> After 3 to 4 weeks, the longer the better, you can pull off the screen
> and bee escape. Your bees will go into the old hive and kill the old
> queen and rob all the honey stored in the walls
 
I know that this is what all the books say, and it may be true if there is
a dearth on when you remove the screen and the outside hives are really
strong and nasty -- and of a breed that tends to rob.  But I say YMMV.
 
If there is a decent flow on when you remove the screen after a few
weeks,  the bees in the outside hive may very well ignore the hive in the
wall and it may build back up very nicely.  The you get to repeat the
procedure.
 
Think about it:  In three weeks, all the brood laid the day you put the
screen on will have just barely have hatched out.   Of course the queen
and remaining (young) bees will have continued to raise brood for weeks
after you started removing bees, so there will still be new bees hatching
for four or five weeks after screening, and likely longer.
 
It doesn't take much to guard a hive against robbers under normal
conditions.   If the entrance hole is small, it only takes a few bees to
guard the entrance.  We often keep small nucs in the same yard as strong
colonies.  Most queen breeders of repute keep strong drone colonies near
their baby nucs to supply drones.  Robbing of the nucs is seldom a problem
until the end of the season , if at all. FWIW, I've never seen it and we
had hundreds of nucs containing only a cup or so of bees.
 
I think we are dealing here with another case of books uncritically
repeating the same questionable story without thinking.
 
Allen
 
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