Secondary attraction in the western balsam bark beetle, Dryocoetes confusus (Coleoptera: Scolytidae).
Evidence for secondary attraction in adults of Dryocoetes confusus Sw. was obtained in laboratory bioassays and field experiments in British Columbia in 1980. Both sexes showed positive responses to volatiles of the food-plant alpine fir (Abies lasiocarpa), indicating that primary attraction was probably important in host selection. Male beetles initiated attack, and within 6 h produced an aggregation pheromone which was present in frass and in pentane extracts of the abdomens of males excised from logs. Both sexes responded to the pheromone. Abdominal extracts of unmated males which had bored into host bark for 14 days were still attractive. Pheromone production was induced by exposing males to host resin volatiles. Mating had no effect on male attractiveness, but induced females to produce an antiaggregation pheromone which, in laboratory bioassays, at least partly inhibited response to male attractant. The attractive volatiles from male-infested logs were successfully captured on Porapak Q.