In a well-insulated cellar it should not be necessary to ventilate at night at the approach of spring to cool the air inside, for the bees will not get so warm from their own activity as will bees in a cellar that is or has been too cold. The greatest problem in most cellars is to maintain the right temperature during the spring just before the bees are to be removed. The trouble is that in most cellars--those which are too cold in winter--the bees generate heat constantly during the winter and as a result have an accumulation of feces in the intestines, resulting in a condition known as dysentery. For this reason they become excited easily, and beekeepers have thought it necessary to ventilate the cellar at night freely in order to remedy this trouble. The proper method, of course, is to prevent it by keeping the temperature higher during the winter, but if the temperature has fallen too low during the winter ventilation at night seems to help somewhat. It is safe, however, to say that a cellar in which this happens is not satisfactory as a place to keep bees during the winter, and steps should be taken to insulate it more completely before bees are put into it again. If the bees are wintering on stores that are not of the best quality the tendency to accumulate feces will be far greater, even with the right temperatures inside the hives, and if there is dysentery it may be relieved somewhat by ventilation, although this is simply reducing a symptom and is not removing the cause of the trouble.
Since bees in a good cellar require little ventilation, practically no attention need be paid to this subject if the cellar has been built in the way advised. If the temperature of the cellar tends to fall too low, it is advisable to reduce the entrances of the hives, for with a greater difference between the temperatures within and outside the hive the tendency for interchange of air will be correspondingly greater. In any cellar fit for the wintering of bees it will be neither necessary nor desirable to ventilate the hives at the top, as sometimes has been recommended.
The ventilation of the hive within the cellar is not so much for the elimination of foul air as for the escape of moisture, and therefore the amount of ventilation needed for the hive depends upon the humidity of the air within the cellar. If the temperature of the cellar is kept high enough there will be no condensation of moisture within the hive, and if water is ever observed on the covers of the hives it is conclusive proof that the cellar is too cold for the bees. In a cellar so cold that condensed moisture shows on the bottoms of the hives stops should be taken at once to raise the temperature.