Some time back there was a thread discussing feeding of syrup of
varying 'thickness'.  I finally came across a few articles that I had
been reminded of.
 
Murray Reid, AAO from New Zealand (who reads and posts to this list)
summarised a lot of the existing research back in the May 1974 issue
of the New Zealand Beekeeper, pages 41-43:
 
Summary of that article -
 
Bees must invert or 'digest' sucrose molecules and reduce the water
content before storing.  With dry sugar, bees must add considerable
water first.  He quotes Simpson as saying that if sugar content is
greater than 59%.
 
Enzymes (particularly invertase) needed for reducing molecules are
from hypopharyngeal glands (same as for producing royal jelly for
larvae and queens).  Nosema affects these glands.  Refers to Russian
reserach correlating honey production of hive to efficiency of enzyme
production by bees.
 
Converting sugar into 'honey' is exhausting process in terms of
energy.  Must produce enzymes, secrete them, suck up syrup, invert
it, keep hive temp high to help evaporate extra moisture, as well as
secrete and manipulate the was to store it in.
 
Wedmore calculated 60-70% of heat generated from eating stores is
used for heating the bees, 20% to evaporate the extra moisture, 10%
to heat the air.
 
Ribbands estimated the energy (heat) needed to evaporate 1 lb of
water at 4-5 oz of sugar.  (25%, compared to 20% estimate by Wedmore
above).
 
Consumption of honey also releases water (as honey is 17-18% water).
Some of this lost through rectum in cleansing flights.
 
One pound beewax can give 35,000 cells, and hold 22 pounds of honey.
Estimates give 6-10 pounds honey to produce 1 pound wax, so
significant amount of original sugar stores will be used to produce
the wax and maintain high cluster temperature needed to manipulate
wax.
 
Case study:  Let's feed 4 gal of 2:1 or 62% white sugar syrup.  32
pounds sugar at the rate of 16 pounds/gallon and will weigh 52 pounds
or so.  Assume 18% moisture for the ripened stores, will need to lose
20% water or about 10.4 pounds.  This equals elimination cost of
nearly 3 pounds of sugar, if 4-5 oz are lost per pound of water
evaporated.  This sugar, when consumed, will also release extra water
requiring energy to eliminate...
 
Bees will use 5-9 pounds of honey or sugar to build the wax to hold
the syrup.  From original 52 pounds of syrup, we have lost or used
10.5 pounds of water, and say 11 pounds of sugar.  Now have about
30.5 pounds of ripened stores.
 
Rule of thumb for ripened stores in comb is slightly less than the
dry weight of the sugar going into the original syrup.  In this case
30 pounds stores from 32 pounds sugar.
 
Recommendations:  Don't leave sugar feeding too late in autumn.  Feed
while: (1) there are plenty of older expendable bees with active
glands still present (2) it is not too cold to secrete wax (3) it is
not tool cold or damp for efficient evaporation of moisture from hive
(4) there are still some natural honey stores in the hive.
 
"BEES DO NOT FREEZE TO DEATH - THEY STARVE TO DEATH"
 
  (\      Nick Wallingford
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