The dwarf spider is of non-compensative predation on cotton bollworm in cotton field. But the'population density variation of the spider which will be influenced by cotton bollworm is not too large. The functional response of the dwarf spider to cotton bollworm can be described by using Holling(1959a)'s equation. The different conditions of experiment will produce the different effects on the estimation of parameters of the functional response. The best prey size for feeding of the adult female spider is th...