(4) _The bees must be kept dry and warm._--A substantial hive with a tight roof will keep rain and snow from the cluster; but the bees must have air even during the severest weather and also when in their most quiescent state; hence the question of ventilation has to be considered. It has occasioned more discussion and experimentation than any other point concerned in the wintering of bees. The amount of ventilation both indoors and outside, whether upward ventilation or lower ventilation, or both, and whether through the wooden walls of the hive alone, have given rise to thousands of experiments based on all sorts of theories, and innumerable losses have resulted. The matter is really more complicated than would seem at first thought. The warm air about the bodies of the bees (the winter temperature of the cluster being about 72° F.) coming in contact with the cold surfaces of combs of honey in ordinary hives, or with the inner Avails of such hives, condensation and deposition of moisture occurs. During severe weather this accumulates in the shape of hoarfrost, which, melting with a rise of temperature, trickles down over the combs, the walls of the hive, and the bees themselves, and, entering the honey cells through the somewhat porous capping, sours the honey with which it mixes. The soured food, dampness, and chilling of the bees combine to bring on diarrhea, which is sure to weaken and decimate the colony if it does not exterminate it. To avoid these troubles the surplus moisture of the hive must be carried away by free ventilation, which at the same time supplies pure air, but which does not create drafts in the hive nor permit such an escape of heat as will chill the cluster through. Straw hives (fig. 72) do this well; also the forms shown in figs. 73 and 74 if well packed over the combs and ventilated above the packing. [Illustration: Fig. 74.--Double-walled hive adapted to outdoor wintering as well as summer use below 40° north latitude in the United States. Thickness of each wall, ⅜ inch; space between walls, 2 inches, packed with dry chaff or ground cork. (Original.)] (5) _There should be no manipulation out of season._--Breaking up the cluster and exposing the individual bees and their combs to a low temperature, as well as causing them to gorge themselves with honey when an opportunity for a cleansing flight may not occur soon, are also causes which bring on diarrheal difficulties. Feeding to complete the winter stores, when necessary, should be done soon after the last honey flow, so that the bees will settle down for the winter on the approach of cool autumn days. After this they are better off if left undisturbed until the final work of preparing them for winter is done, which, if the hive is well arranged, will be no material disturbance to the bees. It is always preferable not to be obliged to touch the brood combs or disturb the cluster when the weather is too cold for the bees to fly freely.