A micro-anatomical investigation of dark and light-adapted eyes of <i>Chilades pandava</i> (Lepidoptera: Lycaenidae)

Abstract Chilades pandava (Horsfield) (Lepidoptera: Lycaenidae) is a notorious defoliating pest of Cycas spp. (Cycadaceae) in the tropical and subtropical regions of the world. The primary visual receptors of butterflies are the compound eyes. To understand the perception of visual stimuli in Ch . pandava , the external morphology and internal microstructure of Ch. pandava compound eyes were examined using light and scanning electron microscopy. The number of ommatidia was approximately equal in both sexes, and the eyes of Ch. pandava are of the apposition type, with the crystalline cone directly connected to the rhabdom. Significant differences were observed in the length of the crystalline cone and the width of retinula cell nucleus and crystalline cone under light-adapted conditions compared to those under dark-adapted conditions. Under light-adapted conditions, pigment granules moved to and remained below the crystalline cone and were near the rhabdom. In contrast, under dark-adapted conditions, pigment granules moved to the distal end of ommatidia, near the cornea, and exhibited a more spatially distributed pattern. These results provide essential information for exploring the poorly understood sensory ecology of butterflies in the family Lycaenidae.