On my first visit to the National Botanic Gardens I tried to capture the bees in these pink flowered trees, and it was a miserable failure. I used the lens wide open at f2.8 which resulted in no depth of field and mostly blurry bees.
The second visit I stopped down to around f8 which proved to be the best balance between depth of field and shutter speed to freeze these guys. It is without a doubt one of the most challenging subjects to photograph as they are constantly moving.