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Thirty-five populations ofIps pini (Say) and one population each ofIps avulsus (Eichhoff) andIps bonanseai (Hopkins) were analyzed for the enantiomeric composition of ipsdienol (2-methyl-6-methylene-2,7-octadien-4-ol). Populations ofI. pini occur as at least two distinct regional pheromone variants: New York type [32%-(-) to 56%-(-)-ipsdienol] and California type [94%-(-) to 98%-(-)-ipsdienol]. A third phenotype may occur in southeastern British Columbia, Idaho, and Montana [91%-(-) to 95%-(-)], possibly indicating a zone of hybridization. Populations of the New York type occur in southwestern British Columbia, Alberta, Saskatchewan, Minnesota, and Wisconsin suggesting a continuum through the Canadian provinces and Lake States. The presence of the New York type in western Canada is likely linked to the Quaternary history of the transcontinentally distributed host,Pinus banksiana Lamb. MaleI. avulsus [∼25%-(-)] and maleI. bonanseai [-29%-(-)] both produce ipsdienol, but not ipsenol. Production of ipsdienol by maleI. pini was evaluated in six differentPinus spp. hosts. Following transfer of maleI. pini to hosts other than the host of origin, the percentage of the (-)-enantiomer of ipsdienol declined when compared to production in the host of origin.

The attraction of the red turpentine beetle,Dendroctonus valens, to the resin volatiles of its host,Pinus ponderosa, is elicited by three chiral monoterpenes. In field assays response was greatest to (S)-(-)-β-pinene; 92% (S)-(-)-α-pinene found inP ponderosa resin was not attractive. However, 75% (R)-(+)-α-pinene, which occurs inPinus lambertiana, a sympatric host ofD. valens, was attractive. (S)-(-)-α-Pinene interrupted response to (R)-(+)-α-pinene. (S)-(+)-3-Carene from both hosts was attractive at the (R)-(+)-α-pinene level. Three sympatric coniferous nonhosts each have the same attractive monoterpenes but produce less resin. These studies demonstrate the importance of chirality of host compounds in the host finding behavior of this bark beetle.

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