Chemical characterization of cuticular extracts of Sitobion avenae (Hemiptera: Aphididae)

Data on the chemical composition of the aphid epicuticle are scarce and often incongruent depending on the methodological parameters of the extraction and chemical analysis. This study aims to provide a chemical characterization of the epicuticular lipids of the English grain aphid, Sitobion avenae (F.) (Hemiptera: Aphididae). First, our results showed that the adsorption chromatography on a silica gel column is suitable to separate the hydrocarbons from more polar constituents found in the extract (e.g., wax esters, alcohols, and aldehydes). Then, we showed that other compounds not detected in previous analysis are likely to be constituents of the extract. Through a transesterification reaction, we demonstrated that the extracts produced numerous fatty acid methyl esters that can come either from long chain wax esters or fatty acid parts of cuticular acylglycerols. The possible semiochemical value of the wax esters and other long chain compounds is discussed. This study opens new insight on the identification of host recognition chemical cues by the parasitoids.