Behavioral Characteristics Of Empoasca Vitis, Toxoptera Aurantii And Their Natural Enemy, Erigonidium Graminicolum

This paper deals mainly with the effect of light, location, color and odor on behaviors of Empoasca vitis Gothe, Toxoptera aurantii Boyer and Erigonidium graminicolum Sundevall as well as the functional responses of E. graminicolum to T. aurantii.The phototaxis experiments on E. vitis and T. aurantii indicated that E. vitis had a strong preference to light, while T. aurantii didn't show any perference to it. In the test of their location selection, both E. vitis and T. aurantii preferred the upper part to the lower one. Six colors- red, yellow, green, blue, white and purple were employed to test their preference for color, and the result showed that T. aurantii were sensitive to red and yellow. Since tea shoots are often yellowish, its sensitivity to the color of yellow may imply that the insect would be dependent on the recognization of color when searching for young shoots. And when tea shoots were painted black, E. vitis preferred Cassia rotundifolia which is not its host plant, and although tea shoots painted black attracted less T. aurantii, it attracted much more tea aphids than C. rotundifolia.In the Y-tube olfactometer, E. vitis showed no significant preference to volatiles of tea shoots, while significantly more T. aurantii chose volatiles of tea shoots when tested against clean air. And the number of E. vitis attracted didn't reduce but the number of T. aurantii decreased evidently when tea shoots were sprayed with extractions from other plants which were not host plants of these two kinds of pests. The result demonstrated that olfaction played a minor role for E. vitis in orientation to host plant, while it was very important for T. auranti to search for its host.E. vitis and T. aurantii showed no preference between normal tea shoots and tea shoots damaged by E. vitis and T. aurantii.Both male and female E. graminicolum showed preference for light. The result suggested that lighted areas where prey densities are elevated provide cues used by the spiders to rank optimal foraging sites. The number of E. graminicolum stayed in higher patch was much bigger than those staying in lower patch. They exhibited no significant differences among the six colors provided in the experiment. It indicated E. graminicolum were not sensitive to color and they didn't use the cue of color of the host plant of their preys to choose habitat. In the Y-tube olfactometer, E. graminicolum showed no significant preference between odor of host plant of preys and air, odors of preys and air, mixed odors of preys and tea shoots and air. It indicated that E. graminicolum didn't make use of odor of preys and their host plant to search food.In the Y-tube olfactometer, E. vitis and T. aurantii showed no significant preference between odor of tea shoots and mixture of tea shoots and E. graminicolum. It indicated that E. vitis and T. aurantii didn't have the ability to decrease the predation risk through the strategy of decreasing the time of staying in the patch with high predation risk.The predatory functional responses of E. graminicolum to T. aurantii were also studied in the laboratory and the results showed that the functional responses of E. graminicolum to T. aurantii belonged to Holling' s II type. Intraspecific interference was found in the experiment. The predation rate of E. graminicolum decreased along with the increase of predator density. Mutual interference of prey and predator densities could reduce the searching efficiency of E. graminicolum, but had no impact on its preying process.