HOST MICROHABITAT LOCATION BY STEM-BORER PARASITOID COTESIA FLAVIPES - THE ROLE OF HERBIVORE VOLATILES AND LOCALLY AND SYSTEMICALLY INDUCEDPLANT VOLATILES

The origin of olfactory stimuli involved in the host microhabitat loca tion in Cotesia flavipes, a parasitoid of stem-borer larvae, was inves tigated in a Y-tube olfactometer. The response of female C. flavipes t owards different components of the plant-host complex, consisting of a maize plant infested with two or more larvae of the stem borer Chile partellus, was tested in dual-choice tests. The concealed lifestyle of the stem-borer larvae did not limit the emission of volatiles attract ive to a parasitoid. A major source of the attractive volatiles from t he plant-host complex was the stem-borer-injured stem, including the f rass produced by the feeding larvae. Moreover, the production of volat iles attractive to a parasitoid was not restricted to the infested ste m part but occurs systemically throughout the plant. The uninfested le aves of a stem-borer-infested plant were found to emit volatiles that attract female C. flavipes. We further demonstrate that an exogenous e licitor of this systemic plant response is situated in the regurgitate of a stem-borer larva. When a minor amount of regurgitate is inoculat ed into the stem of an uninfested plant, the leaves of the treated pla nt emit volatiles that attract female C. flavipes.