The sex pheromone of bertha armyworm, Mamestra conjigurata (Walker), was reported to be ( a -1 1-hexadecenyl acetate (Z11-16:Ac) and an unidentified tetradecenyl acetate. Electroantennogram responses of male antennae to synthetic isomeric tetradecenyl acetates and attractancy tests under field conditions showed that the highest number of males were captured with a blend of Z9-14:Ac : Z11-16:Ac in a ratio of 1:19 (Underhill et al. 1977). This blend has been useful for monitoring the relative abundances of bertha armyworm; however, in 162 monitor traps in southern Alberta from 1979 to 1982, the catches consisted of 18.4% Agroperina cogitata (Sm) .Recent advances in sex pheromone analyses, particularly the use of high resolution capillary gas chromatography (GC) with simultaneous flame ionization and electroantennographic detectors (GC-FID-EAD) or coupled directly to a mass spectrometer (GC-MS), have greatly facilitated the identification of minor pheromone components (Struble and Am, in press). Extracts from calling female moths were examined by these methods to confirm the presence of Z9-14:Ac and Z11-16:Ac, and to detect any other minor components that might be present. These components were then tested for their effects on the attraction of bertha armyworm males and common nontarget species.GC-FID-EAD and GC-MS conditions were as previously described (Struble 1983) except that glass capillary columns for GC-FID-EAD were 28 m Carbowax 20M TPA and Silar 10C, and a 55 m Carbowax 20M TPA column was used for GC-MS. Excised abdomen tips from 365 calling females were extracted with n-hexane, filtered, concentrated (N,) and analyzed without further clean-up.GC-MS analysis of the extract yielded complete EI and CI (isobutane) mass spectra of compounds having retention indices equivalent to 12:Ac, Z9-14:Ac, 16:Ac, Z9-16:Ac and Z11-16:Ac. Two other compounds, Z7-12:Ac and 14:Ac, were detected, but their spectra were incomplete due to a lack of sensitivity of the GC-MS.Male bertha armyworm antennae gave EAD responses only to Z9-14:Ac and Z11-16:Ac in the female extract. Antennae from males of other species, which had known specific EAD responses (Struble and Am, in press), were used as detector antennae to confirm the isomeric assignments of these two components and for the detection of 27-12:Ac, Z9-14:OH, 27-16:Ac, Z9-16:Ac and Z11-16:OH in the female extract (Table I). These isomeric assignments were based upon GC-FID-EAD retention times and cochromatography with authentic standards on both liquid phases. The estimated relative