Comparative Studies On The Predation And Reproduction Of Orius Sauteri(Poppius)(Heteroptera: Anthocoridae) Comsuming Both Frankliniella Occidentalis (Pergande)(Thysanoptera: Thripidae) And Tetranychus Urticae Koch (Acari: Tetranychidae)

Western flower thrips (Frankliniella occidentalis (Pergande)) (Thysanoptera: Thripidae) is one of the very important invasive pests. Its'successful colonization in Beijing is directly related to the biological and ecological characteristics. An invasive species will be directly or indirectly affect the fluctuation of other biological populations after its'invading into the same habitat. Two-spotted spider mites (Tetranychus urticae Koch) (Acari: Tetranychidae) often coexist with thrips on vegetables, ornamentals and fruit trees. Both pests can affect each other's population dynamics. Orius sauteri (Poppius) (Heteroptera: Anthocoridae), as a predominant predatory natural enemy of many pests, plays an important role in suppressing the population of both thrips and spider mites. In this paper, kidney bean plants were used as host to examine the interactions among western flower thrips, two-spotted spider mites and Orius sauteri under laboratory conditions. The main results were as follows: 1. The prey preference of O. sauteri to different stages of western flower thrips and two-spotted spider mites and the interference of the prey density were confirmed. The prey preference of O. sauteri to different preys showed that under same prey density ratio both 5th instar nymphs and adults of O. sauteri prefer to feed on nymphs than on adults of F. occidentalis, whereas prefer to feed on adults than on nymphs or larvae of T. urticae. The second instar larvae of thrips were the most favorite for O. sauteri among the 5 stages of thrips and spider mites. The study of interference of prey density to the O. sauteri showed, at a fixed density of spider mites (60/19.63cm2), increasing thrips density from 10 to 60 significantly decreased the predation of spider mites by O. sauteri; However, at a same fixed thrips density, increasing spider mites density didn't decrease the predation on thrips. These results strongly indicated that F. occidentalis was a more suitable prey than T. urticae for O. sauteri.2. Life table parameters of experimental population of predator O. sauteri when reared on two different preys were confirmed.The results showed that the net reproductive rate (R0), the intrinsic rate of increase (γm), the mean generation time (T), the finite rate of increase (λ) and the doubling time (t) of O. sauteri feeding on the larvae of western flower thrips and female adults of two-spotted spider mites were: 27.86 and 14.16, 0.1485 and 0.1065, 23.22 days and 25.43days, 1.1589 d-1 and 1.1116 d-1, 4.668 days and 6.508 days, respectively. And it was showed that consuming thrips larvae benefited the population of O. sauteri more than preying on spider mites female adults.3. The numerical response of O. sauteri feeding on larvae of western flower thrips and female adults of two-spotted spider mites was positive type. When larvae of western flower thrips and female adults of two-spotted spider mites coexist with the same density, the total prey density was 20, 40, 60, 80 and 100, the prey consumption and fecundity of O. sauteri's female adult increased with the prey density.