Pheromone parsimony is widespread within the longhorned beetles (Coleoptera: Cerambycidae), which share a number of highly conserved volatile pheromone motifs. This parsimony reflects their life histories, ecology, and distribution. We conducted field bioassays testing attraction of cerambycids to 12 volatile pheromone lures at sites in both northern and southern Idaho over a period of three years. Our overall goals were to investigate the role of volatile pheromones in the geographic distribution of cerambycid species, interactions within cerambycid communities in reproductive isolation, and to identify attractive pheromones that can be used to develop lures for monitoring cerambycids. This study focused on the genus Tragosoma (subfamily: Prioninae). Trapping results suggested a regional split between populations of T. harrisii LeConte and T. soror Laplante within Idaho, with the more abundant of the two species at our sites being T. harrisii in northern Idaho and T. soror in southern Idaho. We found the flight periods of T. harrisii and T. soror overlapped, suggesting that flight period is not being used by these two species as a mechanism to prevent inter-specific cross-attraction among their populations in Idaho. Our results increase understanding of the ecology of Tragosoma species, and the role of pheromones and flight period phenology in maintaining reproductive isolation, and will aid in development of lures for monitoring cerambycids.