Sensitivity of antennae of male and femaleIps paraconfusus (Coleoptera: Scolytidae) to their natural aggregation pheromone and its enantiomeric components.

Antennae of male and femaleIps paraconfusus were equally and highly sensitive to their male-produced, multicomponent aggregation pheromone. Female and male antennae were highly sensitive to the pheromonal component, (S)-(-)-ipsenol, but essentially insensitive to its antipode, (R)-(+)-ipsenol. Further, female and male antennae were more sensitive to the pheromonal component, (S)-cis-verbenol, than to its antipode, (R)-cis-verbenol. Dramatic sexual dimorphism in chiral sensitivity to the ipsdienol enantiortiers was found, with female antennae being more sensitive to the conspecific pheromonal enantiomer, (S)-(+)-ipsdienol, and male antennae being more sensitive to the antipode, (R)-(-)-ipsdienol. Since (R)-(-)-ipsdienol is the principal pheromone of CaliforniaIps pini and interruptsI. paraconfusus aggregation, male antennae appear to be more sensitive to an interspecific allomone than a conspecific pheromone. Of the conspecific pheromonal enantiomers, both male and female antennae were most sensitive to (S)-(+)-ipsdienol, intermediately sensitive to (S)-(-)-ipsenol, and least sensitive to (S)-cis-verbenol. However, when enantiomeric sensitivities were compared to the estimated concentrations of these components in the natural pheromone, (S)-(~)-ipsenol tended to equal or approach the potency of (S)-(+)-ipsdienol as an antennal stimulant, while antennal responsiveness to (S)-cis-verbenol was dramatically less than for the other two pheromonal components. The behavioral implications of such physiological sensitivities are discussed in regard to perception of multicomponent synergistic pheromones and the relative efficacy of each component as an orientation cue.