Abstract: In the predator-prey system,eating-weariness may be caused by the fullness of predators.Ifthe coefficient of eating-weariness b,a constant of linear equation (Th=Th′+bN),is intro-duced into Holling's disc equation,an improved disc equation will be then obtained: N=a′TN/(1+a′(Th′+bN)N) Th′ is pure handling time without eating-weariness;b is coefficient of eating-weariness,whi-ch may be considered as an index of the abilities of a natural enemy.In the present paper,it was proved that the improved disc equation was better than Holling's original equationbased on studies on the functional response of a ladybird preying upon aphids and an inch-neumonid wasp parasitizing on a ladybird larva.

Key words: Root exudates, Phenolic acid substances