Fine Structure of the Compound Eyes of Longicorn Beetles (Coleoptera : Cerambycidae)

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Abstract
The compaound eyes of seven species of longicorn beetles were opbserved by electron microscope, and the relationship between the activity and the structure was considered. Changes ao organellas during light-dark adaptation were also observed on one of these species. Corneal nipples were found in Leptura. Two central retinula cells were surrounded by six peripheral cells. Each cell contributed to the rhabdom formation, but the two central cells apparently formed one rhabdomere. The configuration of the rhabdom and the orientation of its microbilli in the transverse plane were variable according to species and activity. In diurmally active species, especially in the group active under bright sunshine, peripheral rhabdomeres were small and separated from neighboring ones. However, in nocturnally active species, rhabdoms were large. The ratio of rhabdom to retinula cells in the transverse plane was higher than 48% in nocturnal and less than 31% in diurnal species. Both primary and secondary pigment cells contained pigment grains which varied in diameter according to speces but, as a whole, teh former larger grains than the latter. In Paraclytus, palisades appeared at the basel part of rhabdomic microvilli, and were especially conspicuous in central cells during dark adaptation. In the light-adapted state, however, they almost disappeared.