Abstract: In order to investigate the roles of volatiles from host plants in the process of Hippodamia variegata (Goeze) searching for preys, the behavioral responses of the lady beetle adults to volatiles from Aphis gossypii Glover, intact plants, aphidplant complex and aphidinfested plants were observed with a Y-tube olfactometer. The results showed that the adults were significantly attracted to volatiles from high-density (≥700 individuals/L) aphids, aphid-plant complex, and aphid-infested Cucumis sativus plants (aphid density≥400 individuals/pot) and Cucurbita pepo var. medullosa plants (aphid density≥200 individuals/pot), while not to volatiles from low-density (≤500 individuals/L) aphids and the intact plants. Dynamic headspace collection was used to extract volatiles from the intact plants, aphid-plant complex and aphid-infested plants, respectively, and the extracted volatiles were analyzed by gas chromatography-mass spectrometry (GC-MS). Eight, twelve and eighteen components were identified from the extracts of the intact plants, aphid-infested plants and aphid-plant complex of C. sativus, respectively. The main components include 1-octadecene, ［E］-5-eicosene, hexadecane and heptadecane, and aphid-induced components are p-xylene, 1,2-dimethy-benzene, tridecane, 1-tetradecene, α-farnesene, cedrol, octadecane, hexacosane and other seven unknown components. Eleven, eighteen and twenty components were identified from the extracts of the intact plants, aphid-infested plants and aphid-plant complex of C. pepo var. medullosa, respectively. The main components include α-caryophyllene, 1-octadecene, hexadecane and heptadecane, and aphid-induced components are ethylbenzene, p-xylene, m-xylene, α-pinene, tetradecane, longifolene, α-caryophyllene and other two unknown components. The results lay a necessary foundation for further research on the effective components to attract lady beetles.

Key words:  Hippodamia variegata, Aphis gossypii, Cucumis sativus, Cucurbita pepo var. medullosa, behavioral response, volatile