One of the most difficult things to account for in the life of the honey-bee is the fact that the temperature of the hive can be varied at the will of its occupants. The system of mechanical ventilation will, of course, explain how the hive is kept cool in the greatest heats of summer, but it does not explain the sudden accessions of heat to which it is liable from time to time. These occur principally when the wax is being generated. Under the bronze armour-plates of her body the worker-bee has six shallow, but broad depressions, beneath which the wax-glands are placed. Perfect rest and a high temperature seem to be necessary for the stimulation of these glands, and the wax-makers consume a large quantity of sweet-food during the process. It is generally stated that bees fill themselves from the stores of mature honey before uniting in the cluster; but it is more probable that the food consumed during wax-making is principally the nectar, almost as gathered from the flowers. This view is confirmed by certain experiments which were undertaken to decide the amount of food assimilated during the production of a given weight of wax. When the bees had access only to honey, it was found that five or six pounds were needed during the time that one pound of wax was produced. But if the bees were fed on a plain syrup of cane-sugar, more wax was generated. The chemical composition of fresh nectar is almost identical with that of sugar from the sugar-cane, but mature honey contains practically no cane-sugar at all. It is very doubtful, therefore, if the economic bee would deplete her hard-won stores of honey for a purpose that could be better accomplished in another and cheaper way. And it should also be borne in mind that the natural time for comb-building coincides with the season when nectar is in greatest plenty. These sudden variations in temperature appear to be brought about by a wholesale increase in the rate of respiration among the bees; and there is nothing that excites the wonder of the student of hive-life more than the breathing-apparatus of the bee, as seen under the microscope. Practically her whole physical system is directly supplied with air, drawn in through her many spiracles. As far as scientists have been able to determine, there is not a fibre or nerve in her entire body that is not reached by the minute ramifications of the air-ducts, in direct communication with the great main breathing-vessels in the bee’s abdomen. Respiration appears to be largely voluntary with the honey-bee. She breathes only when the necessity for it arises, and will sometimes arrest the action entirely for three or four minutes together. But when the wax-making is going forward, or swarming-time is near at hand, the quick, vibratory movement of respiration is visible everywhere in the throng of bees, and the temperature of the hive climbs up often to a dozen degrees above its normal point.