Effects of tea plant volatiles on foraging behavior of Xysticus ephippiatus Simon

Although the attractiveness of emitted plant volatiles under attack by herbivores has been demonstrated in tritrophic sys-tems, how these semi-chemicals affect foraging behaviors of crab spiders remains poorly understood. We therefore examined whether the saddle crab spider, Xysticus ephippiatus Simon, showed preferences to volatiles emitted from the most recent prey-consumed fields. Such fields consisted of two chambers or foraging patches — a control chamber of undamaged tea leaf and a stimulus chamber of Ectropis obliqua-damaged tea leaf. We collected and identified the volatiles emitted from different treated tea leaves by solid phase micro-extraction-GC-MS (SPME-GC-MS). The results showed that E. obliqua-damaged tea leaves released an average of about 31 volatiles. The main constituents of the volatiles were 12 green leaf volatiles (Z)-3-hexenal, (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, 2-ethyl-1-hexenol, (Z)-3-hexenyl butyrate, (Z)-3-hexenyl iso-butyrate, (E)-2-hexenyl butyrate, (Z)-3-hexenyl 2-methyl butyrate, (Z)-3-hexenyl 3-methyl butyrate, (Z)-3-hexenyl hexanoate and (E)-2-hexenyl hexanoate, 9 terpenoids (E)-β-ocimene, (Z)-linalool oxide, linalool, nonanal, decanal, DMNT, 1-nitro-2-phenyl ethane, (E,E)-α-farnesene and (Z)-6,10-dimethyl-5,9-undecadien-2-one, 4 aromatic compounds benzyl alcohol, phenylethyl alcohol, Indole and benzyl nitrile and 6 unknown compounds. No volatiles were, however, detected from undamaged tea leaves. X. ephippiatus females and males were not preferential to undamaged leaves or E. obliqua-damaged leaves as first choice (χ²2=0.26, P=0.612, n=35 for female; χ²=0.71, P=0.398,n=35 for male). The frequencies of the females moving into different odor sources were similar (mean=3.37±0.18 for E. obliqua-damaged leaves and mean=3.43±0.15 for undamaged leaves). Also the frequencies of the males moving into different odor sources were similar (mean=3.86±0.21 for E. obliqua-damaged leaves and mean=3.66±0.20 for undamaged leaves). The residence time of females and males in foraging patches with E. obliqua-damaged leaves was significantly longer than that in foraging patches of undamaged leaves. The results suggested that tea leaves damaged by E. obliqua emitted more volatiles than undamaged leaves and X. ephippiatus exploited these indirect cues to make patch residence time decisions. The ecological importance of volatiles on forag-ing behaviors of crab spiders was discussed also in the paper.