This study includes three models, the plant (wheat)model, the pest(the army-worm) model, and the predator (Calosoma chinense) model. By coupling the plant-pest-predator models and simulating day by day one is able to get the dynamic ET (Table 3) under various developmental stage of winter wheat and various densities of C. chinense. The result of this simulation shows that the earlier the armyworm appears, the smaller the value of ET; under the same developmental stage of wheat, ET increases with the increas...