I built such bumblebee houses a few years ago with the kids. The flap is essential against a kind of flies that lay their eggs in the bumblebee nest and their caterpillars eats the nest. Either the Queen or the others learn the usage quite fast. Sometimes next generation queens remember it in the next year
That's so cool! I have to try this with my kids. They will almost certainly not care, but what the hell.
Are you saying that a queen will die and its successor somehow knows how to use the door without learning like its mother had to?