Abstract: Diurnal rhythm of adult behavior of the rice water weevil, Lissorhoptrus oryzophilus Kuschel, was watched and recorded at 30 min interval by single rearing separately in field from April 30th to May 4th, 2012. All behaviors were divided into five types, i.e., moving (MG), foraging (FG), resting without contacting water (ROCW), resting with contacting water (RWCW) and others (OT), and 7 200 behavioral data were collected and analyzed. The results showed that the major behaviors were ROCW, accounting for 47.83%, while MG was minimum, accounting for 5.64%. Diurnal time among various behaviors were significantly different (P<0.001). The peak of ROCW was recorded at 23:30 (72.67%), the lowest was recorded at 7:30 (14.67%). Both RWCW and FG had two peaks, occurring at 7:30 (75.33%) and 19:00 (37.33%), and 15:00 (26.67%) and 21:00 (18.00%), respectively. The peak of MG occurred at 17:00 (20.00%). The proportion of OT fluctuated from 1.33% to 18.67%. The results of the Mann-Whitney U test indicated that there were significant differences in ROCW, MG, FG and OT between day and night (P<0.001), but RWCW had no difference between day and night (P=0.834). The further analysis also showed that five behaviors had significant differences in forenoon, noon, afternoon and night during a day (P<0.001). ROCW and FG mainly occurred on the rice leaf, while MG mainly occurred in the water. However, the results of the Kruskal-Wallis H test confirmed that ROCW, MG and FG had marked spatial variation in different parts (P<0.001). RWCW, MG and OT were found in the water, but the fluctuation of RWCW was the biggest. The three behaviors had significant differences among different time periods within a day (RWCW and MG: P<0.001; OT: P=0.002). ROCW, MG and FG were found on the leaf, ROCW and FG were strongly regulated by time and their frequencies had significant differences among different time periods within a day (P<0.001). ROCW and MG were found in the stem and bottle wall or sealing gauze, however, the proportions of behaviors kept at a lower level. The behaviors of the rice water weevil were mainly found in the water and on rice leaf, the peak of behaviors in the water (81.33%) and the lowest frequency of behaviors on the leaf (12.00%) occurred at the same time (7:30), both showing rotation variation. These results suggest that both temporal and spatial variation could significantly influence the behaviors of the rice water weevil, and the effect of temporal variation is more significant than spatial variation.

Key words: Lissorhoptrus oryzophilus, adult, behavior, diurnal rhythm, rice