Light versus pheromone‐bearing wind in the control of flight direction by bark beetles, Scolytus multistriatus

A wind tunnel lit from above was used to measure the relative effectiveness of light as opposed to pheromone‐bearing wind in directing the flight of male S.multistriatus. Upward flight in the tunnel was overridingly phototactic not geotactic, while horizontally upwind flight toward the pheromone source was anemotactic not chemotactic, since the pheromone concentration was uniform in the tunnel. The flight tracks of newly‐emerged unfed and previously unflown beetles were preponderantly upwards and downwind; the longer the beetles had spent in flight activity beforehand, the more of them flew upwind.