Comparison of manoeuvres used by walking versus flying Grapholita molesta males during pheromone-mediated upwind movement

While walking upwind to a pheromone source, male oriental fruit moths, Grapholita molesta (Busck) exhibit none of the temporally regular course reversals (counterturns) and resultant zigzag tracks which characterise the tracks of males flying upwind to pheromone. Rather, males walk in a nearly straight line, steering directly upwind, in contrast to flying males, which steer a course alternating back and forth about 15-20° to either side of the windline. These results support the idea that counterturning in males flying to pheromone sources is a mechanism which enhances their visual perception of wind-induced drift. Counterturning would be unnecessary in walking males, which can perceive wind velocity and direction via mechanoreceptors.