Sex-specific chemical secretions have been widely used as diagnostic characters in chemotaxonomy. The taxonomically confused group of bumblebees has reaped the benefit of this approach through the analyses of cephalic labial gland secretions (CLGS). Most of currently available CLGS descriptions concern species from the West-Palearctic region but few from the New World. Here, the CLGS of four East-Palearctic species Bombus deuteronymus, B. filchnerae, B. humilis, and B. exil (subgenus Thoracobombus) are analysed. Our results show high levels of variability in the major compounds in B. exil. In contrast, we describe a low differentiation in CLGS compounds between B. filchnerae and its phylogenetically closely related taxon B. muscorum. Moreover, the chemical profiles of B. filchnerae and B. muscorum are characterized by low concentrations of the C16 component, which is found in higher concentrations in the other Thoracobombus species. This raises the possibility that courtship behavior as well as environmental constraints could affect the role of the bumblebee males' CLGS.

Faculty of Tropical AgriSciences Department of Sustainable Technologies Czech University of Life Sciences Kamýcká 129 CZ 165 21 Prague Czech Republic

Institute of Organic Chemistry and Biochemistry Academy of Sciences of the Czech Republic Flemingovo nám 2 CZ 166 10 Prague Czech Republic

Research Institute of Biosciences Laboratory of Zoology University of Mons Place du Parc 20 7000 Mons Belgium

Research Institute of Biosciences Laboratory of Zoology University of Mons Place du Parc 20 7000 Mons Belgium Research Unit Animal and Functionalities of Animal Products University of Lorraine INRA 2 Avenue de la Forêt de Haye BP 172 54505 Vandœuvre lès Nancy France

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