PHEROMONE CHIRALITY OF ASIAN PALM WEEVILS, RHYNCHOPHORUS-FERRUGINEUS (OLIV) AND RHYNCHOPHORUS-VULNERATUS (PANZ) (COLEOPTERA, CURCULIONIDAE)

Production of 4-methyl-5-nonanol, and 4-methyl-5-nonanone by two sympa tric Asian palm weevils, Rhynchophorus ferrugineus (Oliv.) and R. vuln eratus (Pant.) suggested that enantiospecificity of either compound co uld impart species specificity of pheromone communication. Weevil-prod uced, racemic 4-methyl-5-nonanol and 4-methyl-5-nonanone and their ste reoselectively synthesized optical isomers were subjected to gas chrom atographic-electroantennographic detection (GC-EAD) and GC-mass spectr ometry (MS) on a chiral Cyclodex-B column. Only the S,S stereoisomer o f 4-methyl-5-nonanol was EAD active and was produced by both R. ferrug ineus and R. vulneratus. Production and EAD activity of (S)-4-methyl-5 -nonanone exceeded that of its antipode in both weevils. In field expe riments in Java, (4S, 5S)-4-methyl-5-nonanol and the stereoisomeric mi xture were equally attractive. The 4R,5R stereoisomer was inactive. Th e corresponding ketone enantiomers neither enhanced nor reduced attrac tion to (4S,5S)-4-methyl-5-nonanol. Lack of apparent differences betwe en R. ferrugineus and R. vulneratus pheromones suggests that synonomy of both weevils should be considered unless other pre- or postzygotic reproductive isolating mechanisms are disclosed in future studies.