88 
Beekeeping 
laying and brood-rearing may seemingly be stimulated 
either by a high or very low outside temperature. 
THE WINTER CLUSTER 
There are three possible ways by which an animal can 
survive a protracted period of adversity like a northern 
winter, when food is not available in the field and when it 
could not get food even if it were present, because of the 
cold. The first method is hibernation, in which the only 
storage of food is within the animal, and at low temperatures 
the vital functions apparently cease. This is the universal 
mode of wintering among solitary insects and, even among 
the social species, in bumblebees and wasps, the majority 
of the colony die off while the fertile queens hibernate like 
solitary insects. Ants hibernate in a mass during extreme 
cold weather. Another method is migration, but this is 
not open to most insects because of their size and inability 
to fly long distances, as do birds. If a cold-blooded animal 
cannot hibernate, as the honeybee apparently cannot, nor 
migrate, there is but one course open to it. This is to lay 
up a store of heat-producing food and, when the surround¬ 
ing temperature falls below that at which the animal can 
live, to generate heat, virtually to create a thermal environ¬ 
ment of its own. This remarkable procedure, in which 
the honeybee is unique among insects, is the one encountered 
in a study of bees in winter. Beekeepers have long known 
that the winter cluster is warm but they have perhaps failed 
to comprehend the marvel of an insect which can use this 
method of overcoming adverse conditions. 
The hoarding instinct, the instinct to store food in great 
excess of the immediate needs, now becomes of vital im¬ 
portance to the continuance of the species, but it would 
serve no useful purpose in the winter season if the bees in a 
colony did not also have the ability to generate and con¬ 
serve heat. As will be seen later, the generation of heat 
is by a method common to all insects and other cold-blooded 
