【Background】Serangiella sababensis Sasaji and Axinoscymnus apioides Kuznetsov and Ren are two dominant predatory ladybird beetles of whitefly pests, which were introduced from Southeast Asian years ago. Their effectiveness against the target pest, however, is not known in detail. 【Method】The time allocation and predation level when hunting for younger and older instar Bemisia tabaci nymphs were investigated in the laboratory. 【Result】With the increasing larval instars, the time spent on prey handling and rest decreased while that on searching increased in both predators. The prey handling times of S.sababensis larvae were significantly longer than that of A.apioides, and the level of predation was also higher than in A.apioides, regardless of B.tabaci instar. When comparing adults, the prey handling time by S.sababensis was higher than that in A.apioides, whereas the level of predation on B.tabaci was significantly lower than that of A.apioides.【Conclusion and significance】The both predatory ladybirds have large potential in whitefly control, but their time allocation are different. Therefore, different species of ladybird beetles should be released in the field according to the occurrence period of whitefly.