The Bee Proboscis: How Bees Drink Nectar

The mouthparts of a honey bee are one of those biological structures that look simple until you watch them in slow motion, at which point they become genuinely weird.

The bee lands on a flower. She unfolds her proboscis - a multi-part apparatus that, when fully extended, reaches about 6.5 millimeters in length (longer in some races; the Caucasian bee, Apis mellifera caucasica, has the longest proboscis among European subspecies, at roughly 7.2 millimeters). The proboscis slides into the flower's nectary. The bee feeds for 1 to 3 seconds. She retracts the proboscis. She flies to the next flower. She does this hundreds of times a day, visiting 50 to 1,000 flowers per foraging trip, collecting 25 to 40 milligrams of nectar per load.

The machinery that accomplishes this is not a straw. It's not a pump. It's a hairy, oscillating tongue operating inside a tube, running at 13 cycles per second, trapping fluid through a mechanism that wasn't correctly described until 2026.

Not a Straw

The textbook description of bee feeding, taught for roughly a century, was capillary suction. The story went like this: the bee extends her proboscis into the nectar. The two galeae (paired blade-like structures from the maxillae) and the labial palps form a tube around the central glossa (tongue). Capillary action draws nectar up the tube. The pharyngeal pump in the head creates suction that pulls nectar through the tube and into the honey crop (a specialized storage stomach in the abdomen).

This description was plausible. It was tidy. Parts of it were correct (the pharyngeal pump is real, the honey crop is real, the tube formation is real). But the capillary suction model had a problem: it couldn't explain why bees fed at different rates on nectars of different viscosities in the way they actually did. The math didn't work.

In 2026, researchers at Tsinghua University in Beijing, led by Jiangshui Wu, used high-speed video cameras filming at 1,000 frames per second to watch what actually happens when a bee feeds. The footage showed something the capillary model hadn't predicted: the glossa moves. Rapidly. In and out. 13 times per second.

The bee doesn't hold her tongue still in the nectar and let capillary action do the work. She laps. The glossa extends into the nectar, the fine branching hairs along its surface (called filopodial hairs, roughly 300 of them) absorb nectar, the glossa retracts into the tube formed by the galeae and labial palps, the nectar is squeezed off the hairs by the tube walls, and the process repeats. Thirteen times per second. Each cycle captures a tiny volume of nectar - roughly 0.5 to 1 microliter.

The feeding mechanism is closer to a cat lapping water than to a person drinking through a straw. But even the cat analogy isn't quite right, because the cat uses inertia to fling a column of water upward and catches it with its mouth. The bee uses the hairs on her tongue as a physical trap, erecting them on the withdrawal stroke to maximize the volume captured per lap.

The Hairy Tongue

The glossa is the key structure. It's a long, slender, flexible organ - roughly 3 to 4 millimeters long when extended - covered in rings of fine, branching hairs called filopodial papillae. These hairs are not passive decorations. They're hydraulically controlled.

When the glossa extends into the nectar, the hairs lie flat against the tongue surface, streamlining the glossa for penetration into the liquid. When the glossa begins to retract, hemolymph (insect blood) pressure inside the glossa changes, causing the hairs to erect - standing out from the tongue surface like the bristles of a bottlebrush. The erected hairs trap nectar between them through surface tension and viscous adhesion. The retraction pulls this trapped nectar into the tube.

The volume of nectar captured per lap depends on the nectar's viscosity, and the relationship is counterintuitive. Thin nectar (low sugar concentration, low viscosity) is captured in smaller volumes per lap because it drains off the hairs faster during retraction. Thick nectar (high sugar concentration, high viscosity) is captured in larger volumes per lap because it clings to the hairs more tenaciously. But thick nectar also slows the lapping rate - the tongue moves more slowly through viscous fluid, so fewer cycles per second means fewer laps per feeding bout.

The result is a trade-off curve. Maximum energy intake rate - the amount of sugar captured per second of feeding - peaks at a nectar concentration of roughly 50 to 60 percent sugar by weight. Below that concentration, the nectar flows easily but contains less sugar per unit volume. Above that concentration, the nectar contains more sugar per unit volume but flows so slowly that the feeding rate drops.

This optimum - 50 to 60 percent sugar - is remarkably close to the nectar concentration produced by the majority of flowers that bees pollinate. The alignment isn't coincidental. It's 80 million years of coevolution: flowers that produced nectar at the concentration bees fed on most efficiently attracted more bee visits, received more pollination, and produced more seeds. Bees whose tongues worked best at the concentration most flowers produced gathered more nectar and had more reproductive success. The tongue shaped the flower. The flower shaped the tongue.

The Proboscis Assembly

The glossa is just one part of the complete proboscis - a multi-part assemblage that unfolds from beneath the head like a Swiss Army knife.

The labrum and mandibles form the upper and outer mouthparts. The mandibles - the jaws - are used for chewing wax, shaping comb, biting other bees during combat, and manipulating propolis. They're not involved in nectar feeding.

The maxillae provide the galeae - two elongated, blade-shaped structures that fold along either side of the glossa. When the proboscis is extended for feeding, the galeae interlock with the labial palps to form the food canal - a tube surrounding the glossa through which nectar travels toward the head.

The labium provides the central structure: the prementum (the base), the labial palps (two segmented structures that form part of the food canal), and the glossa itself (the tongue, with its hairy surface and lapping motion).

The cibarium and pharynx are internal structures in the head that form the pharyngeal pump - a muscular chamber that creates suction to draw nectar from the food canal into the esophagus and eventually into the honey crop.

The entire assembly folds and unfolds in fractions of a second. A bee approaching a flower extends the proboscis during the final milliseconds of approach - sometimes before she's even landed. The extension is triggered by the detection of floral scent or visual floral cues, processed through the antennal and visual systems. The tongue is already out before the bee touches the flower.

The Honey Crop

The nectar collected by the proboscis goes into the honey crop - a expandable storage organ in the abdomen that can hold roughly 40 milligrams of nectar (about 40 microliters - roughly a large drop). The honey crop is separated from the true stomach (the ventriculus, where the bee digests food for her own metabolism) by the proventriculus, a muscular valve that controls flow between the two chambers.

The proventriculus allows the bee to keep nectar in the crop for transport back to the hive without digesting it. When the forager returns to the hive, she regurgitates the nectar from her crop into the mouth of a house bee, who processes it further - adding enzymes, evaporating water, and eventually depositing the concentrated solution into a comb cell for ripening into honey.

A forager making a typical trip visits 50 to 1,000 flowers, spending 1 to 3 seconds per flower, gradually filling her crop. The trip takes 30 to 60 minutes. The filled crop adds roughly 40 percent to her body weight, changing her flight dynamics significantly on the return trip. She flies heavier and slower, burning more fuel, which reduces the net nectar delivered to the hive. At extreme foraging distances (beyond about 5 kilometers), the fuel burned during the return flight approaches the energy content of the nectar carried, making the trip unprofitable.

The Water Drinker

The same proboscis that collects nectar also collects water, but the fluid dynamics are different. Water has a viscosity of roughly 1 centipoise. Nectar at 50 percent sugar has a viscosity of roughly 15 centipoise. The lapping mechanism works differently at different viscosities - the tongue moves faster in water (lower viscous resistance), but each lap captures less volume (water drains off the hairs faster).

Water collection is critical for thermoregulation - the colony evaporates water inside the hive to cool the brood nest on hot days. Water foragers use the same proboscis and crop as nectar foragers, but the internal plumbing routes differently: water destined for evaporative cooling is distributed to house bees who spread it on comb surfaces and fan it with their wings.

The proboscis of a water forager shows measurably higher wear than that of a nectar forager collecting from the same number of flowers, because water collection often occurs from rough surfaces (puddles, damp soil, swimming pool edges) rather than the smooth nectaries of flowers. The constant contact with abrasive surfaces wears the delicate hairs on the glossa.

Proboscis Length and Flower Access

The length of a bee's proboscis determines which flowers she can access. A honey bee with a 6.5-millimeter proboscis can reach nectaries up to roughly 6 millimeters deep. Flowers with deeper nectaries - certain species of clover, some salvias, many orchids - are inaccessible to short-tongued bees.

This creates ecological niche partitioning. Bumblebees, with proboscis lengths of 8 to 20 millimeters depending on species, access deeper flowers than honey bees can reach. Honey bees dominate on shallow-nectaried flowers (clovers, basswood, many fruit tree blossoms) where their colonial foraging efficiency - thousands of foragers from a single colony directed by the waggle dance - overwhelms the competition.

Within honey bee subspecies, proboscis length varies enough to matter. The Caucasian bee (A. m. caucasica) has a proboscis roughly 0.5 to 1 millimeter longer than the Italian bee (A. m. ligustica). This gives the Caucasian bee access to red clover - a flower whose nectary is too deep for most Italian bees. In regions where red clover is a major honey source, Caucasian genetics have been historically favored for this reason.

Breeding programs that focus on disease resistance sometimes overlook proboscis length as a selection criterion. But for colonies whose forage base includes deep-nectaried flowers, tongue length can be the difference between a 60-pound honey crop and a 90-pound one.

The Taste System

The proboscis isn't just a feeding tool - it's a sensory organ. The tip of the glossa contains taste receptors (gustatory sensilla) that allow the bee to assess the sugar concentration and composition of nectar before committing to feed. Additional taste receptors are located on the tarsi (feet) - a bee that steps on a sugar solution extends her proboscis reflexively, a response called the proboscis extension reflex (PER).

The PER is one of the most studied behaviors in neuroscience, because it provides a simple, reliable assay for associative learning. A bee is presented with an odor (the conditioned stimulus), followed by a sugar reward to the antenna or foot (the unconditioned stimulus). After one or a few pairings, the bee extends her proboscis in response to the odor alone - she's learned that the odor predicts food. The PER has been used to study learning, memory, olfactory processing, the effects of pesticides on cognition, and the neural basis of decision-making in insects.

The taste system is sensitive enough to distinguish not just sugar concentrations but sugar types. Bees prefer sucrose over glucose and glucose over fructose at equal concentrations. Natural nectars contain varying ratios of these sugars, and bees discriminate between them - preferentially visiting flowers with higher sucrose ratios when given a choice. This preference is detected at the proboscis tip in real time, during feeding, allowing the bee to make flower-by-flower decisions about whether the nectar quality justifies the time spent.

13 Laps Per Second

The glossa of a honey bee extends and retracts 13 times per second during active feeding. At each cycle, roughly 0.5 to 1 microliter of nectar is trapped by 300 hairs on a tongue 3 millimeters long. The nectar travels up a tube 6.5 millimeters long, driven by lapping motion and pharyngeal suction, into a crop that holds 40 microliters. The crop is filled in 1 to 3 minutes of active feeding, spread across 50 to 1,000 individual flower visits.

The total nectar volume a single bee collects in her 2 to 3-week foraging career - roughly 10 trips per day for 15 days at 40 microliters per trip - is about 6 milliliters. Six milliliters. About a teaspoon. Collected one tongue-lap at a time, 13 laps per second, from flowers that evolved to match the tongue that evolved to match the flowers.

A teaspoon of nectar becomes about half a teaspoon of honey after the water is evaporated. One bee, one career, half a teaspoon. A colony produces 60 pounds of honey in a good year because 20,000 foragers are each contributing their half-teaspoon, tongue-lap by tongue-lap, 13 cycles per second, for as long as the flowers bloom and the wings hold together.

The proboscis folds back under the head. The bee flies. She finds another flower. The tongue comes out. Thirteen laps. Retract. Fly. Repeat. A hundred times an hour, a thousand times a day, until the forager doesn't come home - and another bee, 21 days old, takes her first orientation flight, learns the landscape, finds a flower, and extends her tongue for the first time.

Same mechanism. Same 13 laps per second. Same hairy straw that isn't a straw, feeding on flowers that are expecting her.