It had been my observation that colonies in dark hives were “better” in the
spring that white painted hives.  I was curious what effect hive color,
bottom hive heat and sun had on the bee colony behavior.  In 1976 I did a
temperature test on two dark colored hives to see how the bees would behave.
Location: Lynnwood, WA, about mid way between Seattle and Everett
Washington, USA.  The hives were two story deeps with true to color
Caucasian bees. The bee clusters were about 14 deep Langstroth combs covered
with bees at 60 F. (15.5 C). Both pine hives were setting on six inch
concrete blocks with a landing ramp at the entrance. Both were painted with
a creme colored undercoat of latex paint and then two coats of green latex
paint. The green color was called pine green. It was a darker green than
grass green and very close to a pine tree needle color.

We made a hive heater from an old western super by cutting a door on one
side that was hinged. On the other inside, I mounted a light socket to hold
a light bulb. The heater was painted the same as the hives. The heater box
was placed on a piece of 1/2 inch exterior grade plywood. I used a 60 watt
light bulb in the heater. The light was on continually during the
test except for a brief period one night when the bulb burned out and was
replaced the following morning.

The hive bottom board above the heater was quarter inch exterior grade
plywood with 3/8 inch hive entrance. The other hive had a standard
reversible bottom board with the 3/8 inch entrance in use.

I tracked the temperature in the two hives three times per day (8 a.m.,
noon, and 4:30 p.m.) for three months from mid December to about mid March.
I used a long stem (10 in.) thermometer with a round dial. I can't recall
the range of sensitivity exactly but it was below freezing on the low end
(32F, 0C) and maybe 150F (65.5 C) at the high end. The sun was able to
strike the hives from about 10 a.m. to 2 p.m. on the days it was not cloudy.

Method used:
1) Place the thermometer into the middle of the hive entrance until the
needle stabilized, take a reading and note it in the field notebook.
2) Place the thermometer into a small hole (the stem diameter) between the
two brood nest boxes into the cluster of bees and note temperature as above.
3) Place the thermometer under the inner cover with the end of the stem just
above the cluster of bees, and note the temperature in the notebook.
4) Both hives (heated and unheated) were tested in the same manner with the
same thermometer.
5) Take the ambient temperature reading of an outdoor/indoor thermometer and
record it in the field notebook.

Results:
The temperature under the cluster was always the outside or ambient
temperature (even with the heater on). The lowest temperature measured in
the center of the clusters was 48 F. (8.88 C.) even though we had 2-4 inches
of snow on the ground in the vicinity of the hives for several days in
January. The temperature above the clusters was always 10 F. above the
ambient temperature no matter the time of day the reading was taken. The bee
cluster never touched the hive walls during the test. They were at most
between frames 1 and 2, and 9 and 10.

The temperature in the cluster of the heated hive was always between five to
ten degrees above that in the unheated hive. When the sun hit the side or
front of the hives during the day, the bottom and top temperature readings
remained as stated above. Several additional readings showed that the
cluster temperature went up within 15 minutes after the sun touched the side
or front of the hives. Even though the cluster temperature was up in the
60's F. (>15.5 C.) the top temperature remained ten degrees over ambient
temperature. When the days lengthened in mid February (brood rearing seen)
the cluster temperatures remained higher even though the ambient temperature
might drop to 40 F. (4.4 C.) in the morning or evening.

When the ambient temperatures reached 55 F. (12.7 C.) to 60 F. (15.5 C.) the
bee clusters started to loosen and the top readings would go up during the
day but would remain at ten degrees above ambient temperature in the morning
and evening. At 65 F. (18.3 C.) ambient temperatures the readings were
discontinued because the clusters were usually loose and we considered
winter to have past.

The heated colony used about three less combs of honey during the winter
than the unheated colony. It also had about three more combs of brood by
early March than the unheated colony. Both colonies appeared to cluster with
the same density, and were quiet on the comb when they were manipulated the
previous fall and in late February.

Deductions:
a) The bee cluster was able to control the escape of heat at the top of the
cluster between 32F and 60 F.
b) The temperature at the bottom and sides (though not measured) of the bee
clusters was not affected by the sun striking the hive, or the hive heater,
during the reading activity.
d) The radiant heat from the sun and hive heater was absorbed by the cluster
of bees through the wood of the hive and bottom board, during the winter,
without changing the heat loss above the cluster.
e) Perhaps the wood hive is less of an insulator for the cluster and more of
a wind and weather protector.
f) Perhaps the exterior hive color doesn’t affect the hive temperature as
much as it does the bee cluster temperature and the bee energy needed to
maintain colony temperature.

Other observations over the years suggest that a dark green hive will winter
better i.e. with less use of honey stores, and larger clusters than white
painted hives.  In one apiary (in April), consisting of white, light gray,
and dark hives the beekeeper was surprised at the temperature difference to
his hand on the sunny side of the hives when he put it on the three colors
of hives.  As we opened the hives we observed that the darker hives all had
more bees in them than the white and gray ones.  When asked, he thought they
were all about the same size clusters going into the winter.  This hive
color affect is also visible during spring pollination activities where both
white and unpainted or stained hives are operated by the same beekeeper.
One beekeeper here stained a hundred or more new pine hives with cedar lids
with a dark wood color and compared them from May (as splits) to the
following June to see how hive color might affect cluster size and bee
flight during marginal pollination weather.  Colonies in dark hives were
larger and flew better at cooler temperatures in the spring than his white
ones.

It would be nice to compare white and green hives under the same conditions
using the above methods.

James C. Bach
[log in to unmask]