Influence of wind on the spring flight of Trypodendron lineatum (Olivier) (Coleoptera: Scolytidae) in a second-growth coniferous forest.
The mark-recapture technique was used to examine the spring flight dispersal of Trypodendron lineatum in an even-aged second-growth coastal forest in British Columbia. Pheromone-baited traps were placed in circular trap-lines at distances of 5-500 m from a central release location to examine the relationship between wind direction and beetle catches in traps arranged around the release point, and to evaluate beetle catch characteristics when distances to baited traps were varied. A total of 29 800 marked beetles was released in three experiments. Upwind flight was most strongly exhibited at 5 m, with an upwind trend at 25 m, and no consistent flight pattern at 100 m, when wind movement was significantly directed. When the closest attraction was 100 m from the release point, beetles were caught uniformly in all directions, indicating that flight was non-directional with respect to wind, for light wind speeds. Catches in 500-m traps tended to be downwind, thus beetles capable of flying that distance were those that were flying with the wind. Equal numbers of beetles were captured at 5, 25 and 100 m despite increased intertrap spacings of 8, 20 and 32 m, resp. A higher proportion of beetles was captured at 100 m when close-range traps at 5 and 25 m were not present.