Gert :
 
Since no one else has tried to answer this question i'll try (caution, some
of what I write might be bullshit).
 
At 08:43 AM 4/23/97 -0700, you wrote:
>We're still waiting for a response on this one.
>
>Query to all:  Can anyone describe what happens to individual bees in
>cool/cold temps.
 
There is a review of honey bee thermoregulation in Bernd Heinrich's 'Insect
Thermoregulation' (Heinrich of 'Bumble Bee Economics' fame.  Somewhere in
his review I think he said something like this : honey bees can generate
heat by 'uncoupling' their wings and shivering.  As I remember it, when
ambient temperature falls below -5 celsius clusters reach their maximum
density and the bees actively generate heat by shivering (and no bee gets
colder than 8 celsius for very long - apparently a lethal temperature for
honey bees). So the cluster remains warmer than ambient at sub-zero celsius
temperatures.
 
>The bees cluster at 57 degrees, but they obviously fly
>at lower temps.  Also the inside of the hive must be much warmer than
>outside at that temp range.  As the temp goes down, do bees have less
>flying time.  Are they "warmed by the cluster" and are they then able to
>fly for a short distance for cleansing flights etc.  At what temp does
>their flying activity fail to keep them warm enough so they don't make
>it back to the hive?  Gert Walter
 
I think so, to a point.  When it's too cold I guess even the heat generated
by beating
wings is lost so quickly that the bee's muscle temperature falls below some
minimum needed to beat, and the worker plummets into the snow bank.  There
must be a minimum muscle temperature that must be maintained by the flight
muscles to keep a bee in flight.  I would guess its somewhere around 25 C.
Probably the flight temperature limit of bees is around 12 C ambient because
this is the lowest temperature at which despite heat losses they are able to
keep their flight muscles above this critical flight muscle temperature (25
C - a guess). If all this is correct, bees should be able to take short
flights below 12 C provided the cluster is warm enough to bring them up to
flight temperature.  They must return before they loose all their heat and
sieze up when flying below these temperatures.
 
A half-baked, poorly expressed idea... and my dinner has gotten cold after
all that thinking and typing.
 
Cheers
Adony
 
 
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