External Morphology and Microstructure of the Compound Eye of Anomala Corpulenta Motsehulsky (Coleoptera: Rutelinae)

In the current study, the external morphology and microstructure of the compound eyes of the scarab beetle Anomala corpulenta Motschulsky (Coleoptera: Rutelinae) were examined, and the regulatory mechanisms of light absorption were preliminarily identified. According to observations using electron microscopy and optical microscopes, the thickness of cornea of the compound eye was >50 μm, which is thicker than found in most insect species (<10 μm) and likely to provide protection to the eye when the insect is moving through the soil. The compound eyes of A. corpulenta are superposition eyes with a ‘clear-zone’, which is characterized by the migration of secondary iris and membrane pigment granules upon light/dark adaptation, the migration of basement membrane pigment particles from the proximal to distal ends of the eye, and the migration of secondary iris pigment granules into the clear-zone under light adaptation, which prevents light from being received during daytime. By contrast, the screening pigment granules were collectively clustered in distal interommatidial spaces around the cone and there was a basement membrane distribution of pigment granules in the proximal part of the eye, which would enable the eye to react to weak light levels.