Several pest species are known to have an orienting response to visual contrasts of light and dark. To evaluate the effect of visual contrasts on trapping the minute pirate bugs Orius spp（. Hemiptera: Anthocoridae） on blue sticky sheets, the number of trapped Orius spp. was compared among traps using white-edged, black-edged, and edgeless blue sticky sheets（ IT sheet, Idemitsu Kosan, Tokyo, Japan）. In the present study, 10 cm×10 cm blue sticky sheet was taped with 12 cm×12 cm white and black plastic sheet with a thickness of approximately 0.2 mm to create visual contrast. During the 7 days of field experiments with two replications in two different soybean fields, 10 blue sticky traps were fixed on a pole using two bulldog clips; the traps were randomly arranged and set at the canopy height of soybean plants. The number of Orius spp. trapped was significantly high in white-edged blue sticky traps, followed by edgeless and black-edged traps in two soybean fields. In total, 54 and 162 adults of O. sauteri and O. minutus were trapped, respectively, and 262 adults could not be identified by molecular identification. On comparing the number of trap captures on the edge and central areas, we found that a significantly higher number of bugs were captured at the edge area than at the central areas of white-edged and edgeless traps. For white-edged and edgeless traps, the ratio of trapped bugs between the edge and center did not significantly differ. Spectrum reflectance of traps indicated that the white-edged trap exhibited higher spectrum reflectance at wavelength of 400-780 nm than those of edgeless and black-edged traps. Spectrum reflectance of the edgeless trap was slightly higher than that of the black-edged trap. These results suggested that the increased number of Orius spp. trapped on white-edged blue sheets was not due to visual contrasts, but due to the increased brightness of these traps. Our results will be applied to provide an effective trapping method for monitoring Orius spp.
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