Selective predation of Delphastus catalinae (Horn) on Bemisia tabaci (Gennad-(ius)) and Tetranychus nr. Fijiensis
小黑瓢虫与两种猎物作用系统研究:选择捕食作用

Delphastus catalinae (Horn) (formerly known as Delphastus pusillus (LeConte)) (Coleoptera: Coccinellidae) is the most important predator of Bemisia tabaci (Gennadius), which has become a major pest in numerous crops all over the world. It was introduced into China in order to combat B. tabaci in 1996, and inhabited successfully from then on. During the course of our study, we noticed that besides B. tabaci, the ladybird could also consumed Tetranychus nr. fijiensis. In spring and autumn, B. tabaci and T. nr. fijiensis may infest greenhouse crops simultaneously. In order to facilitate future utilization for whitefly control in confined environments, selective predation of the female adult of D. catalinae on both eggs of B. tabaci and T. nr. fijiensis was studied in the one-predator-two-prey system, and the results showed that the female adult beetle had no preference to eggs of B. tabaci in the low total prey density and positive preference in the middle and high total prey density, and no preference to eggs of T. nr. fijiensis in all degrees of total prey density. The female adult beetle also showed different switching to eggs of B. tabaci in different degrees of total prey density, that is, no switching in the density of 150 eggs, and negative and positive switching in the density of 300 eggs and 600 eggs, respectively, however the beetle showed negative switching to eggs of T. nr. fijiensis in all degrees of total prey density. The total amount of prey and the amount of each prey captured by the female adult beetle were simulated, and the searching efficiency of the female adult beetle to the eggs of the two preys was also analyzed.