>Why would bees move a larva when then can easily make a queen cell from a 
>worker cell?

Good point.

If we are talking about which can be easily achieved,,,
If the colony needs to create a queen cell from
a worker cell, this could take time depending on
the age of the comb.  This time could cause a 
deficit of nutrition to the queen larva, and it
may have ill consequence to her health, and 
subsequently impact the colonies survival.

Easier, would be the simple transfer of a larva 
or egg to a more 'appropriate cell' or 'play cup', which 
depending on breed are sometimes present and ready
for immediate use by the colony. 

At one time I kept Russian bees.  I observed a 
habit of Russians building comb by incorporating
bits of debris into the comb.  This would IMO 
strengthen and speed up the aging and
hardening of the comb somewhat.  

One might hypothesize that Russians keep many 
play cups due to the labor and time required to tear 
down and reconstruct hardened comb into queen 
cells in the event of an emergency. 

Increased time constructing queen cells from 
worker cells and delay time in supplying 
abundant food ='s increased risk.  It 
would be logical for bees to hedge against 
this risk by implementing a strategy when needed,
of moving eggs or larvae to more appropriated
places.

Best Wishes,
Joe Waggle

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