This Buff-tailed bumblebee (Bombus terrestris) is having a productive day, you can see that her “pollen basket” (the real name is corbicula) is almost full 🙂
The basket is the bumblebee’s storage, it’s made out of hard hairs on the flat part on its back legs. When she walks around in the flower, pollen is collected all over her body and then she sort of “combs” it into the basket. Only nesting female bumblebees collect pollen, the males don’t have any baskets.
Zoom in on the basket: