Figure 1. A linalool background alters orientation of male Spodoptera littoralis to pheromone source.

Walking activity and orientation behaviour of male Spodoptera littoralis were measured on a locomotion compensator. Males were submitted to the main pheromone component, Z9E11–14:Ac during 2 min, 1a: a neutral background was maintained for the duration of the test (n = 30). 1b: in addition to pheromone, a linalool background was applied after 1 min (n = 42). Mean upwind speed: average of the distances per second walked by males in direction of the source (solid line) and mean ± SEM (dashed lines). Orientation index: oi = cos (θ) * ρ, where θ is the mean angle of track sample and ρ the length of the mean vector at t_i. Horizontal grey bar = linalool background.