That's what happens when you mix them. They treat one as the office/ city home and the other as the vacation/ country home. You'll find them in one place or the other but not both. 
:lookout:
Seriously, I have no idea but I'll vote for swarming too. Was the queen you introduced marked? Can you tell if she's the one laying in the TBH? Top bars will sometimes swarm on a whim, even with plenty of space they'll decide not to expand but rather to split. What do you mean by plenty of space in the Lang? Did they have partially drawn supers? Some hives are reluctant to go through a queen excluder, it takes them a while to accept that space in the super.
:lookout:Seriously, I have no idea but I'll vote for swarming too. Was the queen you introduced marked? Can you tell if she's the one laying in the TBH? Top bars will sometimes swarm on a whim, even with plenty of space they'll decide not to expand but rather to split. What do you mean by plenty of space in the Lang? Did they have partially drawn supers? Some hives are reluctant to go through a queen excluder, it takes them a while to accept that space in the super.
