Role of chirality in olfactory-directed behavior: aggregation of pine engraver beetles in the genus Ips (Coleoptera: Scolytidae)

There has been a renaissance of interest in the significance of enantiomeric composition in biological systems. Three chiral monoterpene alcohol aggregation pheromone components (ipsenol, ipsdienol, and cis-verbenol) commonly isolated from engraver beetles (Ips spp.) provide a paradigm for this theme as it relates to olfactory-guided insect behavior. The literature pertaining to this system is reviewed and the effects of the enantiomeric composition of these semiochemicals on the Ips spp. community is explored on two trophic levels. Hypotheses generated from the well-studied aggregation pheromone production and response patterns for I. paraconfusus Lanier and I. pini (Say) are generalized to the North American species in the genus. Despite the progress with I. paraconfusus and I. pini, substantial deficiencies exist in our understanding of the role of enantiomeric composition in pheromonal/allomonal effects in different subgeneric groups, in the regulation and mechanisms of stereoselective biosynthesis of the monoterpene alcohols, and in the benefits derived by individual insects that produce relatively large proportions of inactive or interruptive enantiomers with attractive enantiomers