One of mine went queenless last summer then very hard to manage - it had always been tetchy. Uniting with a nuc via the flour method wasn't successful (I should have known) so the other spare nuc went above newspaper on a QX over the supers over a queenless brood box of very wound-up bees. Super bees are known to be more welcoming. They united peaceably after the QX was removed a week later, and another week later the nuc was moved down to the centre of the old brood box.

Excited bees in early summer can be hard to requeen. There is something to be said for doing the requeening in late summer if possible.