I am familiar with using a frame with eggs to test a hive for the presence of a queen. But I cannot remember what I have read regarding it's usefulness in testing for a virgin. Are her pheromones adequate to keep them from starting Q-cells or is that only true of a mated queen.
A few days ago I swapped the location of a small hive with 2 failing nucs....it worked great for the nucs, but today when I went through the small hive I moved to check for stores (now that their foragers are gone to the nucs) I found they had recently superceded the old queen. 8-9 Q-cells torn open and 1 showing emerged. I did not see the new queen, there are no eggs, but some pretty small larva, the open q-cells are all looking pretty fresh, and 2.5 weeks ago I saw nothing of note in this hive....so I think this all happened pretty recently
It's quite possible I doomed the new girl when I switched hives, I assume if she was out or had already oriented to that location she would get balled upon returning to the nucs (they had their new queens today). I was short on time when I made the switch but lesson learned: Don't move without looking inside first!
Or she could well be in the hive still getting strong and will mate in the next few days....if I am lucky.
or she could be mated and in the hive getting ready to lay.....again if I am lucky
The hive had virtually no pollen, but with so little open brood I am not too worried about that. Nonetheless I was thinking of giving them a frame of pollen with some eggs if I can find it as an insurance policy.