OUTDOOR WINTERING OF BEES. o 
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 operative. 
EXCESSIVE HEAT-GENERATION. 
It was first shown by the authors in the bulletin to which reference 
has been made that at hive temperatures between about 57° and 
69° 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 immediately surrounding the bees (not the temperature of 
the air outside the hive) falls to 57° 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 temperature con- 
siderably higher than that of the air about the bees before cluster- 
ing was necessary, often going to 90° F. in normal colonies and 
higher in abnormal ones. The number of bees engaged in heat pro- 
duction increases as the outer temperature falls and the insulating 
zone is consequently decreased in thickness but becomes more com- 
pact. The entire cluster becomes smaller as the outer temperature 
falls. 
If bees can be kept in an environment such that the temperature 
of the air immediately surrounding them is 57° F. or slightly above, 
they are saved much unnecessary and unprofitable labor. To the 
theoretical objection that bees need exercise, it is necessary only to 
state that the authors have so wintered bees in a cellar as well as 
outdoors with wonderfully successful results. If bees are kept in a 
cellar under the best conditions the results are excellent, but it is 
not proposed to discuss this more complicated phase of the subject 
here. If wintered outside in a packing case with abundant insula- 
tion, any heat generated escapes slowly and the temperature of the 
air in the hive rarely falls below 55° F. If inadequately protected, 
the temperature of the hive can not be kept so high and the bees 
must generate much more heat. In single-walled hives it is common 
for the temperature of the air around the cluster to fall to freezing 
or lower, in which event the bees generate an excessive amount of 
heat and perhaps die when they are no longer capable of the neces- 
sary muscular activity. The necessity of packing is thus made clear, 
and in any locality in which the outer temperature often falls to 
40° F. or below it is desirable to protect bees to conserve their 
vitality. If the temperature should fall to 40° F. only a few times 
during the winter, this would not be serious enough to make insula- 
