Scent marking, scent origin, and species specificity in male premating behavior of two Scandinavian bumblebees

The marking behavior and the scent-marking compounds in males of two Scandinavian bumblebee species Bombus pratorum and Bombus lapidarius were studied. There are characteristic differences in the behavior and in the chemistry of the two species. Males of B. pratorum scent marked small areas of the edges of birch leaves in a quick and unpredictable manner, depositing farnesol, geranylgeranyl acetate, farnesyl acetate, (Z)-11-octadecanol, hexadecanol, and a pentacosadiene. In B. lapidarius, scent marking on birch leaves was much slower and the entire edge of the leaf was marked with (Z)-9-hexadecenol and hexadecanol. These compounds were also detected in the cephalic portion of the labial gland in males. Thus, males of B. lapidarius produce a blend of fatty acid derivatives while B. pratorum males, in addition to fatty acid derivatives, also produce sesqui- and diterpenes. The total amount of scent compounds per milligram of labial glands was 0.2 mu g in B. pratorum and 40 mu g in B. lapidarius. Farnesol and farnesyl acetate were detected via headspace collection in the air around leaves marked by B. pratorum and (Z)-9-hexadecenol was detected around leaves marked by B. lapidarius.