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Date: | Thu, 30 Nov 2023 19:05:11 -0800 |
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> But I have noticed that on hot, humid evenings with the heaviest
bearding, the bees often cover all but 3-4 inches of the Langstroth entrance
That was something that impressed me when I first visited the Midwest on a
hot, humid day -- there were only a few tiny air passages left through the
cluster.
Clearly, the bearding was not due to inadequate cross-sectional ventilation
openings.
This something that impressed me when I first read (back in the 1950s) Knut
Schmidt Nielsen's research on how camels survive hot weather. I just
looked up his article in
Scientific American from 1959, from which I quote:
"People in desert areas and outside them have long appreciated the
excellent insulating properties of camel hair. The camel employs camel-hair
insulation to lower its heat load still further. Even during the summer,
when the camel sheds much of its wool, it retains a layer several inches
thick on its back where the sun beats down. When we sheared the wool from
one of our camels, we found that the shorn animal produced 60 per cent more
sweat than an unshorn one. To Americans, who wear light clothing during the
summer, the idea that a thick layer of wool is advantageous in the desert
may seem unreasonable. The Arabs, however, typically dress in several
layers of loose clothing, frequently made of wool. I have seen a nomad
returning from the desert shed one thick wool burnous after another. We
ourselves quickly learned that Arab dress was more comfortable than
"civilized" garments."
This opened my mind at a young age that dark insulation is a great
protection from heat (by dark I mean material that absorbs and
re-radiates IR light, rather than conducting that heat inward). This was
supported by my observation that the Mexicans in California working
outdoors often wore dark sweatshirts in the heat. I've also observed that
it works the same with soil solarization -- a covering of black plastic
keeps the soil cooler.
So I'm not surprised that bee colonies in insulated hives find it easier to
deal with solar radiation and hot ambient temperatures. By moving the
metabolic heat of the adult workers outside, the remaining workers can more
easily keep the brood from overheating via evaporative cooling -- depending
upon water foragers to bring in water to evaporate. They can use
evaporative cooling until the dewpoint temperature approaches 95F, although
cooling becomes more difficult as the dewpoint rises.
Randy Oliver
Grass Valley, CA
530 277 4450
ScientificBeekeeping.com
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