THE BEEKEEPERS' REVIEW 411 



of bees during the winter and of the effects of various environmental factors 

 on the colony. This bulletin does not include the results of this work, but 

 gives the methods of outside wintering which have proved best in commercial 

 apiaries, all the statements here made having been substantiated by the results 

 of the more detailed studies which are to be reported in other form. There are 

 many factors which require still more study and the doubtful points are noo 

 here discussed. It seems best not to include a discussion of the wintering of 

 bees in cellars, concerning which there are many more points in dispute which 

 can be settled only by detailed scientific studies. This omission should not be 

 interpreted as indicating that the authors condemn cellar-wintering; in fact, 

 they are inclined to believe that when properly worked out this method will 

 be found superior in northern localities. 



Beekeepers usually report the results of wintering by giving the percent- 

 age of colonies in which all the bees die, just as was done in the first paragraph 

 of this bulletin. This is a convenient method but is misleading. If every in- 

 dividual bee that goes into winter quarters remained alive in the spring with no 

 loss of vitality, we should have perfect wintering, but such success is impos- 

 sible. If out of 100 colonies only 2 die and the remainder are only half as 

 strong in numbers as they were in the fall, most beekeepers would consider 

 this rather good wintering, while in fact it is poor. The criterion of success 

 is to save the greatest possible number of individual bees and to have them 

 capable of prolonged activity in the spring. Beekeepers sorely need a new 

 point of view as to success with this vital problem. 



Frequently in beekeeping literature mention is made of the "winter sleep" 

 of bees. Bees can not hibernate as do most insects. While the bees on the 

 outside of the winter cluster are usually quiet, there is incessant movement in 

 the center during cold weather; in fact, the colder the surrounding air, the 

 greater the activity of the colony after a cluster is formed. The phrase "win- 

 ter sleep" is therefore erroneous and should be dropped from the literature, as 

 it misleads beekeepers. 



CAUSES OF WINTER LOSS 



The causes of the death of individual bees or of a colony of bees in winter, 

 barring unusual accidents, are only two in number: (1) Inadequate stores and 

 (2) excessive heat production. The numerous factors usually given in the 

 literature on the subject as entirely distinct fall into these two classes, except 

 for some that are usually given which the authors do not believe to be opera- 

 tive. 



Excessive Heat-Generation 



It was first shovra by the authors in the bulletin to which reference has 

 been made that at hive temperatures between about 57 degrees and 69 de- 

 grees F. a normal broodless colony of bees does not form a cluster, but the 

 bees remain inactive on the combs. When the temperature of the air immed- 

 iately surrounding the bees (not the temperature of the air outside the hive) 

 falls to 57 degrees F. or lower, they form a cluster and those in the center 

 begin to generate heat by muscular activity, while those in the outer portion 

 serve as insulators by crowding close together, usually with their heads toward 

 the center of the cluster. The innermost portion rapidly acquires a tempera- 

 ture considerably higher than that of the air about the bees before cluster- 

 ing was necesary, often going to 90 degrees F. in normal colonies and higher 

 in abnormal ones. The number of bees engaged in heat production increases 

 as the outer temperature falls and the insulating zone is consequently decreas- 



