Flying Beetles Respond as Moths Predict: Optomotor Anemotaxis to Pheromone Plumes at Different Heights

The current level of understanding of orientation mechanisms used by flying insects responding to pheromone sources, based almost entirely on studies of moths and flies, allows clear predictions to be made of how other, hitherto little-studied insect taxa, such as beetles (Coleoptera), should behave if the same mechanisms are used. Results are presented of the first test of such set of predictions, the effect of flight height on ground speed, on a beetle, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae). The beetle P. truncatus flew upwind toward the source of horizontal pheromone plumes and responded to the movement of visible patterns on the floor of a sustained flight tunnel. Beetles flying at a greater height from the floor were less responsive to moving floor patterns. The flight speeds of P. truncatus increased with flight altitude, as found with moths, suggesting that they use orientation mechanism similar to those of moths.