Abstract: The method of rotational composite design of quadratic regression is used to establish mathematical models of predatory capacity in the coexistent system of three predatory natural enemies and two insect pests in paddy field. Under the system, predators prey mainly on white-backed rice planthopper.When coexist with 4th instar larva of white-backed rice planthopper and 3rd instar larva of rice leafroller, they also prey to a certain amount on the latter, the predation sequence is Paederus fuscipes>Pirata subpiruticus>Oedothorax insecticeps. Increase of the density of planthopper significantly reduces the predation on larva of rice leafroller, but increase of the density of the latter has little influence on the amount of planthopper being preyed.

Key words: multi-objective location-allocation (LA) model, spatial location selection, urban park, Shenyang