The Bumble Bee Conservation Trust has produced identification sheets of the most common garden bumble bees.
I enthusiastically recommend you look at them if you have ever wondered what the name of that huge bee bashing itself against the window is called - I know I have ;-). The sheets are very clearly laid out with simple information and lovely illustrations.
In case of just such an emergency I have printed them out and blue tacked them by the garden window.
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