1Dipartimento di Biologia Animale e Genetica, via Romana 17, 50129, Firenze, Italia.
2Chemical Ecology Group, School of Chemistry and Physics, Keele University, Staffordshire, ST5 5BG, UK.
Much evidence indicates that the cuticular hydrocarbon mixture is the signature which allows for the discrimination between nestmate and alien individuals in social insect colonies. However the importance of the single compounds or of the different classes of hydrocarbons as nestmate recognition cues is unknown. Using a combination of organic synthesis and recognition bioassay we are now beginning to decode the information content of the cuticular hydrocarbon profiles by looking at the role of individual compounds. A series of Z-alkenes and methyl branched alkanes were synthesised and these compounds, together with several linear alkanes, were then tested in recognition bioassays on the social wasp Polistes dominulus. The experiments have shown that the addition of alkanes to the cuticle of an individual has no observable effect upon the recognition response of nestmates. However individuals that have had a Z-alkene or a methyl branched alkane added to their cuticle were treated aggressively by their nestmates. From these we have concluded that in P. dominulus methyl branched alkanes and Z-alkenes encode nestmate recognition cues, while straight chain alkanes encode no recognition information. Moreover, methyl branched alkanes appear to elicit more aggressive responses that Z-alkenes, although no statistical differences resulted from the two sets of experiments.