I see. Thanks guys.
I've remember I got a plastic one years ago, but never used it.
We tend to use the wooden ones here with metal mesh, and there is no cover over the candy. One of the three circles in the cage is more or less filled with candy and the bees in the hive can access the candy immediately from the hole in the end, with the queen and attendants working at it from the other side. Thin plastic covers the candy from the side, but it is under the mesh. Surely given that such covering of the candy (as in the plastic cage), is not done routinely here, it is not necessary at all?