Enantiomeric anosmia in scarab beetles

The sex pheromone for Anomala octiescostata has been previously identified as a 4:1 mixture of (R)-buibuilactone and (R)-japonilure. Field experiments showed that although not active per se, the secondary component increased the activity of major component buibuilactone. The enantiomers of these sem iochemicals, i.e., (S)-buibuilactone and (S)-japonilure are neither attract ants nor behavioral antagonists to the pheromone system of A. octiescostata . Chiral GC-EAD experiments demonstrated that, in marked contrast to the Ja panese beetle and Osaka beetle, which can detect a stereoisomer not produce d by their conspecific females, the male antennae of A. octiescostata lack olfactory receptor neurons (ORNs) tuned to (S)-buibuilactone. The same enan tiomeric anosmia (inability to smell a compound) was also observed in Anoma la cuprea male antennae. Both in a Y-olfactometer and field experiments, it was clarified that (S)-buibuilactone was not a behavioral antagonist for A . cuprea. Contrary to male antennae of both A. octiescostata and A. cuprea, which lack ORNs tuned to the nonnatural (S)-buibuilactone, fragrance evalu ation by skilled perfumers revealed that the human nose can discriminate (b oth in intensity and quality) enantiomerically pure samples of (R)- and (S) -buibuilactone and japonilure.