Many thanks to all those who responded, the answers were most informative 
and I will now experiment with provisioning the cages with honey and pollen 
to see whether that makes a difference.

I asked Thorne's for their views and they thought that the bees would feed 
virgins through the mesh, a view shared, I note, by Larry Connor in his 
article in the August ABJ.

The question was asked: why would anyone want to bank virgins?  This perhaps 
a natural question for a large-scale producer to ask as he will always have 
surplus cells to hand.  However, for a small-scale producer like me, rearing 
cells takes a significant amount of time and effort, so good 'spare' cells 
are very valuable, especially when it might be possible to use the virgins 
within a few days.
Our beekeeping operation has just two 'employees' - my wife and me - and 
sometimes events (such as the wonderful English weather) may conspire to 
make it impossible for us move mated queens on from mating nucs in time for 
us to distribute cells on the tenth day as planned, so again we might want 
to bank the virgins, if only for a day or two.
We may also wish to distribute surplus virgins to other members of our 
association and this again might require us to hold them for a short while.

Best wishes

Peter
52.194546N, -1.673618W 

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