Tiny but Mighty: The Incredible Physics of Bees 

Tzu-Yu Hung, Alysha Kutuzyan, Katarina Simanic, Steven Yang

Abstract

This article explores the various physical phenomena with respect to bees and their colonies, including flying and navigation techniques, sensing and communication methods, as well as thermoregulation and defence mechanisms. The flight strategy of bees characterizes by a low-amplitude high-frequency stroke pattern and unsteady aerodynamic mechanisms. Bees can navigate and forage through the wild with magnetoreception, electroreception and skylight polarization patterns. On the other hand, bees can form stable clusters and colonies. Foraging bees perform bee dances and generate electric fields to communicate with each other. Both individual and collective thermoregulation of bees and their defence mechanisms reveal fascinating physical aspects of bees’ behaviours. With all these underlying physical phenomena, ranging from aerodynamics, electroreception to thermodynamics, bees are indeed mighty superorganisms despite their tiny body. 

Introduction

Bees, being a widely known and omnipresent insect species to humans (in part by their semi-domestication), are often overlooked by the average person. Apart from the understanding that they produce honey in their colonial hives, many are unaware of bee superpowers that led them to thrive across the globe — with the help of humans or independently in the wild. These tiny, fuzzy, eusocial Hymenoptera continue to surprise scientists after decades of research (Fig. 1). For example, bee flight was once concluded to be aerodynamically “impossible” due to prejudice about their short and stubby bodies. Yet, nature has rendered this possible, and bee flight mechanisms are now understood with increased knowledge in aerodynamics (Altshuler et al., 2005). Bees use this ability to fly many miles to harvest nectar but always find the shortest path back home (Heinze, 2013). Their incredible navigational awareness stems from their propensity to visual landmark cues, recognition of skylight polarization patterns, and magnetoreceptive senses (Liang et al., 2016). Researchers are also fascinated by the logistics of their “hive mind” that lets them band together to effectively gather resources, raise their colony, and defend their nest. The worker bee’s cute waggle dance serves as a precise means of directing fellow foragers to resource hubs via its manipulation of airstreams and electric fields (Greggers et al., 2013). By efficiently grouping themselves, bees can also use their individual flight, heat emitting, and other anatomical capabilities to form physically and thermally stable clusters, cool down their hive, and defend their colony (Peters et al., 2022; Seeley, 2019). Learning about these bee superpowers inspires engineers to mimic how bees harness the laws of physics to stay mighty despite their tiny size. 

Fig. 1 Worker bee collecting nectar and pollen on a goldenrod (Solidago sp.) inflorescence. (Seeley, 2019) 

Individual Bee Flight Paradox 

In 1934, August Magnan from mathematical calculations and all known laws of aviation that bees cannot generate enough lift to fly due to their relatively small wing size and seemingly haphazard flapping of their (Magnan, 1934). This is obviously contrary to the reality. Fortunately, in 2005, with an increased understanding of aerodynamic theory and high-speed digital photography, Michael H. Dickinson and his colleagues figured out the secret of bee flight. 

Dickinson pointed out that the conventional fixed-wing aerodynamic theory used by Magnan was insufficient to explain bee flight (Altshuler et al., 2005). Instead, during insect flight, flapping involves rapid rotation of wings around their base and the aerodynamic generated during each wing stroke keep them in the air (Dickinson et al., 1999). 

The presence of high-magnitude force transients at stroke reversal suggests the use of unsteady mechanisms in bee-hovering (Altshuler et al., 2005). At stroke transition between upstroke and downstroke, the wings rapidly rotate and reverse direction, as illustrated in Fig. 2. Besides the additional vortices and upward forces produced by the wing’s rotational circulation, added mass effect is one key component of the unsteady forces generated (Altshuler et al., 2005). When the wing accelerates during stroke reversal, it experiences pressure force from the surrounding air as additional wing mass and the added inertia further contributes to acceleration of the wing (Chin & Lentink, 2016). Another significant part of the unsteady aerodynamic effect is wake capture (Altshuler et al., 2005). Immediately following stroke reversal, the wing can “capture” the shed vorticity from its previous stroke (Dickinson et al., 1999) and this helps explain the force peaks at the start of each half stroke, as shown in Fig. 3. 

Fig. 2 Wing kinematics during a flapping cycle. The diagram illustrates a flapping motion consisting of downstroke (t = 0 – 0.5) and upstroke (t= 0.5 – 1), connected by wing rotations at each stroke transition. “t“ is nondimensional time. (Shah et al., 2023) 

Fig. 3 The aerodynamics of honeybee hovering. The data presents lift (black trace) and (green trace) forces produced by the left wing for one individual during four wingbeats with the downstroke shaded in grey. Forces produced by the right wing were qualitatively similar. (Altshuler et al., 2005) Forces have been scaled to honeybee dimensions (Fry et al., 2005). 

Bee flight mechanism is also characterized by a relatively low-amplitude and high-frequency stroke pattern (Altshuler et al., 2005). Most insects, including Drosophila, demonstrate wingbeats with large stroke amplitudes to generate enough lift, typically in an arc between 145° and 165°, as illustrated in Fig. 4 (Fry et al., 2005). However, bees, with an average wing length of 9.7 mm, hover with relatively low stroke amplitude of around 90° separated by rapid reversals (Altshuler et al., 2005) and to compensate, the wings beat at around 240 Hz (Sotavalta, 1952), almost equivalent to the A3 string of cello at 220 Hz. This is relatively high compared to Drosophila, which flaps its 2.5 mm wings only at 200 Hz (Altshuler et al., 2005). Interestingly, in contrast to insects with large stroke amplitude, where translational forces dominate those generated during stroke reversal (Fry et al., 2005), added mass effect contributes relatively greater to aerodynamic forces at shorter amplitude strokes (Altshuler et al., 2005), suggesting that acceleration-reaction is indeed a significant component of the unsteady mechanisms of bee flight. 

Fig. 4 Wing position in body centered polar coordinates. Wing position is defined by three angles: (1) stroke position, of which the span corresponds to stroke amplitude, (2) stroke deviation, and (3) angle of attack, which measures the rotation around wingspan (Fry et al., 2005). 

Bee Flight Manipulation 

Bees forage in highly complex and unsteady natural environments, adapting their flight strategies to navigate these challenging conditions Bees routinely carry pollen and nectar loads representing 20% and 35% of their body mass respectively and studies have reported that occasionally, foragers can carry (Winston, 1991). To carry heavy loads during flight, bees must increase their aerodynamic force output. Insects with large stroke amplitude rely more on the forces produced from the wing translational phases (Fry et al., 2005), while those with small stroke amplitude generate significant forces primarily during wing rotation (Glass et al., 2024). Bees, with an amplitude of around 90°, lie in the middle of this range and rely on both translational and rotational phases to generate sufficient forces (Glass et al., 2024). Based on the knowledge that aerodynamic forces decline with air density, researchers challenged bees to fly in heliox, a breathing gas mixture of helium and oxygen. More specifically, normoxic heliox that contains a mixture of 21% oxygen (the same amount as in normal air) and 79% helium is used to create conditions requiring bees to exert more effort to remain airborne, since normoxic heliox has a much lower air density than ambient air (Altshuler et al., 2005). Results showed that in heliox, bees manipulate their stroke pattern by maintaining nearly constant wingbeat frequency but increasing stroke amplitude by nearly 50%, to an average value of 132° (Altshuler et al., 2005), presumably increasing relative contribution of translational forces. This can partly be explained by minimizing the increase in wingbeat frequency since that contributes substantially to metabolic costs (Glass et al., 2024). However, as bees rely on both translational and rotational forces, manipulation in the latter at each stroke reversal may also be involved. 

Combined laboratory and field experiments observed that bees do not avoid foraging in windy conditions (Crall et al., 2017). To sustain flight, they use a series of active responses to overcome higher wind speeds and turbulence intensities. 

Bees have shown higher mean wingbeat frequency and stroke amplitude in turbulence (Crall et al., 2017). This change in frequency may cost more energy but it is necessary for increasing control authority, by minimizing the time between each stroke and thus reducing the delay in updating control input to wing kinematics (Ristroph et al., 2013). Whereas an increase in amplitude, similar to the manipulation during load-carrying, suggests a potential demand for higher aerodynamic power output (Altshuler et al., 2005). 

In addition to stroke pattern change, bees also demonstrate a body rolling mechanism in unsteady wakes. To resist perturbations and maintain stability, active abdominal deflection was observed during lateral maneuvers, whether voluntary or corrective, thereby correcting for the disturbance through inertial reorientation (roll) (Ravi et al., 2013). In fact, bees displayed more variable and extreme wing kinetics, and increased left-right asymmetry in stroke amplitude during turbulence (Crall et al., 2017). This is significantly correlated with the roll angle of the body, suggesting that bees employ asymmetric stroke amplitude to generate both asymmetric lift and drag in wings to help control body orientation, thereby generating a net torque (Crall et al., 2017). 

Morphological Implication in Bee Flight 

Despite the small wing size, nature has shown the fascinating flying ability of bees. In addition to their short-amplitude high-frequency wing stroke pattern, scientists observed certain morphological significances of this naturally efficient flying system. 

One interesting feature of insect wings is vein corrugation, which refers to complex vein structures that form irregular, three-dimensional patterns on the wing surfaces (Shah et al., 2023). Flow analysis and comparison between smooth and corrugated bee wing models revealed that vein corrugation significantly enhanced lift by 14% (Shah et al., 2023). Leading edge vortex (LEV) is generated by the leading edge of wings moving at high angels of attack (Chin & Lentink, 2016). Corrugation extends the region of negative pressure, traps a portion of the vortices on the wing surface, and stretches the LEV downstream toward the wake, as shown in Fig. 5 (Shah et al., 2023). In this way, corrugation increases the size and of LEV and thereby, enhancing the overall lift. 

Fig. 5 Spanwise Z-vorticity showing LEV for (a) corrugated and (b) smooth wing models. At 2.5 m/s during downstroke (t = 0.31), as LEV develops at 75%, corrugation trips the flow, trapping vortices between 12.5% to 50% and stretching a portion of LEV toward the wake, whereas only a single coherent LEV forms along the smooth wing surface (Shah et al., 2023). 

Scientists also point out the importance of forewing and hindwing coupling mechanism in bee flight. The hamulate coupling structure creates a stable but still flexible connection between the two wings, allowing them to rotate with respect to each other. Although forewing generates the main power for flight, hindwing is essential in that it mechanically synchronises with the forewing and provide an additional area for lift generation (Ma et al., 2019). More specifically, simulations with corrugated bee wing models show that lift increases from 14% to 38% as speed rises when the hindwing is included. This improvement stems from the camber created at the forewing, which generates recirculation zones and lowers pressure to boost lift on the hindwing (Shah et al., 2023).  

An Optical Perspective on Bees 

Whether recognizing flowers or spotting fast-moving landmarks during flight, the foraging behaviors of bees relies on their ability to interpret visual cues (Warrant, 2019). To accommodate these needs, bees use two optical systems: three ocelli, arranged triangularly in the head’s center, and two compound eyes, positioned laterally on either side (Fig. 6) (Klowden & Palli, 2023).  

Fig. 6 A frontal view of the male drone honeybee’s five distinct eyes, consisting of lateral ocelli (Io), median ocelli (mo), and the compound eyes (ce). A closer look at the compound eyes reveals thousands of ommatidia lenses. (Ribi et al., 2011) 

Although simple in structure, ocelli eyes provide bees with rapid but rudimentary information (Klowden & Palli, 2023). They consist of a convex lens which directs incoming light onto a surface of light-sensitive retinula cells, which convert light into electrical signals. The focal planes of lateral ocelli eyes are behind the retina, indicating their images are blurred (Ribi et al., 2011). However, the low focal-length to lens-diameter ratio of ocelli eyes renders them particularly sensitive to light. Ocelli eyes also transmit visual information considerably faster than compound eyes, in 6 – 9.5 ms (Ribi et al., 2011). As a result, ocelli eyes assist with flight stabilization; however, they yield no detailed information about the bee’s (Ribi et al., 2011).  

It is therefore up to compound eyes (Fig. 7) to generate a more elaborate, colorful, and motion-sensitive picture. Compound eyes are characteristic of arthropods and differ significantly from the camera eye system of land vertebrates, which uses a single large lens to focus a single image on the retina (Klowden & Palli, 2023). Instead, insect compound eyes are divided into hundreds, even thousands, of miniature optical units called ommatidia (Klowden & Palli, 2023). Each ommatidia is a self-contained system which receives only a narrow beam of light. Incident photons entering the ommatidia will first pass through a lens and a crystalline cone, which focus the ray perpendicularly onto a layer of microvilli. It is within the microvilli that the light arrives at the key photoreceptive protein, rhodopsin, which absorbs and transduces light energy into electrical signals headed to the brain. Bee neural networks integrate data from approximately 5500 ommatidia to construct a single image of their surroundings. Since this system uses lenses with smaller diameters – often ranging from 20-110x larger than the wavelengths of visible light (Warrant, 2019) – incident light is diffracted more in compound eyes than camera eyes, resulting in a lower image resolution (Land, 2009).

Fig. 7 Structure of an apposition compound eye. Light that enters through the cornea and crystalline cone is traduced within receptor cells and then transmitted as action potentials by receptor axons. (Land, 2009).  

Navigation by Skylight Polarization Patterns 

While away from the hive, bees continuously keep track of their orientation and distance traveled with such accuracy that they return home on a short and straight path (Heinze, 2013). Such an impressive feat requires a precise set of navigational tools. One of the bee’s primary strategies is to orient itself based on patterns of polarized sunlight (Menzel & Snyder, 1974).  

Light is an electromagnetic wave with electric and magnetic fields oscillating perpendicular to each other and the direction of propagation. It comes in two forms: unpolarized light, in which the field oscillations are random and along multiple planes, and polarized light, in which the field oscillations occur along a single plane. Initially, light emitted from the sun is unpolarized; however, when it passes through Earth’s , it encounters particles small enough to scatter it at varying angles. The process is called Rayleigh scattering, and it polarizes light differently based on the scattering angle (Goldstein, 2017). For example, light scattered at a 90° angle will be completely linearly polarized, whereas light which does not change direction will not be polarized at all. At an angle between these two extremes, light will be partially polarized. As the position of the sun changes throughout the day, this phenomenon produces skylight polarization patterns which rotate around a single northern point (Fig. 8).  

Fig. 8 Sunlight polarization patterns, resulting from Rayleigh scattering, change as a function of the sun’s elevation. (Heinze, 2013) 

It turns out that the photosensitive protein of bee eyes, rhodopsin, is more absorptive when the electric field oscillations of light align with its bonds (Menzel & Snyder, 1974). Bee physiology takes advantage of this property by arranging bundles of rhodopsin-rich microvilli orthogonally within ommatidia, enabling light absorption to be measured along two axes. Light absorbance can thus be used as a proxy for light polarization along either plane. This mechanism allows bees to “see” sky polarization patterns and calibrate their internal compass accordingly. Impressively, this navigational tool is reliable even under conditions where the sky is almost completely obscured by a cloud overcast or foliage, as it only requires access to a small patch of sunlight (Kraft et al., 2011).  

Navigation by Magnetoreception 

When placed within a controlled magnetic environment, research has demonstrated that bees can be taught to use magnetic fields as navigational maps to find sucrose rewards (Lambinet et al., 2017). Similarly, bee foraging behaviors can be disrupted by placing a magnet on the bee (Klowden & Palli, 2023). The prevailing explanation for these behaviors is that bee navigation involves magnetite-based magnetoreception. Tiny iron granules embedded within fat cells of the bee abdomen are believed to act as magnetic sensors which, in the presence of a magnetic field, rearrange themselves according to the direction that the magnetic field flows (Fig. 9) (Liang et al., 2016). This occurs because iron is a ferromagnetic material; iron atoms possess atomic magnetic moments due to the spin of their electrons (Dalven, 1990). These atomic magnetic moments can align parallelly to produce overall magnetic poles on the iron granule. Models for magnetoreception suggest that magnetic field data is then gathered as an average over time (England & Robert, 2022).  

Fig. 9 Iron granules in the abdomen of Honeybees, as viewed under a microscope. (a) Black magnetic granules, indicated by black arrowheads, in the belly of a live honeybee. (b) Magnetic granules in abdomen of live honeybee under an applied magnetic field of 1 Gauss, indicated by the white arrow. (Hsu et al., 2007) 

It is believed that the magnetic interactions between bees, their swarm, and their ecological environment are too weak and too brief for magnetoreception to be of use (England & Robert, 2022). However, the Earth’s geomagnetic field, which flows consistently from the southern to northern hemisphere, presents a natural azimuth for bees to exploit (Lambinet et al., 2017). The geomagnetic south pole will apply an attractive force on the iron granule’s north pole, and vice versa, causes the iron granule to reorient itself similarly to the needle of a compass. Bees may use this mechanism of magnetoreception to interpret the geomagnetic field, helping them navigate during foraging and arrange their honeycomb structures (Lambinet et al., 2017). 

The Bee Dance

The honeybee dance language is a fascinating method of communication that bees use to inform other hive members about the location of resources. Dr. Karl von Frisch was the first to experimentally study and decode the meaning behind the dance. He proposed that bees perform two different dances based on the distance to resources: the round dance and the waggle dance (Frisch, 1993). 

The waggle dance consists of a figure-eight movement pattern repeatedly performed by a bee (Visscher, 2009). It can be thought of as a reenactment of the flight path taken by the bee to get to the food source. The dancing bee moves in a straight-line path (the waggle run), then turns to the right or left and circles back (Fig. 10a) (Frisch, 1993). As the distance to the food source increases, so does the duration of the waggle run. During this run, the dancer vibrates their wings while emitting around 280 Hz sounds and moves their abdomen from side to side 13-15 times per second (Michelsen, 2014). To show direction, the waggle run is performed on the comb at an angle relative to the sun azimuth (Fig. 10b) (Visscher, 2009). During the round dance, the bee walks in a circle, then turns back and walks in the opposite direction (Fig. 10b). This behavior does not communicate any direction or distance, only that there is a food source nearby (Frisch, 1993). 

Fig. 10a Mechanisms of the bee dance. The path taken by the bee while performing the waggle and round dance. The waggle run occurs in the straight path portion of the dance, where the bee moves the abdomen from side to side (Visscher, 2009).  

Fig. 10b The direction in which the bee performs the waggle dance, with the angle relative to the sun’s azimuth (Frisch, 1993).

There is much speculation on how follower bees interpret the information given by a dancing bee. Dr. Karl von Frish initially suggested that follower bees either detected vibration in the combs or physically touched the dancer (Frisch, 1993). A third hypothesis, proposed in 1987, suggested that follower bees remain close behind the dancer and detect the path using airflow receptor organs (Michelsen et al., 1987). After measuring airflow around a robotic model, it was found that the airflow decreased as distance decreased (Michelsen et al., 1987). This led to the idea that airflows could be used to communicate distance and direction.  

Further research using particle image velocimetry (PIV) revealed discrepancies with this theory. It was found that the airflow is more complex than previously thought. When a bee moves their body, they displace air in the direction of movement and leave behind empty space (Michelsen, 2014). The air that comes in to fill this space flows from both the opposite side and back of the body, causing airflow collisions and the creation of eddies (Michelsen, 2014). This finding suggests that oscillating airflows from the body and wings do not provide sufficient information for communication. However, these PIV studies led to a new hypothesis: Not only do the oscillations of the wings create oscillating airflows, but they also generate jet airflows that move backward from the wings (Michelsen, 2014). This jet stream is more fan-shaped and flows in only one direction, compared to oscillating ones that have air flowing to and from (Fig. 11). There are two types of jet streams formed: narrow jets and broad jets (Michelsen, 2014).  

Fig. 11a PIV visualized simulated airflows. Airflow of a from a simulated bee wagging movement. Displaced air results in airflow collisions which in turn, causes eddies (e) to form.

Fig. 11b A jet airflow created by a 250-Hz wing vibration (Michelsen, 2014). 

The airflow patterns generated by the dancing bee change based on the follower’s location (Michelsen, 2014). This is why it is important for the follower bees to be in the correct position behind the dancing bee. When this is the case, they have a higher success in finding where the food source is located. 

Electric Field Generation 

Bees can accumulate an electric charge or fields through different movements such as flying, landing, walking, and dancing (Zakon, 2016). The fields they generate can change in frequency and can induce passive antenna movements in idle bees (Greggers et al., 2013). This is due to Coulombs Law, F = \frac{kq_1q_2}{r^2}, which calculates the force between two charged particles. Depending on the movement of the bee, its body can be surrounded by an electric field. As the wings and body parts rub against each other, the charge can refresh and thus, they can continuously emit an electric field (Greggers et al., 2013). 

It was found that the electric fields generated by bees are closely related to their body movements. When bees arrive at the entrance of the hive, they can carry a charge that can measure from 0-450 V (Greggers et al., 2013). When they land, the charge only dissipates by a small amount and remains high due to a decrease in humidity and charge accumulation due to movement within the hive.  

In addition to airflows, dancing bees can also generate an electric field. In a study performed by Greggers et al., the measurement of the waggle dance of 40 bees found their movements occurred at a frequency of 16.5 Hz and generated an average of 3-5 electric pulses (Fig. 12) (Greggers et al., 2013). The vibration of their wings, occurring at 230 Hz, created voltages of up to 200 V, and in turn generated an electric field (Fig. 12) (Greggers et al., 2013). 

Fig. 12 The electric field pattern produced by a dancing bee. (a,b) Provide a view of the indicated middle section of (c). The top two recording show (a) The low frequency components and (b) the high frequency components. The movements of the dancing bee led to a modulation of the electric field (Greggers et al., 2013).  

The electric fields generated by these dancing bees were also found to cause antenna vibrations. In a study that observed how the antenna vibrations differed with airflow and electric charge; it was seen that a charged wing led to a significantly higher vibration amplitude compared to airflow alone (Zakon, 2016). Along with the antenna, it was found that these weak electric fields also cause a response in the filiform hairs on the bee’s body. When exposed to the same applied electric fields, the hairs responded with a velocity an order of magnitude greater than that of the antennae (Zakon, 2016).  

Electric fields also play a role in how bees interpret the waggle dance. As the moving wings and abdomen move closer and farther away from the follower bee, it can sense the changes in amplitude of the electric field (Greggers et al., 2013). This was seen by observing antenna movement exhibited by the follower bee. 

Electroreception  

All around, there exists a complex network of electric fields and charges which are completely undetectable to us; however, a subset of species, including bees, can sense and interpret their electrical environments using a specialized ability called electroreception. Electroreception is believed to have initially emerged over 500 million years ago in aquatic species (Collin, 2010), and was first discovered in sharks, who use electric signals to detect and track their prey underwater (England & Robert, 2022). Aquatic electroreception relies on the fact that all living organisms contain electric charges. These charges come in the form of membrane potentials resulting from ion gradients, or action potentials in nervous system, and by Gauss’s law, they inherently generate an electric field. In conductive mediums such as , or even moistened soil, bioelectric fields can induce electric currents which nearby organisms can detect using receptors on their (England & Robert, 2022).  

However, this description of electroreception in wet environments, where electrical information is deciphered from current flow, seems to imply that electroreception would not be possible for an aerial organism such as a bee (England & Robert, 2022). Air, containing few charged particles, is an insulating medium; any electric current generated by one organism is unlikely to propagate far enough through air to be received by other organisms. However, current induction is not the only effect a charged object can exert on its surroundings. Coulomb’s law explains how electrically charged objects also exert forces on other charged objects. These electric forces occur even when the objects are separated, and in any medium. By harnessing this law, bees have adjusted electroreception for aerial use.  

The mechanisms underlying aerial electroreception are simple in concept. A charged electroreceptive organism, such as a bee, in the proximity of some other charged thing, such as a flower, will be acted upon by an electrical force (England & Robert, 2022). The force will induce the movement of a mechanosensory organ, which transduces the motion into an action potential. Mechanoreceptors vary by bee species; for example, bumblebee fur is understood to be their primary electroreceptor, as it undergoes the greatest deflections due to Coulomb’s force and stimulates the most neural activity (Sutton et al., 2016). By contrast, honeybees rely on the second segment of their antennae to detect and interpret electric fields. The sensitivity – and thus, the effectiveness – of either mechanoreceptor is directly proportional to the magnitude of charge the organism carries. Bees are particularly well-suited for the task of detecting electric forces given that they naturally accumulate a positive charge during flight, due to the friction from air resistance and wing flutters (England & Robert, 2022).  

Electroreception allows bees to coordinate foraging efforts within their colonies. For example, research suggests that bumblebees interpret electrical signals to identify which flowers have already been pollinated (England & Robert, 2022). When a bee visits a flower, its positive charge induces a temporary current in the plant which measurably alters the flower’s electric field for up to 100 s afterwards (England & Robert, 2022). This essentially marks the plant with the bee’s electrical footprint. Other bumblebees interpret these electrical flower clues to identify whether a flower has already been visited and redirect their efforts elsewhere. Meanwhile, honeybees use electroreception to interpret waggle dances, and efficiently communicate foraging information (England & Robert, 2022). 

Mechanisms of Honeybee Clusters 

When bee colonies relocate during colony fission, most of the workers and the queen leave the hive and move to a nearby tree branch. On this branch, around 10 000 bees come together and form a cluster-like hanging structure (Fig. 13a) (Peters et al., 2022). Usually, the cluster forms a pendant structure; however, the shape can vary depending on the surface to which they are attached (Peleg et al., 2018). This structure keeps its form for multiple days while scouter bees look for a new home (Peters et al., 2022). During this stage of relocation, the bees are exposed to the environment, and depending on the mechanical and thermal conditions, they exhibit different types of behavior. The cluster is forced to adapt to these influences, including applied dynamic loads with varying properties such as amplitude, orientation, duration, and frequency. 

When exposed to weak horizontal forces, it was found that the cluster shakes side-to-side at a frequency of around 1 Hz (Peleg et al., 2018). Once the force reaches a certain threshold, the structure starts to flatten as the bees adapt by spreading out to increase their attachment area. This continues as the duration, frequency, and acceleration increase (Fig. 13b,c) (Peleg et al., 2018). 

Fig. 13 Findings from a study that tested how clusters adapt to horizontal forces. (a) A cluster of bees on a tree branch. (b) An experimental set up with a bee cluster on a wooden board. (c) The top panel shows the acceleration versus time of this wooden board. The bottom two panels show how the bee clusters adapt to horizontal forces over time (Peleg et al., 2018). 

Individual bees can sense areas within the cluster that have become deformed and instinctively move from regions of higher displacement to areas with lower displacement (Peleg et al., 2018). This leads to an overall more stable structure. When the shaking stops, the cluster returns to its original form. When exposed to vertical winds and forces, the bee clusters do not react in the same way. They do not adapt and keep relatively the same structure (Peleg et al., 2018).  

An Organization of Thermoregulation 

Honeybee larvae are susceptible to thermal deviations. Indeed, brood incubated in temperatures that slightly deviated from the optimal 34.5-35.5°C had clear behaviour issues as adults (less precise waggle dances) due to brain malformations (less neural connections). Even well incubated adult bees remain vulnerable to temperature fluctuations. At 8°C, they enter a frost coma (dying within 48 hours); at 18°C, they cannot activate their flight muscles (to heat themselves); and they can only survive a few hours when over 45°C (without mentioning that beeswax softens dangerously at 40°C). It is therefore unsurprising that bees, being an originally tropical species, have developed adaptations to thrive in diverse climates globally (including Quebec’s harsh winters) by manipulating the mechanisms of thermal conduction, convection, and radiation (Seeley, 2019). 

Warming up 

A bee’s heating mechanism is evolutionarily derived from its flight adaptations. Flight is one of the most energy-demanding activities in the animal kingdom, and bees are no exception. A worker bee expends approximately 500 watts per kilogram during flight—far surpassing the 20 W/kg output of an Olympic rower. Remarkably, around 80% of this energy is lost as heat, which bees harness to regulate body and nest temperatures. (Seeley, 2019). Due to their hairy insulation (made from hairlike protrusions of their chitin exoskeleton (Hines et al., 2022)), bee thoraxes inevitably get 10-15°C warmer than the ambient temperature during flight (Seeley, 2019). The trade-off of their flight-muscle enzymes having evolved to withstand these elevated temperatures is that these enzymes have become inefficient at lower temperatures. Because of this, bees must preheat their thoraxes to at least 27°C to be able to fly. Honeybees warm themselves by simultaneously activating their wing-levator and wing-depressor muscles. Since these opposing muscles contract isometrically, they produce heat without wing vibrations (Seeley, 2019). In tandem with other worker bees, this same mechanism becomes a colony-wide method of thermoregulation.  

Fig. 14 Infrared camera thermogram of worker bees on a comb containing capped brood cells and empty cells. Capped cells, being warmer than empty cells, appear lighter. Similarly, bees warming their brood (bees A and B) have lighter-coloured thoraxes (Seeley, 2019). 

To survive the frigid winter months, bees must maintain their nest microclimate warm (34°C for the brood and above 8-18°C for the workers, for reasons previously mentioned). They do so by clustering themselves around the brood (if overwintering with brood) in a spherical shape while heating their thoraxes, increasing their clustering and heating intensity the lower the temperature. By pressing their bodies together, bees not only reduce their thermal radiation surface area but also their heat loss from air currents (convection) and conduction. Observations by Charles D. Owens have shown that bee clusters are composed of an outer zone of densely packed layers of bees forming an insulation blanket with a temperature gradient of 7-16°C that protects the warmer, inner zone of bees that have more space to crawl around, fan their wings, and care for their larvae. With the heat conductance of a 17,000-bee winter cluster estimated at 0.10 W/Kg°C, a bee superorganism’s outer layer rivals the insulation effectiveness of a comparatively sized bird’s feathers or mammal’s fur (Fig. 15) (Seeley, 2019).  

Fig. 15 Anatomy of a bee winter cluster inside a Langstroth hive at -21°C ambient temperature showing heat dissipative processes. Dark shading indicates the dense outer layer of the cluster, and the overwintering brood nest is situated inside the 32°C isotherm (Seeley, 2019). 

Cooling Down 

To combat the summer heat, honeybees have a distinct set of operations that they deploy in a graded response to keep the nest temperature under control. First, they do the opposite of clustering: dispersing. Workers spread out and partially evacuate the hive, thereby reducing metabolic heat production in the den and facilitating heat loss by convection (Seeley, 2019).  

Their next tactic is fanning. Ventilator bees organize themselves to fan in chains following the hive’s existing air currents. Other bees place themselves at the entrance to pull air out of the nest. Fanning bees cluster near one side of small nest entrances to optimize ventilation. This way, ventilation efficiency is increased from the air entering and exiting at different extremities of the hole, in addition to the air fluid friction being reduced. Surprisingly, entrance ventilators’ efficient partitioning results not from direct peer-to-peer communication, but from each worker sensing the air temperature and aligning themselves where it is the hottest (Fig. 16). By working together, bees can create an entrance airflow velocity as high as 3 meters per second and displace a volume of air of up to 1.0-1.4 litres per second through the hive. We should note that bees also ventilate to reduce carbon dioxide concentrations. Due to its high bee density, a nest’s CO₂ content when not actively ventilated is 0.7-1.0%, which is 20-30 times higher than the average CO₂ concentration in the atmosphere (Seeley, 2019).  

Bees’ trump card against the heat is evaporative cooling. Since water requires a lot of energy to vaporize, water evaporation is an effective cooling method (used when we sweat). Some older worker bees are water-collecting specialists who scour the land for water sources and fill their crops with water instead of nectar to bring back to the colony. Back in the hive, they transfer their load to workers who will hydrate thirsty comrades by trophallaxis (mouth-to-mouth regurgitation of liquid food) and disperse water to evaporate over combs. Other workers act as reservoirs, storing water for future use, in addition to the water stored in some comb cells (Seeley, 2019). 

Fig. 16 Top: Worker bees ventilating a hive’s entrance, clustering on the left side of the opening. Bottom: Air velocity (green), bee density (black), and air temperature (red) across the hive entrance (Seeley, 2019). 

For the Colony!

A beehive is an attractive meal for predators big and small. The dense packing of bees and larvae facilitates the spread of diseases and parasites while the sweet, sweet honey attracts animals ranging from wasps to bears. Because making beeswax combs is an enormous energy expenditure, and moving the stored brood and honey would be an equivalent feat, bees cannot afford to flee. They must stand and fight. Thus, bees have developed an arsenal of strategies to counter their evolutionary foes (Seeley, 2019). 

In addition to accelerating the brood growth, bees can rise their brood nest temperature by using their flight muscles to function as a colony-level fever to hinder the spread of brood diseases such as the chalkbrood fungus. Maintaining appropriate hygiene is another effective strategy for keeping diseases at bay. Wild bees clean their nest combs during winter, which kills the fungus during its resting stage. A different bee parasite, Varroa mites, feeds on bee hemolymph and are vectors of viruses (Fig. 17). Bees defend themselves against Varroa mites depending on the mite’s reproductive stage: bees bite off the mite’s legs and antennae when they attach to adult bees (grooming), and disrupt the mites sealed in brood cells by opening the cells up and possibly removing the infested bee larvae (Seeley, 2019). 

Fig. 17 Adult female of the Varroa destructor mite on a worker honeybee’s abdomen. The mite is circled in blue (Seeley, 2019). 

Bees have other defensive mechanisms for larger insects. To dislodge curious ants too close to the hive’s entrance, worker bees create blasts of air by posturing similarly to how they would ventilate the nest to then fan their wings rapidly (Breed et al., 2004). Apis florea bees also employ propolis (plant resin) to deter ants from the branches around their nest (Breed et al., 2004). Bees make propolis by collecting resin from various plants and storing it in their pollen baskets. Additionally, bee use resin to construct cages that trap invading beetles and mites (Breed et al., 2004). To prevent hornets from landing in their nests, honeybees synchronously raise their abdomens in masses at their hive entrance to create a deterrent ripple effect (Breed et al., 2004). Against the most aggressive hornets, bees (especially Japanese honeybees) can fry them alive (Kamioka et al., 2022). A technique called “the hot bee ball” is executed in multiple steps (Kamioka et al., 2022). At the sighting of a hornet, worker bees warm their flight muscles so that when the intruder enters the nest, around 500 prepared bees surround it (Kamioka et al., 2022). They rapidly raise the ball’s inner temperature, which can reach 46°C, for a duration of 30 minutes to kill the hornet (Fig. 18) (Kamioka et al., 2022). Although some defending bees also die, this variation of the bee thermoregulation clustering behaviour is an effective hornet counter (Kamioka et al., 2022). 

Fig. 18 Hot defensive bee ball used against a hornet by the Japanese honeybee, A. cerana japonica (Kamioka et al., 2022). 

Against larger predators such as vertebrates, bees may bite and chase in flight, but their most well-known defence is by far their sting. To ensure their sting remains an effective deterrent regardless of the aggressor’s size, honeybee stingers exhibit several anatomical adaptations. Indeed, large predators may still easily crush attacking bees. Honeybees overcome the goliath by attacking in a group, but they also have a stinger that can detach and sting autonomously, even if the soldier bee is removed (Ramirez-Esquivel & Ravi, 2023). To do so, the stinger must be able to pierce vertebrate skin without buckling, pump venom quickly, and coordinate the muscle stinging response, all in an enclosed, detachable unit. The portion of the stinger that is inserted into the tissue is comprised of 2 lancets and a stylet (Fig. 19). To penetrate the tissue, the lancets alternate in protracting and retracting. They have rearward-facing barbs which anchor into the tissue on retraction and pull the lancets further in. As the lancets penetrate, venom flows out from between them. The reciprocal action puts one lancet in tension while the other is in compression, which stabilizes the piercing parts and prevents buckling. To resist breakage, the piercing organs have a variable elasticity and hardness throughout their length, with the proximal end being the most elastic (since it receives the most bending stresses) and the distal end being harder. This variability is believed to derive from a metal enrichment of the cuticle with iron, copper, and manganese (Ramirez-Esquivel & Ravi, 2023). 

Fig. 19 Anatomy of the piercing parts of the honeybee stinger. The barbs are shown by arrows on images C and D (Ramirez-Esquivel & Ravi, 2023). 

Conclusion

Bees may seem like ordinary creatures whose daily behaviours consist of and honey creation; however, this perspective overlooks the complexity of these insects. By adopting specific wingbeat amplitudes, frequencies, and stroke patterns, bees manage to sustain their flight, carry heavy loads, and adapt smoothly to ever-changing flight conditions. To forage over vast territories, they utilize natural electromagnetic phenomena, such as sunlight polarization and geomagnetic poles, as compasses. Bees use airflows and electric fields throughout their waggle dance, an extraordinary form of communication, to share the location of resources with their hive. Despite their insulative habitat, they can detect and interpret their electrical information using specialized sensory mechanisms. When moving to a new colony, bee swarms create cluster structures which enable them to withstand harsh outdoor forces. As a colony, they apply principles of thermodynamics to protect their hive from extreme temperatures and predators. These strategies can provide insights for developing ultra-lightweight aerial machines and more manoeuvrable aircrafts, and have inspired novel, sunlight-based navigation systems (Kong et al, 2023). By exploiting physical principles to their advantage, bees demonstrate that one tiny creature can have the power of a mighty superorganism. 

References

Altshuler, D. L., Dickson, W. B., Vance, J. T., Roberts, S. P., & Dickinson, M. H. (2005). Short-amplitude high-frequency wing strokes determine the aerodynamics of honeybee flight. Proc Natl Acad Sci U S A, 102(50), 18213-18218. https://doi.org/10.1073/pnas.0506590102  

Breed, M. D., Guzmán-Novoa, E., & Hunt, G. J. (2004). Defensive behavior of honey bees: organization, genetics, and comparisons with other bees. Annu Rev Entomol, 49, 271-298. https://doi.org/10.1146/annurev.ento.49.061802.123155  

Chin, D. D., & Lentink, D. (2016). Flapping wing aerodynamics: from insects to vertebrates. J Exp Biol, 219(Pt 7), 920-932. https://doi.org/10.1242/jeb.042317  

Collin, S. P. (2010). Electroreception in Vertebrates and Invertebrates. In M. D. Breed & J. Moore (Eds.), Encyclopedia of Animal Behavior (pp. 611-620). Academic Press. https://doi.org/https://doi.org/10.1016/B978-0-08-045337-8.00323-5 

Crall, J. D., Chang, J. J., Oppenheimer, R. L., & Combes, S. A. (2017). Foraging in an unsteady world: bumblebee flight performance in field-realistic turbulence. Interface Focus, 7(1), 20160086. https://doi.org/10.1098/rsfs.2016.0086  

Dalven, R. (1990). Ferromagnetic Materials. In R. Dalven (Ed.), Introduction to Applied Solid State Physics: Topics in the Applications of Semiconductors, Superconductors, Ferromagnetism, and the Nonlinear Optical Properties of Solids (pp. 347-390). Springer US. https://doi.org/10.1007/978-1-4684-1330-4_10 

Dickinson, M.H., Lehmann F.-O., & Sane, S.P. (1999). Wing rotation and the aerodynamic basis of insect flight. Science, 284(5422), 1954-1960. https://doi.org/10.1126/science.284.5422.1954  

England, S. J., & Robert, D. (2022). The ecology of electricity and electroreception. Biological Reviews, 97(1), 383-413. https://doi.org/https://doi.org/10.1111/brv.12804 

Frisch, K. v. (1993). The dance language and orientation of bees. Harvard University Press.  

Fry, S. N., Sayaman, R., & Dickinson, M. H. (2005). The aerodynamics of hovering flight in Drosophila. J Exp Biol, 208(Pt 12), 2303-2318. https://doi.org/10.1242/jeb.01612  

Glass, J. R., Burnett, N. P., Combes, S. A., Weisman, E., Helbling, A., & Harrison, J. F. (2024). Flying, nectar-loaded honey bees conserve water and improve heat tolerance by reducing wingbeat frequency and metabolic heat production. Proc Natl Acad Sci U S A, 121(4), e2311025121. https://doi.org/10.1073/pnas.2311025121  

Goldstein, D. H. (2017). Polarized light. CRC press. 

Greggers, U., Koch, G., Schmidt, V., Dürr, A., Floriou-Servou, A., Piepenbrock, D., Göpfert, M. C., & Menzel, R. (2013). Reception and learning of electric fields in bees. Proc Biol Sci, 280(1759), 20130528. https://doi.org/10.1098/rspb.2013.0528  

Heinze, S. (2013). Polarization . In D. Jaeger & R. Jung (Eds.), Encyclopedia of Computational Neuroscience (pp. 1-30). Springer New York. https://doi.org/10.1007/978-1-4614-7320-6_334-5 

Hines, H. M., Kilpatrick, S. K., Mikó, I., Snellings, D., López-Uribe, M. M., & Tian, L. (2022). The diversity, evolution, and development of setal morphologies in bumble bees (Hymenoptera: Apidae: Bombusspp.). PeerJ, 10, e14555. https://doi.org/10.7717/peerj.14555 

Hung, Y. S., & Ibbotson, M. R. (2014). Ocellar structure and neural innervation in the honeybee. Front Neuroanat, 8, 6. https://doi.org/10.3389/fnana.2014.00006 

Hsu, C.-Y., Ko, F.-Y., Li, C.-W., Fann, K., & Lue, J.-T. (2007). Magnetoreception system in honeybees (Apis mellifera). PloS one, 2(4), e395. 

Kamioka, T., Suzuki, H. C., Ugajin, A., Yamaguchi, Y., Nishimura, M., Sasaki, T., Ono, M., & Kawata, M. (2022). Genes associated with hot defensive bee ball in the Japanese honeybee, Apis cerana japonica. BMC Ecology and Evolution, 22(1), 31. https://doi.org/10.1186/s12862-022-01989-9 

Kraft, P., Evangelista, C., Dacke, M., Labhart, T., & Srinivasan, M. V. (2011). Honeybee navigation: following routes using polarized-light cues. Philos Trans R Soc Lond B Biol Sci, 366(1565), 703-708. https://doi.org/10.1098/rstb.2010.0203 

Klowden, M. J., & Palli, S. R. (2023). Chapter 11 – Nervous systems. In M. J. Klowden & S. R. Palli (Eds.), Physiological Systems in Insects (Fourth Edition) (pp. 527-605). Academic Press. https://doi.org/https://doi.org/10.1016/B978-0-12-820359-0.00005-0 

Kong, F., Guo, Y., Zhang, J., Fan, X., & Guo, X. (2023). Review on bio-inspired polarized skylight navigation. Chinese Journal of Aeronautics, 36(9), 14-37. https://doi.org/https://doi.org/10.1016/j.cja.2023.05.024 

Lambinet, V., Hayden, M. E., Reid, C., & Gries, G. (2017). Honey bees possess a polarity-sensitive magnetoreceptor. Journal of Comparative Physiology A, 203(12), 1029-1036. https://doi.org/10.1007/s00359-017-1214-4 

Land, M. F. (2009). Chapter 96 – Eyes and Vision. In V. H. Resh & R. T. Cardé (Eds.), Encyclopedia of Insects (Second Edition) (pp. 345-355). Academic Press. https://doi.org/https://doi.org/10.1016/B978-0-12-374144-8.00105-3 

Liang, C.-H., Chuang, C.-L., Jiang, J.-A., & Yang, E.-C. (2016). Magnetic Sensing through the Abdomen of the Honey bee. Scientific Reports, 6(1), 23657. https://doi.org/10.1038/srep23657 

Ma, Y., Ren, H., Rajabi, H., Zhao, H., Ning, J., & Gorb, S. (2019). Structure, properties and functions of the forewing-hindwing coupling of honeybees. J Insect Physiol, 118, 103936. https://doi.org/10.1016/j.jinsphys.2019.103936  

Magnan, A. (1934). La locomotion chez les animaux. Hermann.  

Menzel, R., & Snyder, A. W. (1974). Polarised light detection in the bee,Apis mellifera. Journal of comparative physiology, 88(3), 247-270. https://doi.org/10.1007/BF00697958 

Michelsen, A. (2014). Mechanical Signals in Honeybee Communication. In R. B. Cocroft, M. Gogala, P. S. M. Hill, & A. Wessel (Eds.), Studying Vibrational Communication (pp. 333-347). Springer Berlin Heidelberg. https://doi.org/10.1007/978-3-662-43607-3_17  

Michelsen, A., Towne, W. F., Kirchner, W. H., & Kryger, P. (1987). The acoustic near field of a dancing honeybee. Journal of Comparative Physiology A, 161(5), 633-643. https://doi.org/10.1007/BF00605005  

Peleg, O., Peters, J., Salcedo, M., & Mahadevan, L. (2018). Collective mechanical adaptation of honeybee swarms. Nature Physics, 14. https://doi.org/10.1038/s41567-018-0262-1  

Peters, J. M., Peleg, O., & Mahadevan, L. (2022). Thermoregulatory morphodynamics of honeybee swarm clusters. Journal of Experimental Biology, 225(5), jeb242234. https://doi.org/10.1242/jeb.242234  

Ramirez-Esquivel, F., & Ravi, S. (2023). Functional anatomy of the worker honeybee stinger (Apis mellifera). iScience, 26(7), 107103. https://doi.org/10.1016/j.isci.2023.107103 

Ravi, S., Crall, J. D., Fisher, A., & Combes, S. A. (2013). Rolling with the flow: bumblebees flying in unsteady wakes. J Exp Biol, 216(Pt 22), 4299-4309. https://doi.org/10.1242/jeb.090845  

Ribi, W., Warrant, E., & Zeil, J. (2011). The organization of honeybee ocelli: Regional specializations and rhabdom arrangements. Arthropod Structure & Development, 40(6), 509-520. https://doi.org/https://doi.org/10.1016/j.asd.2011.06.004 

Ristroph, L., Ristroph, G., Morozova, S., Bergou, A. J., Chang, S., Guckenheimer, J., Wang, Z. J., & Cohen, I. (2013). Active and passive stabilization of body pitch in insect flight. J R Soc Interface, 10(85), 20130237. https://doi.org/10.1098/rsif.2013.0237  

Seeley, T. D. (2019). The lives of bees : the untold story of the honey bee in the wild. Princeton University Press. 

Shah, M., Battaglia, F., & Bayandor, J. (2023). The Importance of Morphology in Further Unraveling the Bumblebee Flight Paradox. Journal of Fluids Engineering, 145(1). https://doi.org/10.1115/1.4055548  

Sotavalta, O. (1952). Flight-tone and wing-stroke frequency of insects and the dynamics of insect flight. Nature, 170(4338), 1057-1058. https://doi.org/10.1038/1701057a0 

Sutton, G. P., Clarke, D., Morley, E. L., & Robert, D. (2016). Mechanosensory hairs in bumblebees (<i>Bombus terrestris</i>) detect weak electric fields. Proceedings of the National Academy of Sciences, 113(26), 7261-7265. https://doi.org/doi:10.1073/pnas.1601624113 

Visscher, P. K. (2009). Chapter 66 – Dance Language. In V. H. Resh & R. T. Cardé (Eds.), Encyclopedia of Insects (Second Edition) (pp. 248-251). Academic Press. https://doi.org/https://doi.org/10.1016/B978-0-12-374144-8.00075-8  

Warrant, E. (2019). Invertebrate Vision☆. In J. C. Choe (Ed.), Encyclopedia of Animal Behavior (Second Edition) (pp. 64-79). Academic Press. https://doi.org/https://doi.org/10.1016/B978-0-12-809633-8.01303-0 

Winston, M. L. (1991). The Biology of the Honey Bee. Harvard University Press.  

Zakon, H. H. (2016). Electric fields of flowers stimulate the sensory hairs of bumble bees. Proc Natl Acad Sci U S A, 113(26), 7020-7021. https://doi.org/10.1073/pnas.1607426113