Interspecific Inhibition of the Response of the Bark Beetles, Dendroctonus Brevicomis and Lps Paraconfusus, 1 to Their Pheromones in the Field

-Ponderosa pine logs infested with Ips paraconfusus males inhibited the attraction of Dendroctonus brevicomis in the field to either attractive logs cut from a ponderosa pine tree under attack by D. brevicomis or to their synthetic pheromones, exo-brevicomin, frontalin, and myrcene. Logs cut from trees under attack by D. brevicomis inhibited the response of L paraconfusus to logs infested with male L paraconfusus. Exo-brevicomin, frontalin, and myrcene did not inhibit their response but verbenone did. Verbenone was found in male D. brevicomis dissected from attractive logs under attack during the same time the response of L paraconfusus was inhibited by these logs. Trans-verbenol and exo-brevicomin were found in female D. brevicomis while verbenone, trans-verbenol, and frontalin were found in male D. brevicomis in relatively large amounts near the beginning of the aggregation phase of host colonization. All of these compounds had decreased at a similar rate 5 days later. This gradual decrease in exobrevicomin and frontalin probably caused the observed reduction in attraction. The ecological significance of these compounds in relation to termination of the aggregation phase of D. brevicomis and reduction of interspecific competition is discussed. Key Words--Dendroctonus brevicomis, lps paraconfusus, Pinus ponderosa, bark beetle, exo-brevicomin, frontalin, myrcene, verbenone, transverbenol, attractants, inhibition, pheromones. ~Coleoptera: Scolytidae. This paper is based in part upon a dissertation submitted by J.A.B. to the University of California, Berkeley, in partial fulfillment of the requirements for the PhD in entomology. These studies were supported in part by the Rockefeller Foundation; U.S. Forest Service; Regional research Project W-I 10, S.E.A./U.S.DA.; and the National Science Foundation and Environmental Protection Agency through a grant (NSF GB-34719/BMS 75-04223) to the University of California.