It has been found by the authors that bees do the least amount of work when the temperature of the air immediately surrounding them (inside the hive) stands at 57° F. This is, therefore, the temperature which the beekeeper should bear in mind, rather than to lay too much stress on the temperature of the cellar itself. The place for a thermometer in the bee cellar is inside the entrance of a good colony where it may be read easily by simply pulling it out. A chemical thermometer is best for this purpose, and it should register 52° F. or more inside the hive entrance. In order to have the right temperature within the hive it usually will be best to have the temperature of the cellar at about 50° F. or slightly higher. As will be shown later, however, it is quite possible to have the right temperature within the hive when the temperature of the cellar is a few degrees lower than that stated.
If the beekeeper will pay attention to the temperature of the interior of the hive he will find that in colder cellars it is desirable to give the hives some insulation to conserve the heat generated by the bees in much the same way that this heat is conserved when bees are packed outdoors, although the amount of protection will be much less. In a cellar where the temperature falls to 45° F. it will be found best to have the covers of the hives sealed on tightly and the entrances reduced to 3/8 inch by 2 inches. In a cellar with a temperature of 50° F. or more the entrances may be left open the full width of the hive. If there is a tendency for the temperature to fall to 45° F. or less, the tops of the hives may be protected by cushions of chaff or other materials placed at least on the top of the uppermost hives, for each of the lower three hives is protected somewhat by the one above it.
It will be impossible to maintain the temperatures recommended unless the cellar is built in the way described, or in some other way by which the cellar is equally well insulated. It is impossible to maintain an equable and high temperature in a cellar the walls and ceiling of which are exposed to the outside air.
If the proper temperature is maintained in the cellar there will be little need of ventilation, for in almost all cases there will be sufficient interchange of air to keep the bees in good condition. If the temperature is as low as 45° F., a little ventilation will be needed, although most of the bee cellars that have been built have had too much ventilation, and as a result it has been impossible to maintain a correct temperature within them. In cold weather the tendency toward an interchange of air is greatest, and at such times the ventilators may be entirely closed. In mild weather it makes no difference if large ventilators are open, unless this results in too great a rise in temperature.