SummaryThe histology and histochemistry of the fat-body of adult bumble bees are described, with particular reference to queens. Both neutral fat and glycogen, but not protein, are stored in the trophocytes. Protein granules and uric acid concretions occur in newly emerged bees, but are not normally present in older individuals. The quantities of fat and glycogen stored in the trophocytes of workers and males are generally small, but in young queens considerable reserves are accumulated. Most of this fat and glycogen is utilized during hibernation.