Abstract: 【Aim】 The ultrastructure of the compound eye of Ectropis grisescens adults and its changes upon light/dark adaptation were observed to explore its light tuning mechanism. 【Methods】 The external parameters including the ommatidial number, interommatidial angle of ommatidium, ommatidial diameter and radius of curvature of ommatidium of the compound eye of E. grisescens adults were determined by using ultra depth of field microscopye, and the ultrastructure of adult compound eyes was observed by using histological sections, optical microscope and transmission electron microscope. The changes of crystalline cone structure and displacement of pigment particles in the compound eye of E. grisescens adults after adaption in light and dark environments, respectively, for 2 h were observed by using optical microscope. 【Results】 The compound eyes of E. grisescens adults are hemispherical, and each compound eye consists of about 2 502±105 ommatidia in females, and 3 123±78 ommatidia in males. Each ommatidium consists of a dioptric apparatus made up of a cornea, a crystalline cone and a clear zone, and a photosensitive layer made up of 15 retinal cells. Two primary pigment cells encase the crystalline cone and extend from the proximal part of the cornea to the distal part of the retinula cell nuclear zone. The periphery of ommatidium is surrounded by six secondary pigment cells, which extend from the proximal part of the cornea to the basement membrane. In the clear zone, 14 retinal cells aggregate into a bundle (non-rhabdom), the distal part of which is connected with the end of the crystalline tract, forming a closed rhabdom in the photosensitive layer and extending to the 15th retinula cell (basal retinula cell). During light/dark adaptation, the compound eyes adjust the light input mainly by the longitudinal displacement of pigment particles and the opening and closing of crystalline cone to adapt to the change of light intensity. 【Conclusion】 The compound eye of E. grisescens adults belongs to the refracting superposition eye, and the rhabdom is the 14+1 pattern. The movement of pigment particles is an important mechanism for the compound eyes of E. grisescens adults to adapt to the change of light intensity.

Key words: Ectropis grisescens, superposition eye, external morphology, ultrastructure, light tuning