Sites of production and occurrence of volatiles in Douglas-fir beetle,Dendroctonus pseudotsugae hopkins.

Volatiles were found to be distributed throughout adult Douglasfir beetles,Dendroctonus pseudotsugae Hopkins, suggesting that the hindgut may not be the sole site of production. The volatile content of individual beetles increased dramatically with feeding; qualitative changes reflected the different bark habitats of newly emerged and established beetles. All detected volatiles were also found in beetle frass. Myrcene was the predominant monoterpene of emergent beetles and α-pinene of fed beetles. Linalool and bornyl acetate occurred in significant amounts after feeding, and diacetone alcohol and sulcatol were also detected for the first time. The presence of sulcatol explains the reported cross-attraction withGnathotrichus spp.cis-Verbenol was also found to occur in addition totrans-verbenol. The volatile content of male beetles was similar to that of females but amounts of individual compounds were less. Acetic acid was found in both emerged and fed beetles and in lesser amounts in frass, suggesting that microbial metabolism could be a potential source of volatile production.