Upwind flight orientation to pheromone in western pine beetle tested with rotating wind vane traps

In the first trap design, a rotating windvane was connected to a 30 × 30 × 30-cm "square box" sticky trap enclosing a synthetic pheromone source (exo-brevicomin, frontalin, and myrcene) at the windvane's rotation axis. A second design used the windvane attached to two tubular (19-cmdiam. × 30-cm) sticky traps each suspended 120 cm from the same pheromone source and opposingly aligned "downwind" and "upwind" of the windvane. Significantly more beetles of each sex ofDendroctonus brevicomis LeC. (Coleoptera: Scolytidae) were caught on the downwind side compared to the upwind side of the square-box design. Even larger differences in catch, four times more males and 3.4 times more females, were found on the downwind tubular trap compared to the upwind one. The windvane trap design provides rigorous evidence that insects, especially bark beetles, orient upwind to pheromone sources (from at least 1.2 m downwind until reaching the source).