76 



FOURTEENTH ANNUAL REPORT OF THE 



chief difficulties seems to be a lack of 

 information concerning' the interrela- 

 tionship of temperature and relative 

 humidity and it may be well to make 

 some of these points clear. 



The Source of Moisture in the Hive. 



All northern bee-keepers know that 

 under some conditions, especially in the 

 cellar, the atmosphere in the hive in 

 winter may become so laden with mois- 

 ture that it cannot all remain in the 

 form of water vapor but condenses on 

 the hive and combs. Water may even 

 run from the hive during- the winter 

 confinement. Obviously this moisture 

 does not come from outside the hive 

 for this often occurs when the cellar 

 appears dry. 



Within the hive the only source of 

 moisture is the food consumed by the 

 bees. Honey not only contains about 

 20 per cent water but when the sugars 

 are consumed and assimilated the final 

 products are carbon dioxide and water. 

 Honeys vary in composition but on an 

 average when one pound of honey is 

 consumed there is produced about two- 

 thirds of a pound of water and, since 

 honey is one and one-half times as 

 heavy as water, one gallon of honey 

 when consumed produces approximately 

 one gallon of water. 



If we take for example a bee cellar 

 containing 216 colonies and estimate 

 the average consumption of honey dur- 

 ing the winter at ten pounds per colony 

 the total honey consumed is 2,160 

 pounds or 180 gallons. This produces 

 1,440 pounds of water or 180 gallons, 

 enough to fill six 30 gallon barrels. If 

 these colonies are in the cellar for four 

 months there will be given off one and 

 one-half gallons of water a day and 

 unless there is considerable movement 

 ' of air within the cellar the atmosphere 

 cannot take it all up as water vapor 

 and condensation will occur. 



The Relation of Humidity to Tem- 

 perature. Before discussing the changes 

 which take place in the humidity of the 

 hive it may be best to take up some 

 facts concerning the moisture content 

 of the atmosphere as influenced by tem- 

 perature. It is of course well known 

 that if warm moisture laden atmos- 

 phere is cooled its capacity for water 

 vapor is decreased and moisture is con- 

 densed. This is shown in the conden- 

 sation of moisture on the outside of a 

 glass of ice water. Similarly we have 

 condensation on the surface of the 



leaves which we call "dew" if the mois- 

 ture remains liquid and "frdst" if it is 

 frozen as it condenses. These phe- 

 nomena are duplicated in Hie bee hive 

 and bee cellar. | 



The problem of the bee-keeper Is to 

 eliminate this moisture, whiich leaves 

 the body of the bee in the f orrn of water 

 vapor, without condensation.; This has 

 been done in cellar wintering (1) by 

 raising the temperature of 'the outer 

 air, (2) by drying the air (|as by the 

 use of unslaked lime in the ^cellar), or 

 (3) by causing the air to move so that 

 as the atmosphere becomes laden with 

 moisture it is replaced with! other air 

 capable of taking up more moisture. 



To determine by weight the actual 

 amount of water in the atmosphere is 

 difficult in ordinary practice and the 

 usual method is to determine the rela- 

 tive humidity, that is the amount of 

 moisture in the atmosphere compared 

 with the maximum which might be held 

 at that temperature. The common 

 method is by the use of ^ the wet and 

 dry bulb thermometers, to determine 

 how much the wet bulb; Is cooled by 

 evaporation. Then from ;this data the 

 relative humidity is'obtaiijied from pre- 

 pared tables. ; 



To make clear the relation of the 

 relative humidity to temperature it may 

 be well to choose a few examples. For 

 the first case, there may be assumed a 

 cluster temperature of 60°F. (barome- 

 ter, 30 in.) in an atmosphere which is 

 fully saturated. In this event the 

 slightest 'cooling will ^ cause condensa- 

 tion an& the wet bulb in such an at- 

 mosphere (if it could be circulated 

 rapidly) would show no cooling. No 

 evaporation can occur as the atmos- 

 phere cannot take up any more mois- 

 ture. If, however, the wet bulb can be 

 cooled at this temperature the relative 

 humidity is less as the readings of the 

 wet bulb thermometer are lowered. The 

 temperature to which an atmosphere 

 must be cooled to produce condensation 

 is known as the "dew-point". This is 

 also lowered as the humidity decreases. 

 These points are illustrated in the ac- 

 companying table: 



Assumed cluster 

 temperatures. 



Dry Wet Dew Relative 



bulb bulb point hjamidity 



60°F. 60OF. 60°F. 106 per cent 



GOOF. 580F. 57°F. 89 per cent 



60°F. 560F. 530F. 78 per cent 



