Stereospecific antennal response by red turpentine beetle,Dendroctonus valens to chiral monoterpenes from ponderosa pine resin.

The antennal response ofDendroctonus valens to host monoterpenes from the resin of ponderosa pine was studied using the electroantennogram (EAG) technique. Male and female beetles were given a single dose of each of 11 different monoterpenes. Response amplitude to the different compounds did not vary between sexes and was generally well correlated with results from field attraction studies. Response to (S)-(-)-β-pinene was greatest. The relative amplitude of the responses to the (R)-(+) and (S)-(-) enantiomers of a-pinene, however, were reversed from their relative attractiveness in the field. A dose-response study was conducted for the (R)-(+) and (S) -(-) enantiomers of a-pinene, plus a reciprocal differential saturation test with successive doses of first one enantiomer ofα-pinene and then the other. Comparison of EAG traces suggests different receptors for the two stereoisomers ofα-pinene. Differential saturation curves suggest that while one set of receptors may respond to both enantiomers, some receptors respond only to the (S)-(-) enantiomer.