The two ant species Camponotus ligniperda ,(Latr.) and Camponotus herculeanus (L.) show very small differences in morphology and general biology. The present work demonstrates that the two species are very similar also with respect to the composition of the volatile secretions emanating from Dufour's gland in worker ants. As in other formicine ant species analysed by us earlier, the main components are straight chain, satured hydrocarbons with II, I3, I5 and I7 carbons atoms. Tridecane is the dominating component. Unsatured, straight chain hydrocarbons and branched chain, saturated hydrocarbons are also present. We have also identified aliphatic alcohols, ketones and acetates as components of the secretion from Dufour's gland, as well as a11-trans-farnesyl acetate and one isomer of farnesene in trace amounts. Of these compounds hexadecyl acetate is the dominating one. The analyses have been carried out by combined gas chromatography and mass spectrometry and by capillary gas chromatography. In both techniques we have been using a precolumn for isolating the volatile compounds. The two ant species Camponotus ligniperda ,(Latr.) and Camponotus herculeanus (L.) show very small differences in morphology and general biology. The present work demonstrates that the two species are very similar also with respect to the composition of the volatile secretions emanating from Dufour's gland in worker ants. As in other formicine ant species analysed by us earlier, the main components are straight chain, satured hydrocarbons with II, I3, I5 and I7 carbons atoms. Tridecane is the dominating component. Unsatured, straight chain hydrocarbons and branched chain, saturated hydrocarbons are also present. We have also identified aliphatic alcohols, ketones and acetates as components of the secretion from Dufour's gland, as well as a11-trans-farnesyl acetate and one isomer of farnesene in trace amounts. Of these compounds hexadecyl acetate is the dominating one. The analyses have been carried out by combined gas chromatography and mass spectrometry and by capillary gas chromatography. In both techniques we have been using a precolumn for isolating the volatile compounds.