Thank you! I'll move to the appropriate guide.

Could you briefly explain what you mean by "black T2" ? ;-)

Ah, "Muellerian ring", something new to me, thanks for that.

I'm still trying to discern between Bumble Bees and Carpenter Bees. I know for a fact that the dark tan colored ones are the Carpenters, I have plenty of photos of them. It's these lighter colored ones that I'm not so sure about.

to discern between any Xylocopa and Bombus.
- forewing venation is not the same. The marginal cell and the three submarginal cells have a quite peculiar shape in Xylocopa, while they are much more "conventional" (so far as Bees as a whole are concerned) in Bombus.
- gaster (apparent abdomen) is distinclty flatter in Xylocopa.
- in the female gender, head seen from above is almost as broad as thorax in Xylocopa, while distinctly narrower in Bombus. Compound eyes are virtually contiguous to the basis of mandibles in Carpenter Bees, while there is always a more or less broad space in-between in Bumble Bees.
Dark, somewhat reddish, fur color of young X. virginica tends to fade to pale tan as individuals are aging, hence a color sometimes quite similar to the black and tan Bombus.