LAUSR

The minute pirate bug Orius sauteri (Poppius) (Heteroptera: Anthocoridae) is a major natural enemy of micro-pests and is expected to be an effective pest-control agent in Asia. Recently, the violet wavelength has been found to attract several natural enemies, and we proved that violet illumination can increase the O . sauteri population and decrease the pest populations on crops. To optimize this attraction strategy for natural enemies, knowledge of their daily activity rhythm is indispensable. In this study, we examined the daily distribution of O . sauteri activity and determined the lighting time appropriate for selective attraction. Under artificial light–dark cycles, O . sauteri displayed a typical diurnal rhythm that peaked from 9 to 12 h after light-on and declined after light-off, regardless of the photoperiod. A similar activity rhythm was confirmed under natural light. Importantly, the activity remained for around 2 h after sunset, even in complete darkness. Considering the diurnality of micro-pests, we conclude that the most efficient lighting time for the selective attraction of this natural enemy to crops is during the 2 h after sunset.