Chemical basis for odour communication in four species of Lasius ants

Abstract

The volatile secretions from gaster, thorax, and head of four formicine worker ants: Lasius niger, Lasius alienus, Lasius flavus, and Lasius carniolicus have been analysed with combined gas chromatography and mass spectrometry. The contents of the abdominal secretions show great similarities in the composition of the hydrocarbons present. They all contain hendecane as a main component, together with other straight chain hydrocarbons with 10 to 19 carbon atoms. In the abdominal secretion of L. niger a series of aliphatic, straight chain acetates (C 10–C 18) were found, and a small amount of all- trans-farnesyl acetate. Aliphatic, straight chain ketones (C 13–C 19) were found in the secretions from L. alienus and L. carniolicus. 4-Hydroxyoctadec-9-enolide was identified in the secretion of L. flavus together with the corresponding free acid, 4-hydroxy-octadec-9-enoic acid and, in minor amounts, the lower homologue with 2 carbon atoms less. Neither the acid nor its lactone seems to have been reported previously in the literature. The results of the analysis of abdominal tips of L. niger, L. alienus, and L. flavus make it highly probable that all abdominal substances identified emanate from Dufour's gland. We did not find any volatile substances from the thorax in the four species studied. The cephalic secretions contained isoprenoids in varying amounts, with the exception of L. niger, from which only small amounts of 1-octanol and 1-nonanol were found. From L. flavus citronellal and a 2,3-dihydrofarnesal were identified and from L. alienus small amounts of at least two sesquiterpenes, probably isomeric dihydrofarnesals. L. carniolicus was found to contain great amounts of isoprenoids, mainly citronellal and, very likely, geranylcitronellal, together with smaller amounts of several other isoprenoids. Functional tests are in progress, and it is clear from preliminary experiments with L. niger that hendecane functions as an alarm pheromone for this ant.