Abstract: 【Objective】 The objective of this study is to evaluate the potential regulation capacity of Chrysopa pallens to Bemisia tabaci, and analyze the function response, searching rate and relative predatory behaviors of C. pallens on B. tabaci egg, nymph and pupa in lab conditions.【Method】 Different prey densities of egg, nymph and pupa of B. tabaci were set up as different treatments for evaluating predatory capacity of 3rd instar larva C. pallens. The net aggregation of prey consumed and prey consumed ratio in each density were recorded and analyzed. Furthermore, the predatory period was classified into different independent behavior events and evaluated each event in the way of occurrence frequency and ratio of each behavior event to the total duration of predation. The description of each event was also executed at the same time. 【Result】 The results showed that the function response of C. pallens 3rd instar larva on B. tabaci egg, nymph and pupa were fitted to Holling II & III formulas. In lab controlled conditions, the predatory capacities of C. pallens on B. tabaci egg, nymph and pupa increased with the increasing prey density. The instantaneous attacking rate was increased with the increasing of target development stages, and the variation of dealing duration was nymph ＞ pupae ＞ egg. On the contrast, the best searching density was the lowest in nymph treatment. Furthermore, the evaluation of searching rate showed that the searching rate of C. pallens on B. tabaci increased with the increasing of target development stages. When C. pallens preyed egg and nymph, the percentage of walking and searching behavior were the most and second. But in pupa treatment, the searching behaviour was the first place and the predation was the second. Similarly, the frequency of each behavior was shown significant differences in predation courses. 【Conclusion】The present study demonstrated that the predatory capacity of C. pallens larva to B. tabaci egg, nymph and pupa increased with prey density increasing without any density restriction. The analysis of occurrence frequency and time spend ratio of each behavior event showed significant differences when predator preyed different kinds of prey. The results showed that B. tabaci pupa is the favorite prey of C. pallens larva at low prey density level.

Key words: Chrysopa pallens, Bemisia tabaci, function response, predatory behavior