Volatiles from fresh bark of black cottonwood, Populus trichocarpa: trembli
ng aspen, P. tremuloides; paper birch, Betula papyrifera; bigleaf maple, Ac
er macrophyllum; red alder, Alnus rubra; and Sitka alder, Alnus viridis, we
re collected on Porapak Q and subjected to coupled gas chromatographic-elec
troantennographic detection analyses by utilizing the antennae of several s
colytid beetles (Dendroctonus pseudotsugae, D. rufipennis, D. ponderosae, I
ps pini, and Dryocoetes confusus). Among the antennally active volatiles id
entified by coupled gas chromatographic-mass spectroscopic analysis were fr
ontalin, 1,5-dimethyl-6, 8-dioxabicyclo[3.2.1]octane, in the two Alnus spec
ies and conophthorin, (E)-7-methyl-1,6-dioxaspiro[4.5]decane, in the other
four species. Field trapping experiments demonstrated that conophthorin had
a significant disruptant effect on the response to a pheromone-host kairom
one blend by both Dendroctonus psendoaugae and D. ponderosae. Our results,
and the recent identification of other scolytid pheromones in various tree
species, pose major questions regarding the evolution and ecological roles
of these semiochemicals, including the possibility of Batesian mimicry by t
he beetles. They also suggest a need for comparative studies on the biosynt
hetic pathways for these compounds.