SEX PHEROMONE OFDENDROCTONUS PSEUDOTSUGAE(COLEOPTERA: SCOLYTIDAE): PRODUCTION, BIO-ASSAY, AND PARTIAL ISOLATION

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Abstract
Attractive frass was produced by femaleD.pseudotsugaewithin 2 hours after boring into fresh Douglas-fir logs and peak attraction was reached in 8 hours. Production declined after 2 weeks but increased again if the females were allowed to attack new logs. Frass was collected, stored at −40°C, and extracted in benzene. The extract was distilled and chromatographed on a silica gel column. An olfactometer was developed in which beetles walking toward a light, passed into a narrow air stream. If the air stream contained attractive substances, beetles oriented upwind. Males showed a weak positive response to female frass extract and distillate over a wide range of low stimulus intensities and an abrupt increase at higher intensities. Over 20% of the test beetles responded to concentrations of 5.1 × 10−4and 2.3 × 10−3g-equiv of extract and distillate respectively, while stimulus intensities 100 times greater evoked responses over 80%. The silica gel fraction that eluted in the volume between 350 and 400 ml contained a highly attractive component.