The logistics of pollen
All bees have one thing in common: they use pollen and nectar to feed both themselves and their young. However, the best way to bring pollen and larvae together has been a subject of disagreement among bee species. As a result, bees have devised various ways to solve the age-old problem.
When we think of bees and pollen we usually visualize chunky pollen pellets adhering to the hind legs of a foraging bee. But in fact, certain members of the Apidae family—including bumble bees, honey bees, orchid bees, and stingless bees—are the only ones that have corbiculae (pollen baskets).
Many bees have a scopa somewhere on their bodies. A scopa is a tuft of specialized hairs that are designed to hold pollen grains. Many mining bees, for example, have scopae on their hind legs. In some species, the leg scopa is on the tibia, but in others the leg scopa is higher up on the femur. Some species of the Colletes and Andrena genera have additional scopae on the sides of the thorax in an area called the propodeum.
Going further, some bees in the Fideliidae and Megachilidae families have a pollen scopa on the undersides of their abdomens. This is commonly seen in the mason bees.
Some species in the Colletidae family (subfamily Hylaeinae) have no scopae or corbiculae anywhere. Instead, they swallow the pollen in their crops and regurgitate it much like nectar.
Then, of course, some bees have decided not to carry pollen at all—they just steal it. Instead of bringing the pollen to the larvae, they bring the larvae to the pollen. To achieve this, they invade the home of another bee and deposit their eggs on the pollen provision left by the host bee for her own offspring. These social parasites, known as cuckoo bees, are found in various families and, over time, have lost all ability to carry pollen. Cuckoos are more numerous than you might think; O’Toole and Raw in “Bees of the World” estimate that 20 percent of North American bees are cuckoos.