Electroantennograms by mountain pine beetles,Dendroctonus ponderosae Hopkins, exposed to selected chiral semiochemicals.

Electroantennograms (EAGs) were recorded fromD. ponderosae to the enantiomers of the terpenoid bark-beetle pheromonestrans-verbenol,cis-verbenol, verbenone, and the bicyclic ketals frontalin,exo-brevicomin, andendo-brevicomin. Male and female responses to enantiomers of the terpenoids differed significantly only at the two highest concentrations. No sex differences were seen in response to the bicyclic ketals. Significantly different responses to the enantiomers of all the chemicals, except frontalin, were noted over at least part of the dosage-response ranges tested. The negative antipode for all of the terpenoids elicited higher responses, while for the bicyclic ketals, the positive antipode effected the largest responses except for the two highest concentrations ofexo-brevicomin.