40 CONSTRUCTIVE BEEKEEPING 



calities, with a temperature of zero or lower for weeks at a time, 

 insulation is necessary to protect the bees from the cold, and in 

 spring and fall to protect them from excess of moisture. In lo- 

 calities where the cold is not so severe but that the bees can beat 

 back what little cold comes in at the entrance, insulation is neces- 

 sary to keep the hive dry. In the north we insulate to keep the 

 hive warm and dry. In the south you should insulate to keep 

 the hive dry. 



The question naturally arises as to how insulation keeps the 

 hive dry. How it keeps the hive warm is obvious. Because at- 

 mospheric vapor and temperature are so correlated they must be 

 considered together. Heat is communicated in three ways: by 

 conduction, when it travels from partical to partical in the sub- 

 stance heated ; by convection, when the particals of the substance 

 heated move away from the sourre of heat; by radiation, when 

 heat travels through space in all directions from the heated sub- 

 stance. 



Insulation has to do with heat communicated by conduction. 

 A substance that is a poor conductor is a good insulator. The 

 escape of heat from a substance or space depends on the amount 

 and quality of insulation surrounding the substance or space. 

 The fireless cooker is a good example of what insulation does. 



The wood of which a hive is made is the insulation that sur- 

 rounds the hive air. Add to this insulation a uniform thickness 1 

 of leaves, sawdust, chaff or any other insulator and you make 

 it harder for the heat to pass out of the hive by conduction. 

 Hence a well insulated hive has a temperature more nearly uni- 

 form than a single wall one. 



The temperature of a hive could easily be kept uniform if the 

 bees did not have to have air. An opening must be left for ven- 

 tilation, and because of this heat is passing out of the hive by con- 

 vection. Not much heat passes through this opening by radia- 

 tion or conduction, as air absorbs heat slowly and does not readily 

 part with it. The escape of heat where the opening is not too 

 large, is not great and the radiation and convection of heat from 

 the bees will balance that, where outside temperature is not very 

 low. Where they have both opening and single walled hives 



