I have been having such fun reading Dave Goulson's 'Gardening for Bumble Bees' book. I had to finish a rather uninspiring online course before I could start it, but it was worth the wait.
I've only got to page 64/5 so far but have learned not only about Bumbles but also Solitary Bees and my little pals the Hover Flies. There is one Cuckoo HF which 'flicks' its eggs into a host Miner Bee's nest tube so they hatch into larvae which mooch about eating detritus in the nest until they hatch into new adults, no harm done to the Solitary bee. Another lays its eggs in a flower so the hatched larva hitches a ride on the host bee to get into the nest. Not all just do the cleaning, some do predate the host bee's young.
I no longer fear identifying the most numerous queens- there are only half a dozen or so which get as far north as me anyway.
The only Scottish BB is the Great Yellow BB which was found recently in the far north, so I'll not be seeing that in my garden either.
Dave Goulson's book is only about £12 for those who can bring themselves to buy from Amawotsit and it's well worth that cost