Bumblebee with 'Pollen Baskets' (or corbiculae) on a Blanket Flower (I.D. courtesy of Peter May)
Again, not strictly a "Zoo" picture, but outside the Sonora Desert exhibit, there were these beautiful plants, with bumbleebees busily gathering pollen. They had these brilliant orange Pollen Baskets on each side of their bodies that attracted my interest. Canon 100/f2.8, ISO 100, f/4.5, 1/500 second (hand-held).