346 
Beekeeping 
the temperature, by abundant ventilation or by artificial 
drying, as by the use of unslakcd lime. These methods 
may be applied in the bee cellar. It should be recalled that 
an increase in the temperature of the atmosphere increases 
the capacity of the atmosphere for water vapor and thereby 
decreases the relative humidity. 1 
Bees need water in winter but they get enough in their 
food provided the temperature does not get so high that 
the relative humidity of the outer air is too low. The 
optimum relative humidity has not been determined and, 
in fact, virtually no observations have been made on the 
relative humidity of the atmosphere of the hive or bee cellar. 
Probably the great diversity of opinion as to the best tempera¬ 
ture for the bee cellar is due to the unrecorded differences 
in the relative humidity of the various cellars observed. 
Effects of ventilation. 
Ventilation of the hive and of the bee cellar depends upon 
the currents of air caused by the differences in temperature 
in two points, since bees do not mechanically ventilate 
the hive in winter. The movements of air serve not only 
to remove carbon dioxid and bring in oxygen but, probably 
more important, they carry out the surplus water vapor. 
Abundant ventilation is beneficial and becomes harmful 
only if the temperature is too greatly reduced thereby. It 
has been determined that bees survive in an atmosphere 
which contains an unusually high percentage of carbon dioxid 
but it is not wise to err on that side. 
Source of heat and effects of changes of temperature. 
It has been determined by Demuth and the author 2 that 
bees generate heat in winter by muscular activity and that 
1 The beekeeper interested in cellar wintering will do well to consult 
Marvin, 1912, Psychrometric tables, Weather Bureau Publication 235 
and other works dealing with the relation of relative humidity to tempera- 
i ture. 
» Phillips and Demuth, 1914. The temperature of the honey bee cluster 
in winter. U. S. Dept, of Agric., Bulletin 93. 
