MONOTERPENES EMITTED BY THE LARGE PINE WEEVIL, HYLOBIUS-ABIETIS (L.) FEEDING ON SCOTS PINE, PINUS-SYLVESTRIS L

Attraction of the large pine weevil, Hylobius abietis (L.) (Coleoptera : Curculionidae) to pine logs was enhanced by the presence of weevils already on the logs. We investigated the volatiles emitted by insects feeding on host trees to determine the mechanism of the attraction. Ch emical analyses of the collected volatiles showed large amounts of mon oterpenes. There were no qualitative differences in the collections, b etween Scots pine alone and pine plus feeding weevils, nor between mal es and females, mated or virgin. Strong quantitative differences in mo noterpenes existed that were correlated to the surface of cut bark. El ectroantennograms (EAGs) were recorded on male and female antennae sti mulated by increasing doses of collected volatiles. EAGs for pine alon e and pine plus weevils at the same stimulus loading in (alpha + beta) -pinene gave superimposable curves. EAGs of male and female volatiles were also identical. These results suggest an attraction mediated by h ost plant allelochemicals rather than by an aggregation pheromone.