How the honey bee makes pollen pellets
A honey bee has three sets of legs, and each set is different. The last two legs—the hindlegs—are designed to compress and carry the pollen pellets that are characteristic of honey bees and bumble bees.
We’ve all seen those hard round nuggets in various colors and sizes, but did you ever wonder how the bees pack the pollen into a ball? Well, the secret tool is called a pollen press. The pollen press is actually made of two flat plates that are hinged together. One plate is on the distal end of the tibia, while the other is on an adjacent segment called the basitarsus.
If you lined all the leg parts end to end, starting at the thorax you would see:
However, the tarsus is further divided into several sub-segments: the basitarsus and four small tarsomeres.
What I have shown below is the joint between the tibia and the basitarsus, because that joint is the pollen press.
When the joint is bent, the plates pull apart and the bee stuffs the opening with pollen that she collects from her body. First, she uses all six legs to scrape the pollen into one place: the inside of the hindleg basitarsus. Then she combs it off the basitarsus with stiff bristles on the edge of the pollen press called a pollen rake. She cleans the left with the right and the right with the left, until the open press is full of pollen.
When she straightens her leg, the plates close against the pollen and force it up into the pollen basket. It’s like a tube of toothpaste: when you squeeze the two sides together, the paste comes out the top. Here, when the two plates are squeezed together, the pollen is forced up into the pollen basket. Although it may seem backward, the pollen basket is actually filled from the bottom.
Every time the bee grooms the pollen from her body, she works the pollen down to the inside of the basitarsus of the rear legs and then into the press before she gives it another squeeze. Is that cool or what?
The leg part shown below was taken from a dead honey bee I found in my driveway. She had one of those cards that said, in case of her death, she was leaving her body to science. RIP.