Certainly in an emergency I've seen the bees building queen cells around anything from new laid eggs to 4 day old grubs. In an emergency (which over the millenia could be of any source from volcanoes to beekeepers) the soundest strategy for the bees would be to get themselves a queen as quickly as possible - if she were to turn out not very good they could always supercede her at their leisure. The fastest way to a functioning queen must be to use the oldest grub which will yield a working queen - maybe this is the reason for starting with ageing grubs. Anyone got any idea of the oldest grub that will produce a functioning queen? Alan Riach - Edinburgh