Abstract: Results from a behavioral study by using a four-armed olfactometer (Vet et al, 1983) showed that Mate and apterous virginopara of Aphis glycines were clearly attracted or arrested by volatiles from Glycine max, its secondary hostplant, and Rhamnus davurica, its primary hostplant. The attractiveness of G.max was greater than that of R. davurica. Chemical analysis indicated that there is some difference in the volatile profiles between these two plant species. The volatiles from two nonhost plant species Gossypium hirsutum and Cucumis sativa, which are the most suitable hostplants of another aphid A. gossypii closely related to A. glycines, werefound to be neutral. However, the odors of Luffa cylindrica and Cucurbita peposignificantly repelled the Mate virginopara of A. glycines. Thus, the olfactory response of A. glyeines to these host and nonhost plants implies the evolutionary transition of A. glycines in hostplant specificity. Blending the odors from nonhost plants Gossypium hirsutum, Luria cylindricaand Cueurbita pepo with the attractive odor of hostplant G. Max blocked the attraction of the latter to the alate virginopara of A.glycines. It thus appeared that attraction of host plant to aphids can be disrupted by the presence of nonhost plant volatiles which have presumably masked the host plant odor and the lack of attraction of the blended odors is caused by the change in volatile prolife.

Key words: Aphis glycines——olfaction——plant volatiles——electroantennogram