Orchid bees use their extraordinarily long tongues to drink nectar from the deep, tropical flowers only they can access. Researchers have long suspected that this kind of exclusive access came with a mechanical cost. According to common sense and a classic law of fluid mechanics, it's just plain hard to suck thick, viscous nectars up through a long straw.
A paper in The American Naturalist confirmed this prediction for the first time in 2007: orchid bees with long tongues suck up their nectar more slowly than bees with shorter tongues.
Scaling of Nectar Foraging in Orchid Bees