A diurnal moth superposition eye with high resolution Phalaenoides tristifica (Agaristidae)

Abstract

This common Australian moth flies slowly and only in bright sunlight, but the compound eye has a sharply focused superposition image, to which 120-150 facets contribute. A distant point source is focused to form a blur circle on the retina. The diameter of this blur circle at 50 % intensity, calculated from the width of the angular distribution of eyeshine, is 1.5- 2.0° subtended at the centre of the eye, matching the interommatidial angle. The compromise between acuity and sensitivity, which is dependent on rhabdom spacing in relation to the blur circle diameter, has been struck with approximately 50% of the converging light from a distant point source falling on a single rhabdom. The F value of the focusing arrangement, defined as (focal length/aperture) is approximately 0.9. Show more