When a bee pauses during a flower visit, it often performs a flurry of activity involving the rubbing of its hind legs. This action is a sophisticated mechanism fundamental to the bee’s survival and the successful functioning of its colony. The primary reason for this motion is to gather and securely pack pollen, the hive’s protein source, onto specialized structures for transport. This coordinated movement turns loose, powdery pollen into a transportable pellet.
The Process of Pollen Collection and Packing
As a foraging bee moves through a flower, it becomes dusted with thousands of microscopic pollen grains sticking to the dense, branched hairs covering its body. This scattered pollen must be systematically brushed off and consolidated before the bee can fly it back to the hive. The bee uses its forelegs and middle legs as brushes to sweep pollen from its head, thorax, and abdomen, directing the material toward its hind legs.
The middle legs then transfer the pollen mass to the inner surface of the hind legs, where the true packing process begins. This material is often moistened with regurgitated nectar or honey to create a sticky consistency that holds its shape. The bee rubs its hind legs together in a precise, scissor-like motion to compress this loose, damp mass into a solid pellet.
The bee uses one hind leg to scrape pollen from the other, pushing the material into a dedicated press-like joint. Each time the hind legs are rubbed and squeezed together, a small amount of pollen is forced upward and outward. This repetitive action gradually builds the characteristic, often brightly colored, round pellet visible on the bee’s outer leg. This method allows the bee to carry a significant load, sometimes weighing nearly its own body weight, back to the colony.
Specialized Leg Structures for the Task
The ability to perform this packaging depends on the unique anatomy of the worker bee’s hind legs. The primary structures involved are the pollen press and the corbicula, which function as a highly efficient collection and transport system. The pollen press is an apparatus located at the joint between the tibia and the first segment of the tarsus, known as the basitarsus.
This press consists of two flat plates: a rake-like structure called the pecten, lined with stiff bristles, and a smooth plate on the basitarsus called the auricle. When the bee flexes its leg, these two plates clamp down on the loose pollen, squeezing it. The compressed material is forced out of the joint and onto the outer surface of the tibia.
This smooth, concave area on the outer tibia is the corbicula, commonly known as the pollen basket. The edges of the corbicula are fringed with long, stiff hairs that curve inward, securing the newly formed pollen pellet. With each squeeze of the pollen press, the pellet grows larger, held in place by these surrounding hairs until the bee returns to the hive.
Leg Rubbing for Personal Hygiene
Beyond pollen packing, the rubbing action of a bee’s legs is a fundamental aspect of its personal hygiene, a behavior known as autogrooming. Bees use their legs as specialized cleaning tools to maintain the function of their sensory organs and keep their bodies free of debris. Their legs are equipped with various combs and brushes made of dense hairs designed for specific cleaning tasks.
The forelegs possess a specialized notch and comb structure at the joint, which acts as an antennae cleaner. The bee draws its antenna through this notch, using the comb to strip away dust, fine pollen, and other particles that interfere with its ability to smell and navigate. Clean antennae are necessary for communicating, locating food, and sensing pheromones within the hive.
The middle and hind legs are used to sweep the fuzzy surface of the bee’s body, wings, and abdomen, removing airborne contaminants and microscopic pests, like Varroa mites. Keeping the body clean is necessary for efficient flight, as even small amounts of dirt or pollen can disrupt aerodynamics. This diligent self-cleaning prevents the introduction of disease and parasites into the close quarters of the colony.