Journal of Chemical Ecology, Vol. 26, No. 6, 2000 0098-0331 / 00 / 0600-1433$18.00 / 0  2000 Plenum Publishing Corporation 1433 IDENTIFICATION OF VOLATILE POTATO SESQUITERPENOIDS AND THEIR OLFACTORY DETECTION BY THE TWO-SPOTTED STINKBUG Perillus bioculatus BERNHARD WEISSBECKER, 1 JOOP J. A. VAN LOON, 1, * MAARTEN A. POSTHUMUS, 2 HARRO J. BOUWMEESTER, 3 and MARCEL DICKE 1 1 Laboratory of Entomology, Wageningen University P.O. Box 8031, 6700 EH Wageningen, The Netherlands 2 Laboratory of Organic Chemistry, Wageningen University Dreijenplein 8, 6703 HB Wageningen, The Netherlands 3 Institute for Agrobiology and Soil Fertility (AB) Wageningen University and Research Centre P.O. Box 14, 6700 AA Wageningen, The Netherlands (Received July 1, 1999; accepted February 6, 2000) Abstract—The predaceous stinkbug Perillus bioculatus is attracted towards volatiles emitted by damaged potato plants. Whereas mechanically damaged plants lost attractiveness 1 h after damage was inflicted, attraction was long-lasting when the plants were damaged by Colorado potato beetles Leptinotarsa decemlineata, a prey of P. bioculatus. A range of sesquiterpe- noids was previously shown to be induced upon beetle damage. In order to evaluate the potential role of sesquiterpenoids in the attraction response, volatiles from damaged potato plants were collected and analyzed with GC-MS and GC-EAG. The antennae of P. bioculatus responded to b-caryophyllene, a-humulene, (E )-b-farnesene, ( )-germacrene D, and germacrene D-4-ol. Two sesquiterpenes that coeluted, a-zingiberene and bicyclogermacrene, together also elicited olfactory responses of P. bioculatus, whereas the individual compounds did not. The response of P. bioculatus to a variety of sesquiterpenes at low dosages suggests a role for these compounds in prey detection of this stinkbug. Key Words—Hemiptera, Pentatomidae, Perillus bioculatus, predator electro- antennography, EAG, GC-EAG, tritrophic interactions, sesquiterpenes, herbi- vore-induced plant volatiles. *To whom correspondence should be addressed.