Visual cues collimate the trajectories of almond moth Cadra cautella males flying in wind and still air within a wind-formed plume of pheromone

摘要

Male Cadra cautella (Walker) moths are videotaped in three dimensions in a 3-m long wind tunnel as they fly within a 65-cm wide plume of pheromone. Moths are presented two floor patterns, either aligned, a 25-cm wide trail of solid red circles along the tunnel's midline, or offset, in which the trail veers 25 cm to the left at the tunnel's midpoint. These visual patterns are presented either in a continuous airflow or airflow that is stopped before moths reach the tunnel's halfway point. Moths fly relatively straight paths over the aligned pattern in still air after the wind is stopped. With the offset pattern in wind and when the wind is stopped, moths swerve towards the offset pattern before again progressing along the plume. Prominent visual cues appear to collimate (i.e. align with a directional cue) the moth's course as long as the moth remains in contact with pheromone. In wind, these moths appear to favour trajectories that enhance visual feedback, even if the path taken is not directly upwind. During wind lulls, this manoeuvre may enable moths to continue progress towards calling females along a visually set course. The centring of trajectory over prominent visual cues suggests that these moths favour a route that enhances visual feedback.