I am observing frequently different bumble bees in my garden (Austria prealpine-alpine region). One of them that I frequently saw is all black with red-orange abdomen (tail). From a very simple schematic poster I found I had concluded it would be Bombus lapidarius, but now reading a bit more on bumble bees I find it could as well be B. wurfleini. My question is now what would be the most obvious/simple way to discern between the two species?
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