When you see bees flitting about your garden, you might notice that some of them have orange or yellow clumps along their hind legs. Resembling tiny saddlebags, these bright spots of cargo are pollen baskets or corbiculae. These baskets are found in apid bees, including honey bees and bumblebees.
Pollen sticks to bees each time they visit flowers. As the Adirondack Almanack points out, "It sticks to their antennae, their legs, their faces, their bodies. They become one giant pollen magnet."
A bee's legs have an array of combs and brushes. As she becomes laden with pollen, a female bee uses those tools as grooming devices, running them through her body and hair to pull away the pollen. As she brushes herself, she draws the pollen toward her hind legs into those little pockets.
As a bee gathers a batch of pollen, she pushes it into the bottom of the basket, pressing it tightly into what's already there. A full basket can carry as many as a million grains of pollen.
She mixes a little nectar with the pollen to make it sticky and to help it hold together, says the Honeybee Conservancy.
Researchers investigated to see what keeps the pollen baskets from falling when the bees take flight. In their study, they tugged on some of the bees' baskets using elastic string and were surprised at how firmly the pockets stayed attached. They found that long hairs on the bees legs kept the baskets firmly in place.
Other species of bees have something similar called a scopa. It has the same job, but instead of being a pocket-like structure, it's a a thick mass of hairs and the bees press the pollen between them.