Abstract: The spider, T. octomacuJatum, an important predator of rice hoppers, could attack 0.25-1.88 brown planthoppers (N. lugens) in a day. The functional response of the spider to N. lugens was simulated with Hoi ling's II and Sigmoid III type models in the laboratory. The functional response model became a typical Sigmoid III type when the space and complexity of the experimental arena increased. It is speculated that the population ratio between the spider and N. lugens in the field fluctuates with the density and age-structure,of the pest and the economic threshold for the control of the planthopper.