Bee colonies should not be left without a queen. If the queen is lost during winter or early spring, the colony has to be turned into a queenright colony as soon as possible. This can be done easily by introducing the queenless colony into a queenright colony. At the beginning the two colonies should be separated by newspaper for example, so that they slowly become accustomed to one another. The newspaper should have a couple slits cut into it to help the bees remove the paper within a few days. Or if you have extra queens in a small nucleus in indoor wintering, you can unite one of them with the queenless colony.