The sleep of bees (Apis mellifera)

By Claude Pfefferlé and Serge Imboden

Long regarded as a model of uninterrupted activity, the honey bee nevertheless continues to surprise researchers. Recent studies have revealed that it sleeps, and that this sleep plays an essential role in regulating its memory, physiology, and group cohesion. Understanding how and why bees sleep is to open a window onto the health of the hive—and onto the balance of life itself.

1. From the myth of the tireless bee to the discovery of sleep

Since Antiquity, the bee has embodied the symbol of relentless work: organized, disciplined, tireless. Fables, school textbooks, and speeches about the “ideal society” have turned it into the image of a population wholly devoted to activity. Yet this heroic vision has proven inaccurate.

Recent advances in ethology and neurobiology have overturned this myth: the honey bee (Apis mellifera) does indeed sleep (Kaiser, 1988 ; Klein & Busby, 2020 ; Carcaud et al., 2023). This sleep is neither accidental nor marginal, but a vital process for the balance of the colony. It is accompanied by precise behavioral criteria: an immobile posture, relaxed antennae, slowed respiration, and reduced sensory responsiveness (Eban-Rothschild & Bloch, 2008 ; Kaiser, 1988). For a long time, these rest periods went unnoticed because they occurred in the darkness of the hive, at hours when the human observer was absent.

The first objective evidence was provided in the 1980s by Walter Kaiser: using electromyographic recordings, he distinguished different levels of muscular activity, from simple rest to deep sleep (Kaiser, 1988). These observations made it possible to define the first scientific framework for sleep in Apis mellifera. They show that, like vertebrates, bees have an internal regulatory mechanism: after sleep deprivation, they sleep longer to compensate for the deficit, a phenomenon known as “homeostatic rebound” (Eban-Rothschild & Bloch, 2008).

Sleep therefore cannot be reduced to an energetic pause. It supports memory, coordination, and group stability. A well-rested bee navigates better, dances more precisely, and communicates more effectively (Klein et al., 2010 ; Zwaka et al., 2015). At the colony scale, these individual differences translate into a measurable improvement in collective performance: orientation, foraging, thermoregulation (Yaniv et al., 2022 ; Stabentheiner et al., 2021).

This reversal of perspective has profound implications. It reminds us that the hive is not a production machine, but a living organism subject to physiological cycles. Understanding bee sleep means understanding how nature balances activity and rest, wakefulness and silence. In a world where apiaries are often exposed to artificial light, vibrations, and frequent interventions, rediscovering this fundamental need amounts to restoring bees’ right to calm (Carcaud et al., 2023 ; Zwaka et al., 2015).

2. Behavioral and physiological signs of sleep

While the existence of sleep in Apis mellifera is no longer in doubt, its concrete expression remains fascinating. Researchers distinguish several levels of rest, from simple muscular relaxation to deep sleep comparable to that of vertebrates (Kaiser, 1988 ; Eban-Rothschild & Bloch, 2008 ; Klein & Busby, 2020).

A sleeping bee adopts a typical posture: head tilted, antennae drooping, wings lowered, front legs weakly hooked to the support. The antennae, normally in constant motion, become immobile—a sign of reduced sensory vigilance and a slowing of metabolism (Kaiser, 1988 ; Klein et al., 2010).

Illustration 1: Sleeping bee (head tilted, antennae drooping, wings lowered, front legs weakly hooked) Souce : generated by AI

Thermographic measurements reveal a decrease of one to two degrees in thoracic temperature during sleep: a collective energy saving analogous to that observed in mammals (Stabentheiner et al., 2021). These wake–sleep cycles repeat several times a day, synchronized by the alternation of light and darkness and by internal signals of the colony (Yaniv et al., 2022).der Text

Some workers sleep inside the cells themselves: this “cell sleep,” described by Klein & Busby (2020), represents about 15% of the time spent in the wax. The cells provide a stable microclimate conducive to recovery and show that the hive is not a space of continuous activity, but an organism paced by rest and silence (Carcaud et al., 2023).

Illustration 2 : (A) Clear view of the posterior tip of the abdomen of a worker in the center. This is the typical view of an adult bee inside a cell when frames are removed from a hive or—here—when looking through the window of an observation hive (Würzburg, Germany, 2006). (B–D) Exceptionally clear views of bees sleeping inside cells built on the windows of an observation hive

Illustration 2: Visibility of worker bees at the bottom of cells in observation hives. Photos by Barrett Klein.

Sleep varies by caste and social function. Nurses, young workers attending the brood, sleep little but often: their micro-naps are fragmented across the 24-hour cycle and modulated by larval pheromones that stimulate their wakefulness (Eban-Rothschild & Bloch, 2008 ; Traynor et al., 2014).

Foragers, older workers, show consolidated nocturnal sleep; its depth increases with fatigue and conditions the precision of the waggle dance the next day (Klein et al., 2010). Some foragers, too far from the nest at dusk, fall asleep outdoors. Clinging to a flower or a stem, they lower their antennae and become completely still. This substitute sleep, though risky, allows them to recover before the return flight. These observations highlight the behavioral flexibility of Apis mellifera: even rest adapts to environmental constraints (Klein et al., 2014).

The queen, whose activity is almost continuous, alternates brief, weakly circadian phases of metabolic rest; the queen pheromones she emits stabilize collective rhythms (Johnson et al., 2010 ; Cardoso-Junior et al., 2020). Behavioral recordings suggest that these pauses, often lasting only a few seconds to a few minutes, correspond to genuine phases of muscular relaxation and metabolic downshifts—a form of fragmented micro-sleep rather than consolidated sleep onset.

Illustration 3 : If necessary, foragers also sleep in flowers. Generated by AI.

As for drones, they sleep for long periods outside their nuptial flights, often clustered in the cooler peripheral zones of the hive. Their rest depends strongly on ambient temperature (Fahrenholz et al., 1989). Their wake–sleep cycle follows a well-marked circadian rhythm: most males become active simultaneously in mid-afternoon for reproductive flights, then remain inactive the rest of the time (Neubauer et al., 2023).

Finally, in winter, sleep becomes collective: bees at the center of the cluster sleep in episodes while those at the periphery generate the heat needed for survival (Oliver, 2016 ; Minaud et al., 2024). This ongoing choreography between rest and activity embodies the living thermoregulation of the superorganism.

Thus, bee sleep is not a simple state of torpor, but an integrated mechanism of physiology and social cohesion: each individual rests a little so that the hive, as a whole, remains continually attentive to life. (Seeley, 2019).

3. Neural bases and cognitive functions of sleep

Behind the apparent immobility of a sleeping bee lies surprisingly ordered brain activity. Recent advances in neurobiology have made it possible to observe, for the first time, neural signatures of sleep in Apis mellifera (Carcaud et al., 2023 ; Kaiser, 1988 ; Klein & Busby, 2020). Using microelectrodes and two-photon calcium imaging, researchers identified distinct cycles of brain activity comparable to those observed during slow-wave sleep in vertebrates (Carcaud et al., 2023).

The bee brain, though tiny, contains specialized structures: the antennal lobes, dedicated to odor processing, and the mushroom bodies, true centers of memory and learning (Giurfa, 2015). During sleep, these regions do not shut down: they synchronize. Neural activity becomes more coherent, sensory responsiveness attenuates, and metabolism stabilizes. Carcaud et al. (2023) showed that wake and rest states can be distinguished with over 90% reliability by analyzing antennal lobe dynamics. During rest, neurons communicate more harmoniously, as if the brain were “recalibrating” its circuits after the agitation of the day.

The neurotransmitter GABA plays a central role in this process. By reducing the excitability of motor and sensory circuits, it induces a gentle inhibition of the nervous system, allowing networks to rebalance (Kaiser, 1988 ; Klein & Busby, 2020). This mechanism, called neuronal homeostasis, is essential for behavioral and cognitive stability. The bee does not sleep to stop, but to maintain the accuracy of its neural connections.

Sleep-deprivation experiments confirm this function: after several hours of continuous activity, bees show reduced precision in the waggle dance and navigation errors (Klein et al., 2010). One night of rest is sufficient to restore performance. Sleep therefore acts as a tool of cognitive maintenance. It consolidates memory, strengthens olfactory learning, and improves social coordination (Eban-Rothschild & Bloch, 2008 ; Beyaert et al., 2012 ; Klein & Busby, 2020).

Illustration 4: Bee equipped with a radio-frequency identification (RFID) device. According to Beyaert et al., 2012, generated by AI

The study by Zwaka et al. (2015) even showed that the bee’s brain “replays,” during sleep, the olfactory experiences learned the previous day: bees exposed to a familiar odor during rest remembered it better the next day. This phenomenon of “mnestic reactivation” recalls what is observed in humans and other higher animals (Zwaka et al., 2015 ; Yaniv et al., 2022). Sleep thus appears as an active and restorative state of the brain, in which links are forged between learning, memory, and behavioral stability.

4. Social regulation and collective memory of sleep

In the hive, sleep is never an individual matter. Each bee sleeps at the heart of a dense environment of thermal, vibrational, and chemical signals that directly influence the quality and duration of its rest (Eban-Rothschild & Bloch, 2008 ; Klein & Busby, 2020). Research by Eban-Rothschild and Bloch (2012) showed that isolated bees sleep less and in a more fragmented manner than those integrated into a colony. Sometimes it is enough to expose them to hive air—saturated with pheromones—to restore a normal sleep rhythm. Bee rest is therefore socially synchronized.

Queen pheromones, continuously released by the queen and transmitted by contact among workers, have a calming effect on the entire group (Pankiw, 2004). They stabilize collective behavior and contribute to a form of social coherence. Conversely, larval pheromones stimulate nurses and temporarily reduce their sleep, ensuring constant attention to the brood (Traynor et al., 2014). Pheromones do not merely transmit behavioral information: they also modulate physiology. Some influence the expression of genes linked to circadian rhythm and neuronal plasticity, illustrating the depth of the link between social communication and the biology of rest (Yaniv et al., 2022).

In addition to chemical signals, bees exchange information through vibrations. Wing beats, leg movements, and the waggle dance generate mechanical waves that propagate through the wax (Tautz, 2008). These vibrations structure hive life: they coordinate thermoregulation, task allocation, and even phases of wakefulness and rest (Seeley, 2019 ; Stabentheiner et al., 2021). In a calm colony, vibrations are weak and regular. When danger arises—a knock on the hive, an intrusion, a predator—a stronger vibrational signal triggers an almost instantaneous collective awakening. This mechanism ensures that the hive remains partially vigilant even at night. One then speaks of “partial vigilance,” in which some sensory pathways remain active, notably those linked to alarm pheromones (Kirchner, 1993).

This rhythmic organization illustrates the emergent character of collective cognition: individual wake–sleep cycles interlock to produce coherence at the scale of the superorganism (Seeley, 2019 ; Yaniv et al., 2022). A well-rested colony communicates more effectively, shares foraging information better, and maintains a more stable spatial memory (Klein & Busby, 2020 ; Zwaka et al., 2015).

Sleep thus becomes a group phenomenon, comparable to a shared respiration. While some workers sleep, others provide guarding, ventilation, or brood care, maintaining minimal vigilance (Eban-Rothschild & Bloch, 2008). The alternation between activity and silence is not accidental, but an adaptive strategy: it allows the hive to remain ready without ever exhausting itself.

Human-origin disturbances—artificial light, mechanical vibrations, continuous noise—disorganize this synchronization (Zwaka et al., 2015 ; Yaniv et al., 2022). Bees become arrhythmic, sleep less, and communicate less well. Over the long term, this fragmentation of sleep weakens group cohesion and reduces resilience. Preserving the hive’s night is therefore also preserving the collective memory of life.

5. Winter sleep and thermoregulation

When winter sets in and flowers disappear, the bee colony withdraws: individuals stop their outside activities and form the winter cluster, a living sphere that ensures the survival of the group (Seeley, 2019 ; Stabentheiner et al., 2021). This phenomenon, unique among social insects, combines thermoregulation and rest (Oskin et al., 2022).

At the heart of the cluster, bees pack together so tightly that their thoraxes form a heat-conducting network. Those in the center benefit from a stable temperature, between 25 and 30 °C, and sleep in episodes interspersed with brief phases of activity (Oliver, 2016 ; Minaud et al., 2024). Workers on the periphery, exposed to the cold, contract their thoracic muscles to generate the heat needed for survival, then move toward the center when they tire—a continuous rotation that balances wakefulness and rest (Seeley & Visscher, 1985).

Illustration 5: At the heart of the cluster, bees sleep in episodes interspersed with brief phases of activity. Generated by AI.

The cluster “breathes” slowly: it contracts or expands depending on outside temperature (Oskin & Ovsyannikov, 2019). This collective movement keeps the hive alive even under extreme conditions (Stabentheiner et al., 2021). Thermographic observations show a core that is almost constant in temperature, while the periphery undergoes large variations. There, bees sleep little, in rapid micro-pauses (Mitchell, 2023). Sleep takes on a community dimension here: no bee truly hibernates, but the superorganism alternates phases of reduced activity and collective rest (Minaud et al., 2024 ; Seeley, 2019).

The queen remains at the center, fed by winter workers. Her egg laying stops: a sign of metabolic rest (Seeley, 2019). Winter bees, with slowed metabolism, live for several months thanks to a controlled consumption of honey reserves (DeGrandi-Hoffman et al., 2025). Any disturbance—opening, vibration, shock—breaks this balance: resuming heat production entails an irreversible energy loss (Seeley & Visscher, 1985 ; Oliver, 2016).

Colonies left undisturbed conserve their reserves better and survive more often (St. Clair et al., 2022). A simple precaution—avoiding winter manipulations—often makes the difference. This collective sleep embodies the thermal intelligence of life: without conscious coordination, thousands of bees constantly adjust rest and activity to maintain nest heat. Each individual sleeps a little so that the colony, as a whole, remains attentive to life.

6. Beekeeping of rest: practical recommendations

Recent knowledge about bee sleep no longer belongs solely to fundamental research: it opens the way to beekeeping that is more respectful of biological rhythms. Preserving the colony’s rest means improving its health, cohesion, and productivity (Eban-Rothschild & Bloch, 2012 ; Klein & Busby, 2020). A well-rested hive learns better, resists better, and works more efficiently the next day (Zwaka et al., 2015).

6.1 Observe without disturbing

Any observation influences colony behavior. Manipulations, vibrations, and artificial light interrupt collective sleep and disrupt circadian rhythms (Yaniv et al., 2022). To limit this impact, it is recommended to observe hives only when necessary, under calm conditions and without shocks. Transparent inner covers make observation easier without opening the hive. When an intervention is necessary, it is better to replace smoke with a light mist of lukewarm water, which calms without altering internal chemical signals.

6.2 Reduce light and vibration stressors

The studies by Kim et al. (2024) and Tackenberg et al. (2020) show that light reduces the duration and depth of sleep, while chronic vibrations induce a state of permanent vigilance. Placing hives away from streetlights, roads, or agricultural machinery thus becomes a health measure in its own right. Wooden or rubber supports dampen vibrations better than metal. Around the apiary, hedges or vegetated embankments help filter light and stabilize the nocturnal microclimate.

6.3 Limit chemical stressors

Pesticides and repeated treatments affect sleep physiology (Tackenberg et al., 2020 ; Klein & Busby, 2020). Neonicotinoids disrupt neural circuits involved in wakefulness and memory; even at low doses, they desynchronize the internal clock and reduce behavioral cohesion (Chakrabarti et al., 2015). Choosing locations away from treated crops, using gentle treatments, and limiting unnecessary interventions helps preserve natural cycles of rest and wakefulness.

6.4 Link rest and immunity

Regular sleep strengthens immune resistance (Evans & Spivak, 2010 ; Klein & Busby, 2020). Sleep-deprived colonies show higher viral loads and increased vulnerability to Varroa destructor (DeGrandi-Hoffman et al., 2025). Conversely, calm apiaries develop better social immunity: bees maintain more effective hygienic behaviors (cleaning, removal of infected larvae) and more stable thermoregulation (Stabentheiner et al., 2021).

6.5 Promote an ethics of calm

Beekeeping of rest is above all an attitude: intervene less, observe more (Seeley, 2019). Respecting nocturnal calm and the hive’s natural pauses means giving bees back the time to express their self-regulation mechanisms (Eban-Rothschild & Bloch, 2008). A colony left undisturbed sleeps better, communicates better, and survives better. This respect for internal rhythms is one of the best indicators of beekeeping sustainability (Seeley, 2019).

7. Conclusion

Bee sleep, long ignored, now appears as a pillar of their social biology. This phenomenon—neuronal, physiological, and collective at once—links the organizational levels of life: the individual body, the brain, the colony, and the ecosystem.
Recent advances have shown that sleep supports not only memory and coordination, but also the health and resilience of the group. A well-rested colony learns better, communicates more precisely, and resists external disturbances more effectively.

Conversely, artificial light, vibrations, and pesticides disrupt circadian rhythms, fragment rest phases, and weaken the cohesion of the superorganism. Lack of sleep does not translate into visible fatigue, but into a gradual loss of efficiency: less precise dances, erratic navigation, impaired brood care. These cumulative effects silently weaken the colony, sometimes more reliably than a food shortage.

Modern beekeeping has learned a great deal about nutrition, health, and selection, but little about rest. Yet the stability of an apiary depends not only on available resources, but also on respecting internal rhythms. Observing the sleeping hive is perceiving the breathing of a collective organism. Sustainable beekeeping should now integrate this invisible dimension: protect the night, reduce unnecessary stimuli, promote calm, and favor natural insulation.

In a world saturated with light and noise, bees remind us of an ecological self-evidence: the efficiency of living systems rests on the alternation between activity and silence.
Their sleep is not a weakness, but a form of wisdom. Respecting this rest time means reconnecting with the fundamental rhythm of life—the one that unites performance, memory, and the peace of the natural world.

Observations en temps réel

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