RESPONSE ON THE GROUND OF BARK BEETLE AND WEEVIL SPECIES COLONIZING CONIFER STUMPS AND ROOTS TO TERPENES AND ETHANOL

Responses of three Hylastes species, Dryocoetes autographus, and two H ylobius species to terpenes and ethanol were studied in field experime nts on clear-cut forest sites in Sweden using baited ground traps. Alp ha-Pinene alone did not attract any of the six species. A terpene blen d (spruce turpentine consisting mainly of alpha-pinene, beta-pinene, a nd 3-carene) attracted Hylastes cunicularius, H. brunneus, and Hylobiu s abietis in some experiments, but not in others. The attractiveness o f ethanol also varied; the only species consistently attracted was H. abietis. Baits containing both terpenes and ethanol, particularly the combination of spruce turpentine and ethanol, were attractive to all s pecies except Hylobius pinastri. In H. abietis, the terpene plus ethan ol/ethanol catch ratios increased during early summer. Seasonal differ ences in catch levels were observed in H. cunicularius and H. abietis. The addition of alpha-pinene reduced the attractiveness of the combin ation of spruce turpentine and ethanol to H. cunicularius, H. opacus, and D. autographus. The differences in response to the volatiles betwe en species are probably related to differences in reproductive behavio r and host preferences.