Role of female-produced sex pheromone in behavioral reproductive isolation betweenTrichoplusia ni (Hübner) andPseudoplusia includens (Walker) (Lepidoptera: Noctuidae,plusiinae)

In laboratory flight tunnel bioassays, response rates of male cabbage looper,Trichoplusia ni (Hübner), to female soybean looper,Pseudoplusia includens (Walker), were similar to response rates of maleT. ni to conspecific females for plume tracking and source contact. Male soybean loopers, however, exhibited a greatly reduced response to female cabbage loopers compared to conspecific females. Similar differences were observed in male responses to extracts of female abdominal tips. Studies of flight tunnel responses of male soybean loopers to the different chemicals known to be components of the female cabbage looper sex pheromone indicated that the reduction in response was due to inhibitory effects of (Z)-5-dodecen-1-ol acetate and (Z)-9-tetradecen-1-ol acetate, when added singly to (Z)-7-dodecen-1-ol acetate (major component of both species) at release rates and at ratios close to those observed in female cabbage loopers.