Five principal semiochemicals were field tested in multiple funnel traps for behavioral activity against Dendroctonusponderosae infesting lodgepole pine, Pinuscontorta var. latifolia Engelmann, in British Columbia. The basic experimental design was to test each compound by adding it in varying concentration or enantiomeric composition to a blend of other semiochemicals. (−)-trans-Verbenol was attractive to both sexes. (±)-exo-Brevicomin and (±)-frontalin (in one of two experiments) were attractive with other semiochemicals to females at a release rate of 0.05 mg/24 h. At higher release rates (±)-exo-brevicomin was inhibitory to males, and frontalin was inhibitory to both sexes. Thus both serve as multifunctional pheromones. For neither exo-brevicomin nor frontalin were the separate enantiomers attractive at the low release rate, suggesting that they had an additive effect. However, at the high release rate both enantiomers mimicked the inhibitory effect of the racemates. Verbenone acted as an antiaggregation pheromone for both sexes. Increasing the release rate of myrcene from 18 to 150 mg/24 h to approximate the release rate from a newly attacked tree had the effect of doubling the catch of responding beetles. A conceptual model is proposed for the sequential interaction of these semiochemicals in the mass attack of a tree. Pioneer females release trans-verbenol, which acts in combination with myrcene from the host tree to attract mainly males. The responding males release exo-brevicomin and later frontalin, which in combination with trans-verbenol and myrcene attract mainly females. Meanwhile autoxidation of α-pinene in the host resin results first in the production of predominately trans-verbenol, which supplements that produced by the beetles. Later, autoxidation of α-pinene and microbial conversion of cis- and trans-verbenol result in the production of the antiaggregation pheromone verbenone. This compound, in combination with large amounts of exo-brevicomin and frontalin as the tree becomes fully occupied, results in the close-range redirection of responding beetles toward nearby trees.

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Stress and attraction chirps, which were similar in acoustic parameters, and multi‐interrupted rivalry chirps were recorded from male D. valens. From females were recorded stress chirps, longer and irregularly‐pulsed agreement stridulations, and “greeting” chirps produced at first physical contact with a male entering the attractive female gallery. This is the first direct evidence of male‐female acoustic interplay in Scolytidae. Zusammenfassung Geräuscherzeugung bei Scolytiden: Die akustischen Signale der Männchen und Weibchen bei Dendroctonus valens LeConte Stridulationsignale, die akustisch ähnlich sind, wurden als Ausdruck von Stress und Anlockung durch Männchen produziert. Während einer Rivalitäts‐Situation dagegen wurde eine vielfach unterbrochene Stridulation erzeugt. Die Weibchen produzierten Stress‐Signale, längere irreguläre „Zustimmungs”‐Signale, und ‐ nach Eindringen der Männchen in die Brutgänge ‐ „Begrüßungs”‐Signale. Diese „Begrüßungs”‐Stridulation wird als der erste Beweis der akustischen Kommunikation zwischen Männchen und Weibchen bei Scolytiden betrachtet.

Volatiles produced by mountain pine beetles (MPB), Dendroctonus ponderosae, were identified by GC/MS from air passed over emergent males, fed males, and the frass of virgin females reared from lodgepole, ponderosa, white, and sugar pine. exo‐ and endo‐Brevicomin were released by males from all four hosts. Unfed males from lodgepole pine also released diacetone alcohol; unfed males from white pine released frontalin. The frass of females from all four hosts released trans‐verbenol, linalool, borneol, verbenone, myrtenol, and piperitone. Other volatiles such as cis‐verbenol, trans‐pinocarveol, terpinen‐4‐ol, alpha‐terpineol, octanone, and 2‐p‐methen‐7‐ol, were detected from frass of MPB reared from certain hosts but not others. Results of cross‐feeding experiments between MPB from white and lodgepole pine indicated that differences in frass volatiles among the populations studied result from the monoterpene composition of the host pine diet rather than from physiological differences among populations. Males reared from and fed in all four hosts released frontalin and various other volatiles. In field bioassays, 3‐caren‐10‐ol changed the sex ratio of MPB trapped to favor males, and pinocarvone reduced the response to 48 % of the attractant control. Linalool, piperitone, trans‐pinocarveol, acetone, and ethanol did not affect trap catches at the evaporation rates tested. exo‐Brevicomin was inhibitive at the highest concentration tested and had no affect on aggregation at lower evaporation rates down to < 1 ppm. (‐)‐trans‐Verbenol and myrcene attracted more male MPB than (+)‐trans‐verbenol and (+)‐alpha‐pinene, respectively; but females were attracted equally. A high concentration of frontalin inhibited aggregation, but a low concentration (100 ng/h) neither inhibited nor enhanced aggregation. Zusammenfassung Labor‐ und Freilandstudien über flüchtige Substanzen durch Dendroctonus ponderosae Hopkins (Coleoptera, Scolytidae) Substanzen, produziert von Bergkiefern‐Borkenkäfern (BBK), Dendroctonus ponderosae, wurden mittels GC/MS identifiziert, und zwar aus der Luft, die sich über den Mächen nach dem Schlüpfen und nach dem Fraß befand sowie auch über dem Fraßabfall jungfräulicher Weibchen, die aus Pinus contorta, P. ponderosa, P. monticola und P. lambertiana gezogen wurden. Exo‐ und Endo‐Brevicomin wurden von Männchen aus allen 4 Wirten abgesondert. Ungefätterte Männchen aus P. contorta sonderten Diaceton‐Alkohol, ungefütterte Männchen aus P. monticola Frontalin ab. Der Fraßabfall von Weibchen aus allen 4 Wirten sonderte folgende Stoffe ab: trans‐Verbenol, Linalool, Borneol, Verbenon, Myrtenol und Piperiton. Andere Substanzen wie z. B. cis‐Verbenol, trans‐Pinocarveol, Terpinen‐4‐ol, alpha‐Terpneol, Octanon und 2‐p‐Menthen‐7‐ol, wurden im Fraßabfall der BBK, die aus einigen Wirten gezogen wurden, festgestellt. Die Ergebnisse von Kreuzfütterungs‐Experimenten zwischen BBK von P. monticola und P. contorta zeigten, daß Unterschiede in den Fraßabfall‐Substanzen bei den untersuchten Populationen eher aus der monoterpenen...