BOTTOM PACKING.
There has been considerable discussion among beekeepers as to the value of placing packing material below the bottom boards of the hives. This is usually provided by placing the hives on 2 by 4 inch supports or on racks of 4-inch material. Those who have opposed this have pointed out that "heat rises," overlooking the fact that while warm air attempts to rise, if this is impossible other avenues of escape of warm-air currents may be set up. Furthermore, and more important, they have overlooked the important fact that heat escapes from the hive not only by convection currents but by conduction and radiation as well. In an extensive series of experiments performed by the writers it was found that in hives packed at the top and sides most of the heat escapes through the bottom boards; in fact, this was so noticeable that the packing at the top and sides never served its full purpose so long as heat was escaping rapidly at the bottoms. It may be stated, therefore, that so long as the bottoms are unprotected there is little insulating value in materials piled on the top and sides beyond about 2 inches. This amount is insufficient for most parts of the United States, therefore bottom packing should be considered as absolutely essential wherever bees are packed.
To get the value of bottom packing it is absolutely essential that the entrance be reduced, but it need not be closed. In a long series of temperature readings on hives packed for several winters, the authors were able to keep a temperature of 50° F. on the bottom boards of packed hives directly behind the entrance openings. Those who have condemned bottom packing have labored under the mistaken notion that it is impossible to prevent currents of cold air through the entrance. This is entirely possible if the entrances are adequately reduced. The conclusion to be drawn from the experiments performed is that unless the bottoms of hives are well packed, the beekeeper ought not to imagine that he has packed his hives at all well.
Fig. 2.—The winter packing cases used in the Bureau of Entomology apiary: a, Detail of tunnel to hives. In the specifications given in this Bulletin ([p. 9]) provision is made for room for a third hive body to be added in the spring.