INNATE RESPONSES OF THE PARASITOIDS COTESIA-GLOMERATA AND C-RUBECULA (HYMENOPTERA, BRACONIDAE) TO VOLATILES FROM DIFFERENT PLANT-HERBIVORE COMPLEXES

To determine and compare innate preferences of the parasitoid species Cotesia glomerata and C. rubecula for different plant-herbivore comple xes, long-range (1-m) foraging behavior was studied in dual-choice exp eriments in a wind tunnel, In this study we tested the hypothesis that naive females of the specialist C. rubecula should show more pronounc ed preferences for different plant-herbivore complexes than females of the generalist C. glomerata. The herbivore species used were the pier ids Pieris brassicae, P. rapae, P, Napi, and Aporia crataegi and the n onhosts Plutella xylostella and Mamestra brassicae. All herbivore spec ies feed mainly on cabbage and wild crucifers, except Aporia crataegi, which feeds on species of Rosaceae, Both parasitoid species preferred herbivore-damaged plants over nondamaged plants, Neither C, rubecula nor C, glomerata discriminated between plants infested by different ca terpillar species, not even between plants infested by host- and nonho st species, Both parasitoid species showed preferences for certain cab bage cultivars and plant species, No differences were found in innate host-searching behavior between C, glomerata and C. rubecula. The trit rophic system cabbage-caterpillars-Cotesia sp. seems to lack specifici ty on the herbivore level, whereas on the plant level differences in a ttractiveness to parasitoids were found.