Bumble bees tongues (proboscis) fall into 2, sometimes 3 different categories depending on their length. As the name implies, long-tongued bees have a much longer proboscis than short-tongued bees. According to research, this is significant. Not only does it determine the manner in which bees feed and what they feed. It also has an environmental and ecological impact.
Bees are incredibly efficient pollinators, collecting the necessary pollen from flowers to fertilize other plants sharing the same species. To do this, a bee must extend its proboscis, deep within the flower’s corolla to lap up the nectar inside. Generally, its tongue is protected by a long sheath of two parts. The first part is the beak, which folds under the bee’s body when it flies, and the second part is the maxilla, which allows the bee to unfold its tongue and reach into a flower.
Despite their efficiency and specialization however, long-tongued bees must be careful not to rely too much on a single kind of flower or risk losing important territory to hardier, short-tongued bees from other parts of the world. This has been seen in Argentina, where a native long-tongued bee species lost ground to an imported short-tongued bee that had been brought in to help pollinate tomatoes.
Construction of the Bumble Bee Tongue
Bees have developed specialized, interlocking mouthparts that move to gain access to hard-to-reach floral rewards. This complex system of moving pieces allows bees to lap up nectar, suck up liquids, and reach into crevices of flowers.
The tongue of bumble bees is similar to that of other bees. It features a complex combination of elements that enable the bee to feed efficiently. At the tip, there is a lapping capillary structure that allows them to draw liquid into the mouth. Further down the length of the tongue is a suctorial tube which acts as a straw, allowing the bee to suck up more liquid.
Bumble bee tongues are unique in their construction and proportions when compared to other insect species. The lapping capillary at the tip is larger and longer than those found on most bees while the suctorial tube that follows it is shorter. This design allows them to feed quickly and efficiently on nectar, allowing them to move between flowers in search of food.
Parts of the Tongue
The true tongue is a flexible tube (glossa or salivary canal) located in the center of the oral cavity. The glossa lends the tongue it strength and stability. The proboscis, (typically referred to as the tongue) is supple and hairy to lap up nectar.
The densly haired labellum, located at the tip of the hairy glossa, is a vital tool for bees to gather food. Shaped like a tiny hairy bowl, the bee uses it to collect nectar from deep within a flower. The dense hair is to avoid spillages.
The proboscis of a long-tongued bee is an incredibly complex structure consisting of two inner and four outer components. Extending from the tip of the glossa are two tubes called labial palpi. These fit precisely against the walls of the galeae and form an incredibly tight seal. The galeae are two sheaths that surround the labial palpi and the glossa. They are held firmly in place by tiny spines along their inner walls.
In essence, the one-part glossa is encapsulated within a four-part tube, allowing the bee to safely transport liquid nectar from its mouthparts to its stomach.
The other parts include the (Lorum, mentum, and prementum), as well as the Cardo, stepes, and maxillary that allow the extending mouthparts to move outward.
Mechanics – How the Tongue Works
They ingest liquid food through a process called viscous dipping. This involves the bee extending its tongue and immersing it into nectar, trapping it in the process. As they do so, hairs on their tongue are erect asynchronously. This further improves their ability to capture the nectar. The tongue is then retracted, forming a tube from the galeae and labial palpi. Finally, the nectar is sucked into the pharynx. To make this process easier, ridges on the inner wall of galeae reduce friction during ingestion.
Short Tongued Bees
Short tongued bees are generally found in four major families. These include the cosmopolitan solitary, ground-nesting family of Andrenidae that has an enormous genera of around 2,000 species, the Halictidae, which is the 2nd largest family of bees with almost 4,500 species. Bees of the Colletidae family, often referred to collectively as plasterer bees, and the small Melittidae family of around 200+ species also belong to the group of short tongued bees. They include mining bees (Andrena), plasterer bees (Colletes) and yellow-face bees (Hylaeus), end-banded furrow bees (Halictus) and base-banded furrow bees (Lassioglossum), pantaloon bees (Dasypoda), oil-collecting bees (Macropis) and blunthorn bees (Melitta).
Short tongued bees are bees with a length of tongue up to half the length of their head, and typically feed on nectar found in shallow-throated flowers.
Nectar-robbing is a foraging technique employed by certain species of short-tongued bees. These bees lack the ability to visit flowers with long tubes in the traditional manner. They learnt to chew a hole near the base of the flower through which they extract the nectar instead of using their tongue. This can damage the flower, leaving them exposed to predators. In addition, it reduces their success to reproduce because the bees often fail to collect pollen this way.
Bombus occidentalis have mandibles that are notably more toothed than those of other bumble species. This allows them to cut into the flowers they visit. This is a key adaptation that makes them specialized flower-visitors, as it allows them to bypass the process of manipulating the petals of a flower to access the nectar within. The mandibles are unilateral, curved and serrated, creating saw-like edges along the cutting surfaces.
Medium Tongued Bees
Medium-tongued bees include Melitta, Dasypoda, Halictus, and Lasioglossum species, with a length of about 3.5–5.5 mm.
Long tongued Bees
Out of the seven bee families that exist worldwide, only two are considered long-tongued: the Apidae and Megachilidae. The Apidae family is made up of honeybees, bumblebees and stingless bees.
The Megachilidae family has over 4,000 species worldwide, with an estimated 630 species in North America alone and represents 15% to 20% of named bee species. They include mason bees (Osmia), leafcutter bees (Megachile) and resin bees (Heriades), and carder or potter bees (Anthidium),
The Apidae family counts over 5700 species of bees. The family includes some of the most commonly seen bees, including bumble bees (Bombus), honey bees (Apis mellifera), stingless bees, carpenter bees, orchid bees, cuckoo bees.
Long tongued bees proboscis have a length of more than half the length of their head. This makes them well-suited for visiting deeper flowers and collecting nectar from farther depths. This is especially useful for flowers that have narrow and deep throats, such as lilies or narcissus, where short-tongued bees would not be able to reach.
These bees are essential pollinators of many plants, and their unique adaptations allow them to feed on the nectar and pollen found within deep recesses of flowers.