The workers are learning it by «learning by doing». They have to learn it when they leave for the first time. Only for the queen we made this training (closing it every day a little bit more), her workers are learning it very quickly. Some workers are learning very quickly, others will need more time. Or a sister will open it while the other bumble bee is trying to open it.
The bumble bees make also some pheromon markings on the Klappe so every bumble bee knows where to enter.
You only have to make sure that the entry is not going wet (it will stick) – that is why the bumble bee nest must be rain protected – and nothing is between the Klappe and the entry (pollen, other small stuff etc.) otherwise the Wachsmotte will be able to enter.
On youtube, there are some Klappen-Movies (Wachsmottenklappe)…
Themenübersicht öffnen: check the nest