DIURNAL CHANGES IN THE ELECTRICAL RESPONSE OF THE COMPOUND EYE

Abstract

The electrical responses from the compound eyes of certain beetles follow a definite diurnal cycle. When these beetles are kept in total darkness and under approx. constant environmental conditions the electrical response to a brief exposure of bright light obtained during the morning and afternoon hrs. (day-type) is markedly different from the response obtained during the later afternoon and evening hrs. (night-type). The day-type of response is relatively simple and similar in many respects to the electrograms which have been recorded from the eyes of certain grasshoppers and butterflies. The night-type of response, always much larger, contains complex elements such as are seen in connection with the eyes of the Cecropia moth and other moths. This diurnal periodicity of the electrical potentials, which has been found to occur in Chlaenius diffinis, Chlaenius iomentosus, Hydrus triangularis, Harpalus caligi-nosus, and Harpalus pennsylvanicus, persists as long as the animal remains alive. Light-adaptation of the eye reduces the magnitude of both the day-type and night-type of responses, but the wave form is altered only in the case of the night-type of electrogram. The possibility is discussed that this rhythm in electrical potentials is related to a diurnal migration of some of the eye pigments. Such diurnal variations in the movements of eye pigments have been observed in the case of a number of invertebrates.