When a bee lands on a flower, the apparatus it extends to drink nectar is often called a tongue, but the technical term for this mouthpart is the proboscis. This specialized appendage is a temporary, jointed structure used to ingest all necessary liquids, including water, honey, and nectar from flowers. Its design allows the bee to access liquid resources from a diverse range of floral shapes and depths. Without the proboscis, the bee would be unable to sustain itself or contribute to the colony’s food stores.
The Bee’s Feeding Apparatus: The Proboscis
The proboscis is a collection of distinct mouthparts that temporarily lock together to form a functional feeding tube. The central element is the glossa, which is the true tongue-like structure. The glossa is elongated, flexible, and covered in thousands of fine, transverse hairs.
Other components are derived from the insect’s maxillae and labium. The maxillae contribute the galea, and the labium provides the labial palpi. These four structures—the two galeae and the two labial palpi—encase the glossa. When extended, this combination creates a straw-like tube called the food canal, enabling the bee to draw liquids upward.
The Mechanics of Nectar Collection
The bee’s method of drinking involves two distinct actions: lapping and sucking. The mechanism used depends on the liquid’s viscosity and depth within the flower. For thicker, syrupy nectars, the bee primarily uses a lapping motion.
In lapping, the hairy glossa is rapidly dipped into and retracted from the liquid. Thousands of tiny bristles covering the glossa trap the nectar through capillary action. As the glossa is pulled back, the liquid is stripped off and moved toward the mouth opening.
For less viscous liquids, such as water or thin nectar, the bee switches to a direct suction mechanism. In this mode, the proboscis remains submerged. A muscular pump inside the bee’s head creates negative pressure, drawing the liquid up through the food canal. This ability to switch methods allows the bee to extract nectar efficiently from various floral resources.
Tongue Length and Foraging Specialization
The physical length of the proboscis is a factor that determines a bee species’ foraging behavior and resource preference. Bees are categorized into long-tongued and short-tongued groups. Long-tongued bees, such as the garden bumblebee, can have a proboscis up to 15 millimeters, enabling them to reach nectar at the bottom of deep, tubular flowers like honeysuckle or red clover.
Short-tongued species, including most honeybees, have a shorter reach. These bees are restricted to flowers with shallow or easily accessible nectar sources. If a short-tongued bee encounters a deep flower, it may resort to nectar robbing.
Nectar robbing involves using the mandibles to bite a hole through the side or base of the flower corolla. This action allows the bee to bypass the natural opening and steal the nectar without contacting the pollen-bearing anthers.
Storage and Maintenance of the Proboscis
When the bee is not actively feeding, the proboscis is fully retracted and folded. The various parts, including the glossa, maxillae, and labial palpi, collapse and tuck away beneath the head and mandibles. This compact arrangement protects the feeding mechanism from damage during flight.
Maintaining the cleanliness of the proboscis is part of the bee’s hygiene routine. Pollen and other contaminants can cling to the fine hairs on the glossa during foraging. The bee frequently performs grooming behavior, using its legs to clean the entire feeding apparatus and ensure it remains functional.