VISUAL FEEDBACK IN THE CONTROL OF PHEROMONE-MEDIATED FLIGHT OF HELIOTHIS-VIRESCENS MALES (LEPIDOPTERA, NOCTUIDAE)

Male Heliothis virescens (F.) (Lepidoptera: Noctuidae) were made to fl y into a uniformly white and translucent tube within a large wind tunn el while responding to sex pheromone. Different visual patterns placed within the tube greatly affected the ability of the male moths to mai ntain upwind progress or remain oriented to the wind while in contact with the plume. Over 89% of males attempting to fly through a blank tu be, lacking visual patterns, became disoriented, the males gaining or losing altitude and repeatedly hitting the sides of the tube. Patterns of 20-40 dots placed on the sides of the tube at or slightly above pl ume level resulted in high levels of sustained upwind flight (47-74%) relative to patterns placed directly below (30-40%), directly above (3 5%), or slightly below the level of the flight path (26-44%). Optimal upwind progression in pheromone-responding males occurred when image m otion could be resolved both transversely (T), orthogonally to the lon gitudinal axis of the body relative to the horizontal plane of the env ironment, and longitudinally (L), along the body axis. Even very spars e patterns (single rows of dots) could elicit high levels of sustained upwind flight (53-63%) when positioned within the tube such that the males' movements would create both L and T image motion. However, succ essful negotiation of the tube was also unexpectedly facilitated by pa tterns apparently providing no horizontal transverse component for fly ing males but providing longitudinal flow while centering the moth in the plume through a symmetrical left-right input (4-40%).