The plants in our backyard attract a lot of insects and we get plenty of bees hanging out on sunny days.  One of our hanging baskets gets a reasonable amount of attention but not a lot.  However, one bee showed up on a Sunday afternoon and got our attention.  First, it stayed on the basket for ages climbing over the same flowers repeatedly unlike the usual bee behavior or constantly moving from flower to flower.  The other reason for our attention was the size of the thing.  It was huge compared to our average bees.  I wonder if it got so large by removing every morsel of nutrient from each flower!