This was taken using the 50mm prime and an EF 12mm extension tube.
This was cropped quite heavily as the sharpness of this lens when you get the focus right is just awesome. I took a few of bees but this was the only one with the focus spot on, unfortunately he was facing the wrong way!
Focus on the bee is indeed spot on, nice job. Unfortunately those bees don't always pose nicely with their heads facing the camera -- very rude of them.