SEX-PHEROMONE OF THE WESTERN HEMLOCK LOOPER, LAMBDINA-FISCELLARIA-LUGUBROSA (HULST) (LEPIDOPTERA, GEOMETRIDAE)

The sex pheromone of the western hemlock looper (WHL), Lambdina fiscel laria lugubrosa (Hulst), comprises three methylated hydrocarbons: 5,11 -dimethylheptadecane (5,11), 2,5-dimethytheptadecane (2,5), and 7-meth ylheptadecane (7). Compounds extracted from female pheromone glands we re identified by coupled gas chromatographic-electroantennographic (GC -EAD) analysis and coupled GC-mass spectroscopy in selected ion monito ring mode. In trapping experiments, (5,11) alone attracted male moths, but addition of either (7) or (2,5) significantly enhanced attraction . (5,11) combined with both (7) and (2,5) was significantly most attra ctive. (5,11) and (2,5) are also sex pheromone components of the easte rn hemlock looper (EHL), Lambdina fiscellaria fiscellaria (Guen.). Alt hough (7) is produced by the EHL, it is a pheromone component only in the WHL. It constitutes the first behaviorally active monomethyl-branc hed hydrocarbon to be found in a geometrid and is a novel lepidopteran sex pheromone component. The different 2- versus 3-component sex pher omone supports taxonomic division of EHL and WHL.