Active space, the area over which a stimulus elicits a behavioural reaction in a receiving individual, is an important yet seldom investigated aspect of insect behaviour. It defines the spatial scale over which insects interact with a stimulus and can influence mating success and population dynamics. From an applied perspective, active space is an important component of the effective range of semiochemical-baited traps used for surveillance of forest and agricultural insects. This study used wingfanning assays, competitive trapping, and portable electroantennography to investigate the active space of spruce budworm, Choristoneura fumiferana Clemens (Lepidoptera: Tortricidae) pheromone-baited traps. Wingfanning assays and portable electroantennography were also used to investigate the active space of and spongy moth, Lymantria dispar dispar L. (Lepidoptera: Erebidae) pheromone-baited traps.