Selective predation of \%Cantheconidea furcellate \% Wolff on the 2nd instar larvae,4th instar larvae and the 6th instar larvae of \%spodoptera litura\% in coexistence of three prey\|age types was studied.The quadratic function models,describing the relationship between the number of prey attacked and the densities of predator and its preys,were established by the rotational composite design of quadratic regression.Based on the predation models,the selective preying ratios could be calculated under the comb...