- Re: Nelson & Bombus tongue length
You might find the following useful as a start for many species:
Medler, J.T. (1962) Morphometric analyses of bumblebee mouthparts. Transactions of the 11th International Congress of Entomology, Vienna, 2, 517-521.
Medler, J.T. (1962) Morphometric studies on bumble bees. Annals of the Entomological Society of America, 55, 212-218.
Natural History Museum, London, UK