Ice queens: bumble bee social organization shaped by adaptations to cold climates

Bumble bees are an economically and ecologically important group of social insects distributed primarily in boreal and temperate zones. Their social organization is distinct from that of other obligately eusocial taxa, likely because of their climatic adaptations. Queens differ from workers in physiological traits related to cold tolerance, such as size and lipid reserves. They directly manipulate the development of their offspring, reducing its size and developmental time. Manipulation of brood development and variance in body size among adults are important organizing features of bumblebee sociality. Investigation of these traits and of their diversity across species offers an insight into proximate mechanisms underlying evolutionary changes. Here, I review the recent body of work on bumble bee social organization, as well as open questions and directions for future study.