The two components of the aggregation pheromone of the lesser grain borer, Rhyzopertha dominica (F.), are (S)-(+)-1-methylbutyl (E)-2-methyl-2-pentenoate, (DL-1), and (S)-(+)-1-methylbutyl (E)-2,4-dimethyl-2-pentenoate (DL-2). These were evaluated for attractancy to wild populations of lesser grain borers near storage bins containing infested rice. The components and various mixtures were equally attractive, but attractancy increased with dosage. Trap catches of lesser grain borers around the bins were inversely proportional to the height of the traps. When the two components, pure and in various mixtures, were exposed to natural summer conditions, the longevity of DL-2 was approximately twice that of DL-1.