Seasonal Dimorphism in the Compound Eye Morphology of Scythris sinensis (Felder & Rogenhofer, 1875) (Lepidoptera: Scythrididae)

Scythris sinensis (Felder & Rogenhofer) is a diurnal moth characterized by its distinct spring and autumn forms. In our study, we analyzed the compound eye morphology of both forms utilizing scanning electron microscopy. The eyes are ellipsoidal and symmetrical, consisting of hexagonal ommatidia characterized by convoluted folds but lacking corneal nipples. We found that female moths have slightly larger compound eyes than males. Our counts of ommatidia indicate that males emerging in autumn (589–675) typically possess a higher number than males emerging in spring (492–698). This finding suggests an adaptation specific to the autumn period, potentially enhancing visual search efficiency in response to seasonal light variations and a constrained reproductive schedule. This research provides a foundational understanding of the visual behavior of S. sinensis concerning photoreception and phototaxis.