Fig. 2. Response frequencies to varying intensity of sound stimulation in pure air or during attraction to four different pheromone stimuli. The response frequency depended significantly on the sound intensity for all pheromone and none pheromone stimuli (Spearman rank correlation: P<0.01, r=0.886 for 1 component (comp.) 20 ng; P<0.0001, r>0.950 for all other odours). Coloured bars illustrate mean percentages of male moths responding by cessation of walking to sound stimulation (20<N<25 for all treatments). Values represent data means + S.E.M.