Abstract: Compound eye is the main vision organ of insect, which plays a significant role in their foraging, finding mate and habitat, learning, memory and so on. In this study, the external morphology and internal microstructure of the compound eyes of Harmonia axyridis ab. conspicua were observed by using scanning electron microscope and paraffin section. The results indicated that: (1) the compound eye is oval, and located on the lateral upside of the head. There is a nick on the compound eye, which is near to antennal socket. The surface of the ommatidia is smooth and not covered with corneal nipples. The compound eye of the female and male consists of 705 and 691 ommatidia, respectively. (2) The ommatidia located in the central region of the compound eye are typically hexagonal, while those located in the periphery of the compound eye are often of irregular, pentagonal, and even squarish shapes. (3) The ommatidium consists of corneal lens, crystalline cone, 8 retinula cells, rhabdom, basement membrane and pigment granules. The crystalline cone is composed of 4 cells. Among the 8 retinula cells, 6 cells are in the periphery and the other 2 are in the centre. (4) The microstructure of compound eye of H. axyridis ab. conspicua is significant different between dark and light adaptation. In light adaptation, most of the pigment granules are distributed between the crystalline cone and rhabdoms; the peripheral rhabdom is in ring form, and its inner and outer sides are covered with the pigment granules. In dark adaptation, the pigment granules move longitudinally and are distributed on the lateral upsides of the crystalline cone and rhabdoms; the peripheral rhabdoms twist appearing as irregular polygons, and only its outer sides are covered with the pigment granules. This study reveals that the compound eyes of H. axyridis ab. conspicua are of the type of apposition eye, and they adapt to the change of light and dark by the mechanism of pigment granules moving longitudinally and rhabdoms twisting.
 

Key words: Harmonia axyridis ab. conspicua, compound eye, ommitidium, external morphology, microstructure, light adaptation, dark adaptation