Cuticular lipid constituents of cabbage seedpod weevils and host plant oviposition sites as potential pheromones

The cuticular lipids of cabbage seedpod weevils ( Ceutorrhynchus assimilis Payk.) and those at their oviposition site, i.e., the seed pods of the host plant ( Brassica napus L.), were analyzed by chromatographic techniques in conjunction with mass spectrometry (MS). Long chain hydrocarbons were most abundant in both lipids; however, the seed pods of B. napus contained n ‐alkanes only, whereas C. assimilis showed a predominance of dimethylalkanes over internally branched methylalkanes as well as iso‐ and n ‐alkanes. The amounts of ketones, secondary alcohols and aldehydes, the usual plant components that are unique in insects, occurred in cuticular lipids of both organisms in approximately the same ratio. The composition of n ‐alkanes, n ‐ketones, secondary n ‐alcohols, iso‐ and anteisoaldehydes and esterified primary anteiso‐alcohols of wax esters was similar between C. assimilis and B. napus . In both sources, qualitative but not quantitative similarities were observed in the composition of n ‐aldehydes and esterified primary n ‐ and iso‐alcohols, respectively. The esterified fatty acids of wax esters from B. napus were composed of roughly equal proportions of saturated branched and unbranched components. The esterified fatty acids of wax esters and steryl esters from C. assimilis consisted of major proportions of saturated as well as unsaturated n ‐compounds, whereas iso‐ and anteiso structures were present in minor proportions only. Free fatty acids and traces of ethyl esters of fatty acids found in C. assimilis were mainly composed of unsaturated n ‐compounds.