The empress' new clothes: Do cuticular hydrocarbon profiles of aging bumblebee queens change in the same way across species?

Chemical signals are an important mode of communication between workers and queens in social species. However, the content of these signals and their links to queen physiology are not well understood in many species, especially those with an annual life cycle in which both queen physiology and the social setting in which she operates differ vastly at different time points. In one such species, the bumblebee, cuticular hydrocarbons seem to play a role in queen-worker communication and this role depends on the queen's life stage. In our current study we analyzed the cuticular hydrocarbon profiles of spring queens and late summer gynes of several wild bumblebee species to assess how they change with the queen’s progression through her life cycle and whether these changes follow the same trajectory in different species. The hydrocarbon profiles differed greatly both between species and between queens of the same species captured in different seasons. One feature common to several species was the decrease in the proportion of acetate esters in spring queens compared to late summer gynes. The chain length profile across species differed also with season in an unexpected way. These findings suggest that conserved mechanisms regulate the composition of CHC profiles and provide the links between queen physiology and chemical signals. However, given the unfortunately small sample size for late summer gynes and the possible differences in phenology among species we should interpret these findings cautiously and acquire more data on the subject.