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Abstract:
The sensitivity distribution of visual elements in the front region of the compound eye of Musca is investigated by means of intracellular micropipette recording. This distribution approximates a Gauss-function of 7.7 degree half-value in the horizontal plane. Using a “bleaching effect” of the Musca compound eye as an indicator, the angular distances between the optical axes of adjacent ommatidia are measured and found to vary between 2.3 and 3.9 degrees. Thus the visual fields of adjacent ommatidia strongly overlap. Based on these findings a calculation reveals that less than 12% of the mean efficient light flux is received from the anatomically determined visual field of the ommatidium. Similar percentages for Calliphora (less than 20%) and Limulus (less than 19%) result from evaluation of data collected by other investigators. — Light entering the visual element from different directions (more than 5° apart) is demonstrated to be 1.2 to 1.4 times more effective than light received from the same direction. — Consequences of the overlap of visual fields of adjacent ommatidia for perception of motions and patterns by the compound eye are discussed.
