Study On Microstructure Of The Compound Eye And Phototactic Behavior Of Harmonia Axyridis Pallas

Compound eye is the main vision organ of insect, which play a significant role in their foraging, finding mate and habitat, learning, memory and so on. In the paper, the external morphology of the compound eyes of Harmonia axyridis ab.conspicua Fald and Harmonia axyridis ab.succinea Hope and internal microstructure of Harmonia axyridis ab.succinea Fald were observed by using scanning electron microscope and paraffin section. The phototaxis behavior of Harmonia axyridis Pallas response to spectral sensitivity were investigated. The results were as follows: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 isn′t covered with corneal nipples. The compound eye of the female and male of Harmonia axyridis ab.conspicua Fald consists of 705 and 691 ommatidia. The compound eye of the female and male of Harmonia axyridis ab.succinea Hope consists of 670 and 663 ommatidia, respectively. 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. There are some interfacetal hairs randomly distributed , which are different in shape and size.2. 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. In 8 retinula cells, 6 cells are in the periphery and the other 2 are in centre.3. The microstructure of compound eye of H.axyridis ab.conspicua is significant difference between dark and light adaptation. In light adaptation, most of the pigment granules distribute between the crystalline cone and rhabdoms. The peripheral rhabdom is ring , and it﹐s inner and outer are coverd with the pigment granules . In dark adaptation, the pigment granules move longitudinally and distribute on the lateral upsides of the crystalline cone and rhabdoms. The peripheral rhabdom twiste , irregular polygon and only it﹐s outer is coverd with the pigment granules. This paper revealed that the type of the compound eye of H.axyridis ab.conspicua was apposition eye, and it adapts to the change of light or dark by the mechanism of pigment granules moved longitudinally and rhabdom twisted. 4. Both the monochromatic lights of different wavelengths and white light could induce phototactic behavior reactions of Harmonia axyridis Pallas with different levels. According to the phototactic rate, several peaks appeared in their spectral behavior response curve, the ultra-violet light of the wave length 360 nm elicited the strongest behavioral response of the female (25.0%), and the secondary in 524nm (green) and 420nm(blue).The prmiary peak in 360nm (ultra-violet) is the highest response rate of phototaxis of the male (20.0% ), and followed by the secondary in 524nm (green), and the rest in 420nm(blue). No significant differences were observed between the sexes.