Laboratory arrestment tests withDendroctonus frontalisZimmerman confirmed that a high concentration of the pheromone verbenone inhibits male response to the known attractants of this beetle. However, a very low concentration of verbenone combined with these attractants elicited significantly more male arrestment than did the attractants alone. Male stridulation also differed according to the concentration of verbenone present in the pheromone mixture. A low concentration evoked the “attractant” chirp characteristic of male response to the female attractant, but a medium concentration of verbenone evoked the male “rivalry” chirp characteristic of male fighting. Since it is known that females produce a small quantity and males a large quantity of verbenone, these different effects are suggested as multiple functions of the pheromone.