Zusammenfassung
The fifth abdominal segment of female Eriocrania semipurpurella (Stephens) and E. sangii (Wood) contains a pair of exocrine glands. Hexane extracts of this segment were prepared from both species and analyzed by gas chromatography with simultaneous flame ionization and electroantennographic detection (EAD). For both species, the EAD active peaks were identified as nonan-2-one, (Z)-6-nonen-2-one, and (Z)-6-nonen-2-ol by means of mass spectrometry and comparison of retention indices with those of synthetic standards. Enantiomeric separation of chiral alcohols from the female extracts was achieved by gas chromatographic analysis on a cyclodextrin column. In E. semipurpurella, a mixture of (2S,6Z)-nonen-2-ol and (2R,6Z)-nonen-2-ol (2:1) was found, whereas in E. sangii (2S,6Z)-nonen-2-ol was the predominant enantiomer and only traces of the R enantiomer were indicated by the antennal response. In held tests, a blend of the three compounds was not attractive to conspecific males. A subtractive assay showed that the alcohol in various enantiomeric mixtures was the only attractive compound, whereas addition of (Z)-6-nonen-2-one to the alcohol completely inhibited the attraction of both species. A trapping experiment including a wide range of ratios between the R and S enantiomers showed that baits containing 95-100% of the S enantiomer were attractive to male E. sangii, whereas males of E. semipurpurella were attracted to all tested ratios of the enantiomers. However, the response profiles of male E. semipurpurella differed between populations from southern Sweden, south Finland, and the Kola Peninsula in Russia. In south Sweden males were maximally attracted to a racemic mixture of the alcohols. At the Kola Peninsula E. semipurpurella was attracted to baits containing 95-100% of the R enantiomer. In south Finland all tested ratios between 0 and 100% R enantiomer trapped E. semipurpurella, but the trap catches appeared to be bimodally distributed with peaks around 15 and 70% R enantiomer. The trapping results suggest the existence of pheromone races or sibling species among the specimens identified as E. semipurpurella.
