The sex pheromone components of the two sibling species of the dingy cutworm that occur on the prairies of western Canada were identified in abdomen-tip extracts from calling female moths. Three monounsaturated acetates, (Z)-7-dodecenyl acetate, (Z)-9-tetradecenyl acetate, and (Z)-11-hexadecenyl acetate, are common to both species in ratios of 100∶13∶3 for species A and 0.3∶0.5∶100 for species B. The most effective synthetic blends for the attraction of male moths in the field consisted of these three components in ratios of 10∶1∶0 at 8.8Μg/lure for species A and 1∶1∶2000 at 500Μg/lure for species B. The addition of Z5-12∶Ac to either blend reduced the catches and the addition of Z7-12∶OH orZ11-16∶OH to the three-component blend reduced the catches of species B males. The species are morphologically indistinguishable, but the identity of the males attracted to the synthetic blends could be confirmed by their antennal responses to a test blend of the three components using a GC-EAD system. Both synthetic attractant blends are competitive with females and will be useful for studying the distribution, biology, and relative abundances of the two species.