| In this dissertation, the interactive system of Delphastus catalinae (Horn), its preys and competitor was studied, including comparison between alternative preys and natural prey consumed by D. catalinae; the system of D. catalinae and its preys; morphology comparison between D. catalinae and its competitor Serangium japonicum Chapin; biology, ecology and predation of S. japonicum; and also the interspecies competition between D. catalinae and S. japonicum.1. Besides whitefly pests, D. catalinae could also feed on two species of alternative preys: Tetranychus nr. fijiensis and Myzus persicae (Sulzer). In order to investigate the influence of alternative preys on the ladybird, comparison between its alternative preys and natural prey Bemisia tabaci (Gennidius) was studied in the laboratory, and the results showed that the beetle could not oviposit when feeding exclusively on M. persicae, but the adult longevity wasn't significantly changed compared with those feeding on natural prey. When feeding on T. nr. fijiensis, the beetle could oviposit and also finish its life history, without significant difference in the adult longevity compared with those feeding on its natural prey, but with longer developmental duration and higher mortality in each stage than those feeding on natural prey. Compared with those feeding on its natural prey, the duration of pre-oviposition of the beetle prolonged, the total egg production and the mean egg production per day decreased, without significant difference in sex ratio, rate of oviposition and oviposition period. The indices of population growth and the innate capacity for increase of the ladybird were 8.85, 0.0658 for feeding on T. nr. fijiensis and 55.38, 0.1905 for feeding on B. tabaci, respectively.2. In the system of D. catalinae and its preys, single predator-single prey system and single predator-two preys system were studied. The results showed that in the single predator-single prey system of D. catalinae and T. nr. fijiensis, the adult female of D. catalinae had significantly different feeding preference in selecting the stages of T. nr. fijiensis, with the most preference of the eggs followed by larva, protonymph, deutonymph and adult respectively. The functional responses of 2-4 instar larvae and adult of D. catalinae to eggs of T. nr. fijiensis belonged to Holling II type, and the searching efficiency of theadult female of D. catalinae declined with increase of its density. The relationship between searching efficiency (E) and the adult ladybird density (P) was simulated as E = 0.3337 p-0.4286 by Hassell & varley's model E=QP-m and as E = 0.3110T / [ 1+0.2158x(P-1) ] by Beddington's model E=aT/[l+btw(P - 1)], respectively, but Hassell &Varley's model could describe the relationship better than Beddington's model. The relationship among searching efficiency (E), the prey density (N) and the adult ladybird density (P) was simulated as E = 0.3 1 10 / (0.7842 + 0.000404 N + 0.21 58 P) by Beddington's model E = aT / [ 1 + athN + btw (P - 1) ], i.e. the searching efficiency declined when the adult ladybird and the prey densities increased. In the single predator-two preys system, the selective predation of the adult female beetle to both eggs of B. tabaci and T. nr. fijiensis was discussed when two preys coexisted. The adult female beetle showed no preference to eggs of B. tabaci in the lower total prey density and positive preference in the middle and higher total prey density, and no preference to eggs of T. nr. Fijiensis in all degrees of total prey density. The adult female beetle also showed different switching to eggs of B. tabaci in different degrees of total prey density, but showed negative switching to eggs of T. nr. fijiensis in all degrees of total prey density. The functional responses of the adult female beetle to both eggs of the two preys belonged to type I or III, which was mainly caused by the switching behavior. Searching efficiency of the adult female beetle to both eggs of the two preys was also analysed. The total amount of prey captured...
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