The tongue is measured as shown
I feel that we beekeepers may have misled ourselves by believing that longer tongues are desirable and beneficial.
I currently think that the tongues vested in the different strains allow the forage plants to be divided up between the different species and strains of bee to reduce competition.
I think that the historical overemphasis on the honey gathering potential of the longer tongued strains has led us down a 'blind alley' in the pursuit of length for length's sake.
By having longer tongues we are probably excluding our modern strains of bee from crops that they would have foraged on in the past. The pursuit of the larger crop has therefore introduced an instability that would not have occurred without man's intervention. I am unlikely to be able to follow this up... So it may well be suitable for a research project at a college or university.