A simplified protocol for bumble bee species identification by cephalic secretion analysis

Studies of bumble bee male sex pheromones are often based on hexane extraction of cephalic labial gland secretions. Here, we propose an alternative extraction procedure based on whole head extractions. To test this method, we compared cephalic parts of the labial glands (CLG) to whole head extractions using high-sensitivity gas chromatography coupled to mass spectrometry (GC–MS) analysis. Two species were analyzed: Bombus terrestris dalmatinus and Bombus ignitus ignitus. We used correlation coefficients, cluster analysis and the two-group k-means method to test the similarity between the two extractions of the two species. We also used the indicator value (IndVal) method to characterize the indicator compounds of each procedure. Statistical analyses reveal a similar compound extraction using both methods. This simplified sample preparation gives reliable results and is more suitable for broad-scale sampling both by specialists and by amateur collectors. Using this method, we provide the first description of the male pheromonal secretions of B. ignitus ignitus and demonstrate that these secretions are very similar to the pheromonal blend of B. terrestris dalmatinus where 44/51 compounds are shared.