Chemistry of the Cephalic Labial Gland Secretions of Male Bombus morrisoni and B. rufocinctus, Two North American Bumblebee Males with Perching Behavior

The labial gland secretions from males of the North American bumblebees Bombus morrisoni Cresson and B. rufocinctus Cresson were analyzed by gas chromatography/mass spectrometry. In both species, 3,7,11,15-tetramethyl-2,6,10,14-hexadecatetraenyl acetate was found as the major compound of a complex mixture of alkenols, acetates, hydrocarbons, and wax-type esters. In addition to a mixture of saturated and mono-unsaturated straight chain hydrocarbons, the labial gland of both species contained the isoprenoid hydrocarbons (6E, 10E)-3,7,15-trimethyl-3-methylene-hexadeca-1,6,10,14-tetraene β-springene], three isomers of 3,7,11,15-tetramethyl-hexadeca-1,3,6,10,14-pentaene α-springene], and two further unidentified cyclic diterpenes. In B. morrisoni, 3,7,11-trimethyl-2,6,10-dodecatrien-1-ol and 3,7,11,15-tetramethyl-6,10,14-hexadecatrien-1-ol were detected as characteristic alcohols, as well as small amounts of 9-hexadecenol and hexadecanol. Furthermore, a large peak of hexadecyl dodecanoate and minor amounts of 9-hexadecenyl, 9-octadecenyl, and eicosenyl 9-tetradecenoate were found as typical esters in this species. In B. rufocinctus, 9-hexadecenol, hexadecanol, and 9-octadecenol were present in considerable amounts, with their acetates and 9-tetradecenoic, tetradecanoic, hexadecanoic, and 11-octadecenoic acids. The chemical composition of cephalic labial glands in male bumblebees with perching behavior is discussed.