysis of single fibre activity in the optic lobe and protocerebrum reveals a variety of fibre categories responding to various stimulus parameters, including one type whose discharge pattern indicated the wavelength of the stimulating light. Wavelength discrimination was demonstrated in behavioural experiments. The choice of variously coloured model flowers demonstrated a close correlation with electrophysiological observations. © 1969.