The cells built naturally are not all of the same size, those used in rearing worker bees being about one-fifth of an inch across, and those used in rearing drones and in storing honey about one-fourth of an inch across (fig. 11). The upper cells in natural combs are more irregular, and generally curve upward at the outer end. They are used chiefly for the storage of honey. Under manipulation the size of the cells is controlled by the bee keeper by the use of comb foundation--sheets of pure beeswax on which are impressed the bases of cells and on which the bees build the side walls. [Illustration: Fig. 10.--The honey bee: _a_, Worker; _b_, queen; _c_, drone. Twice natural size.] In the North, when the activity of the spring begins, the normal colony consists of the queen and some thousands of workers. As the outside temperature raises, the queen begins to lay eggs (fig. 12, _a_) in the worker cells. These in time develop into white larvæ (fig. 12, _b_, _c_), which grow to fill the cells. They are then capped over and transform first into pupæ (fig. 12, _d_) and then into adult worker bees. As the weather grows warmer, and the colony increases in size by the emergence of the young bees, the quantity of brood is increased. The workers continue to bring in pollen, nectar to be made into honey, and water for brood rearing. When the hive is nearly filled with bees and stores, or when a heavy honey flow is on, the queen begins to lay eggs in the larger cells, and these develop into drones or males. Continued increase of the colony would result in the formation of enormous, colonies, and unless some division takes place no increase in the number of colonies will result. Finally, however, the workers begin to build queen cells (fig. 13). These are larger than any other cells In the hive and hang on the comb vertically. In size and shape they may be likened to a peanut, and are also rough on the outside. In preparing for swarming the queen sometimes lays eggs in partly constructed queen cells, but when a colony becomes queenless the cells are built around female larvæ. The larvæ in these cells receive special food, and when they have grown to full size they, too, are sealed up, and the colony is then ready for swarming. [Illustration: Fig. 11.--Comb architecture: _a_, Vertical section at top of comb; _b_, vertical section showing transition from worker to drone cells; _c_, horizontal section at side of comb showing end bar of frame; _d_, horizontal section of worker brood cells; e, diagram showing transition cells. Natural size.] The issuing of the first swarm from a colony consists of the departure of the original queen with part of the workers. They leave behind the honev stores, except such as they can carry in their honey stomachs, the brood, some workers, drones, several queen cells, from which will later emerge young queens, but no adult queen. By this interesting process the original colony is divided into two.