8 FARMERS’ BULLETIN 695. 
to do so safely. If bees fly at low temperatures (45° to 50° F.), it 
is an indication that they need a flight because of an accumulation 
of feces from poor wintering, and does not at all indicate too high 
an inside temperature because of too much packing. In conclusion, 
the beekeeper can not apply too much insulating material to a hive. 
Tt has been found that, even with abundant insulation, the tem- 
perature within the hive and outside the cluster is greatly reduced 
if the packing case is exposed to wind. During the winter 1914-15 
a record was kept of wind velocity directly over a heavily packed 
‘ase (with entrances 2 inch by 8 inches), and it was found that a 
wind with a velocity of 20 miles per hour directly on the case re- 
duces the temperature within the hives practically to that observed 
in an unprotected hive. The beneficial effects of the insulation were 
therefore nullified, and the proper temperature within the hive was 
not regained for several days unless the outer temperature rose con- 
siderably. Beekeepers have long emphasized the importance of pro- 
tection from wind, but the results observed were much more pro- 
nounced than was anticipated or than has ever been suspected by 
practical beekeepers. The ideal toward which the beekeeper should 
work is to keep his colonies during cold weather absolutely protected 
from wind, for here again the protection can not be teo great. It is 
entirely erroneous to assume, as some have done, that such protection 
is not essential in well-packed hives. 
There are several types of hives on the market in which the insula- 
tion is built in, to be retained throughout the year. There is no 
objection to the packing in the summer, except that such hives are 
not convenient for moving and in some other manipulations. Insula- 
tion in commercial double-walled hives is by means of air spaces or 
insulation, such as sawdust, chaff, broken cork, or shavings. These 
hives are better for outside wintering than single-walled hives in any 
part of the United States, but they do not provide adequate insula- 
tion at temperatures below about 40° F. Such hives must, of course, 
be protected from wind, or they are for the time being no better 
than single-walled hives. 
Types of insulation.—Various materials are used for insulation. 
Beside those named above, paper, dry leaves, and many other sub- 
stances are in use. Most of the common insulating materials depend 
on small confined dead-air spaces for their insulating value, and. 
in general, the more finely divided the air spaces the more efficient the 
material. Sawdust is usually condemned, because if moisture escapes 
from the hive into the packing it is retained and the insulating value 
is reduced. However, if a colony is sufficiently packed, moisture 
does not condense, except possibly at extremely low external tem- 
peratures, and this objection to sawdust is removed. From observa- 
eo 
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