Visual acuity of Empoasca onukii (Hemiptera, Cicadellidae)

SIMPLE SUMMARY: Empoasca onukii, a small hemipteran insect, is a serious pest of tea plants. Visual cues play an important role in habitat localization of adult E. onukii. In this study, we found that an acute zone exists in the compound eyes of adult E. onukii. A structural trade-off of the compound eye ensures that E. onukii has low-resolution vision (approximately 0.14 cycles per degree). ABSTRACT: Empoasca onukii is a common tea plant pest with a preference for the color yellow. Past work has shown that host leaf color is a key cue for habitat location for E. onukii. Before studying the effect of foliage shape, size, or texture on habitat localization, it is necessary to determine the visual acuity and effective viewing distance of E. onukii. In this study, a combination of 3D microscopy and X-ray microtomography showed that visual acuity did not significantly differ between females and males, but there were significant differences in the visual acuity and optical sensitivity among five regions of E. onukii’s compound eyes. The dorsal ommatidia had the highest visual acuity at 0.28 cycles per degree (cpd) but the lowest optical sensitivity (0.02 μm(2)sr), which indicated a trade-off between visual resolution and optical sensitivity for E. onukii. The visual acuity determined from the behavioral experiment was 0.14 cpd; E. onukii exhibited low-resolution vision and could only distinguish the units in a yellow/red pattern within 30 cm. Therefore, visual acuity contributes to the limited ability of E. onukii to distinguish the visual details of a distant target, which might be perceived as a lump of blurred color of intermediate brightness.