Re: Black bees?
Black bees with no stripes often just means - old forager bees - all it is to it.
They have worn out the lighter hair and look much darker compared to the young bees (of exact same exterior).
Old forager bees are by trade the scout bees and are scanning the area for any easy loot they can find, among other things (including any drippings and such).
I would not immediately assume these are, indeed, very dark bees from some different source.
Former "smoker boy". Classic, square 12 frame Dadants >> Long hive/Short frame experimentation.