Many years ago, I was sitting outside looking at some bees feeding on flowers that were growing in hanging planters. I knew from taking apart previous hanging planters that there are sometimes a lot of plastic pellets in there, or sometimes very lightweight material that is the color of dirt but not with the same density. I thought to myself that the bees were expending a lot of time and energy getting nectar and pollen from the flowers in the hanging planters. But what kind of nutrition were they getting in return?