Peer-reviewed biological studies document honey bees successfully and actively flying in various environmental conditions, directly refuting the myth that aerodynamic principles prohibit them from flying.
ABSTRACT While multiple studies have shown that honey bees and some other flying insects lower their flight metabolic rates when flying at high air temperatures, critics have suggested such patterns result from poor experimental methods as, theoretically, air temperature should not appreciably affect aerodynamic force requirements. Here, we show that apparently contradictory studies can be reconciled by considering the thermal performance curve of flight muscle. We show that prior studies that found no effects of air temperature on flight metabolism of honey bees achieved flight muscle temperatures that were near or on equal, opposite sides of the thermal performance curve. Honey bees vary their wing kinematics and metabolic heat production to thermoregulate, and how air temperature affects the flight metabolic rate of honey bees is predictable using a non-linear thermal performance perspective of honey bee flight muscle.
10.1242/jeb.247741 10.1242/jeb.247756 ABSTRACT While multiple studies have shown that honey bees and some other flying insects lower their flight metabolic rates when flying at high air temperatures, critics have suggested such patterns result from poor experimental methods as, theoretically, air temperature should not appreciably affect aerodynamic force requirements. Here, we show that apparently contradictory studies can be reconciled by considering the thermal performance curve of flight muscle.
In the present study, and in our recent studies ( Glass and Harrison, 2022 ; Glass et al., 2024 ), we address this decades-old controversy. Harrison and colleagues (1996a , b ) found that honey bees decrease wingbeat frequency as well as flight metabolic rate in response to high air temperatures. However, critics raised doubts that wingbeat frequency declines with air temperature ( Heinrich and Esch, 1997 ), pointing out that the aerodynamic force requirements, and thus work, for animal flight are nearly independent of air temperature ( Ellington, 1984 ; Dudley, 2000 ).
In response to these criticisms, Roberts and Harrison (1999) hypothesized that honey bees decrease their wingbeat frequency to reduce metabolic heat production when flying in the heat while adjusting other kinematic contributions, such as increasing their stroke amplitude, potentially allowing honey bees to fly more efficiently when things get hot. Until recently, no study had measured the metabolic and kinematic responses of honey bees flying at high air and flight muscle temperatures ( Glass et al., 2024 ).
We now know that honey bees flying at 40°C air temperature can lower their flight metabolism by decreasing their wingbeat frequency by about 10% and increasing their stroke amplitude by the same amount, allowing hot bees to generate the same amount of aerodynamic force as bees flying in cooler conditions ( Glass et al., 2024 ). With this knowledge, we can begin to reconcile the differences between these studies in light of the thermal performance curve for flight metabolism in honey bees ( Glass and Harrison, 2022 ).
Data standardization Data from Glass and Harrison (2022) represent maximal aerobic performance for unloaded flying honey bees (see below for a brief description of these methods). These maximal aerobic performance estimates came from measurements of flight metabolism in which we flew honey bees in decreasing air densities. Flight in low-density air requires bees to generate higher mechanical power, eliciting maximal aerobic performance in the lowest density air (25–40% higher metabolic rates than for bees flown at normal air density; Roberts et al., 2004 ).
Although Woods and colleagues (2005) measured the flight muscle temperatures of bees immediately after recording their flight metabolic rates, they did not include a single figure showing the relationship between flight metabolic rate and flight muscle temperature in their original study. To generate the Woods et al. (2005) data, we extracted their reported flight muscle temperatures ( n= 34) and mass-specific flight metabolic rates ( n =19) for bees flying at different air temperatures and compared the air temperature at which each bee was flown.
Immediately after measuring carbon dioxide production, the researchers shook the bee into a bag and measured its flight muscle temperature with a
After the flight metabolic trial, they shook the bee into a plastic bag and measured its body temperature with a hypodermic thermocouple within 10 s after the bee had stopped flying. Glass and Harrison (2022) methods Glass and Harrison (2022) ran experiments using three hives of honey bees maintained at Arizona State University, Tempe, USA. The researchers used gas cylinders of oxygen, nitrogen and helium and an 8-channell mass-flow controller (Flow-Bar 8, Sable Systems International) to create variable-density gas mixtures (range 0.441–1.288 kg m −3 ) to elicit maximal flight performance.
RESULTS AND DISCUSSION Data for summer-caught honey bees flying freely at different air temperatures from Heinrich (1980) and from Woods et al. (2005) suggest that flight metabolism is independent of air temperature ( Fig. 2A ). In contrast, the data presented in this study show a negative effect, with flight metabolic rates decreasing as the bees fly at higher air temperatures ( Fig. 2A ). Fig. 2. Effect of air temperature on flight metabolic rate and flight muscle temperature. (A) Heinrich (1980) and Woods et al.
However, the extent to which flight muscle temperature increases with air temperature differed among these studies (‘study’×air temperature interaction – generalized linear model: n =190, d.f.=1, χ 2 =30.4, P <0.0001; Table S1 ). Here, we show that the mass-specific metabolic response of flying honey bees to changes in flight muscle temperature is asymmetric and non-linear and that the relative change in response depends on the temperature of the bee relative to the optimal temperature for aerobic performance ( Fig. 3 ; Tables S2, S3 ).
Simple Summary We investigated how honey bees (Apis mellifera) adapt their behavior when navigating to a sugar-rich food source in the presence of wind that disrupts their flight path. To explain this behavior, we applied Perceptual Control Theory (PCT), which posits that organisms actively pursue goals rather than merely respond to external stimuli. In our experiment, 13 of 14 bees successfully adjusted their flight paths to reach the food source despite the wind. The bees tested various approach strategies but ultimately favored flying directly into the wind, rather than allowing it to push them from behind or the side. Consistent with PCT principles, our findings indicate that honey bee behavior is self-regulating and adaptable, resembling a dynamic adjustment process rather than a linear cause-and-effect sequence. As PCT emphasizes the purpose of behavior, it can also be described as goal-directed (teleonomic).
Simple Summary We investigated how honey bees ( Apis mellifera ) adapt their behavior when navigating to a sugar-rich food source in the presence of wind that disrupts their flight path. To explain this behavior, we applied Perceptual Control Theory (PCT), which posits that organisms actively pursue goals rather than merely respond to external stimuli. In our experiment, 13 of 14 bees successfully adjusted their flight paths to reach the food source despite the wind. The bees tested various approach strategies but ultimately favored flying directly into the wind, rather than allowing it to push them from behind or the side.
Consistent with PCT principles, our findings indicate that honey bee behavior is self-regulating and adaptable, resembling a dynamic adjustment process rather than a linear cause-and-effect sequence. As PCT emphasizes the purpose of behavior, it can also be described as goal-directed (teleonomic). Abstract Self-regulatory foraging behavior in honey bees ( Apis mellifera ) was investigated using the framework of Perceptual Control Theory (PCT). We developed a PCT-based model to describe how bees maintain goal-directed behavior, specifically targeting a sucrose-rich feeding site while overcoming a wind disturbance.
In a controlled experiment, we found that 13 of 14 bees could successfully adjust their flight paths to overcome the disturbance and consistently reach the feeding target. While they demonstrated a great deal of individual variability regarding how they overcame the wind across experimental trials, they did so by finally adopting a headwind (i.e., flying into the wind) approach pattern rather than tailwind or crosswind approach patterns. These results support the application of PCT to the study of behavior in honey bees, which can be regarded as self-regulative (i.e., non-linear and dynamic) rather than as linear sequences of inputs and outputs.
Approaches and Direction Examination of the recorded videos revealed that the bees varied the rates (i.e., their speeds) at which they flew through the wind as well as the direction from which they approached the target. The bees could also be seen pushing against the wind, being pushed back, and then pushing forward again through the wind.
By the final trial (Trial #12), the majority of bees still used the headwind approach more frequently than the tailwind (PCC = 69.23, c = 0.03), right side (PCC = 76.92, c = 0.01), or left side (PCC = 76.92, c < 0.01), although the results were not as pronounced. As a general test of the headwind preference across all twelve
In this case the controlled variable was the distance between the bee’s current position and the target, and the ideal distance was a value of ‘0’ (i.e., no distance from the target). In accord with the negative feedback loop in Figure 1 , the bees achieved this internal standard by varying the direction which they approached the target and the speed of their flight to overcome the 3.6 m/s wind and reach the target. Results revealed the bees preferred to approach the target by flying into the wind as a means for counteracting the disturbance.
The fan position was moved (i.e., disturbed) every three trials to a new position, but regardless of the position the bees still approached into the wind more than any other direction; meaning, the bees were not approaching the target consistently from the same direction (e.g., from the back side of the landing platform); but rather, they varied their approaches to match a preferred approach (viz., approach into wind). From the observational data, the bees were seen varying the speeds with which they were flying, pushing against the wind to get closer to the target, getting pushed back, and then pushing forward again and eventually landing.
During flight the bees must also control their stability by varying their body position (i.e., pitch and yaw). Consistent with the fundamental laws of aerodynamics, by approaching into the wind the bees will have greater stability when landing, the same as an airplane approaching a runway. Similarly, it is easier to respond to and counteract harsh changes (e.g., a crosswind) when flying into the wind than it is in other directions. Finally, flying into the wind (whether landing or taking off) has a well-known impact on lift and drag, which are important variables for flight (see [ 34 , 35 , 36 ]).
In any given moment, each bee is simultaneously controlling all of these variables (among others) in harmony and in the context of continuously changing environmental feedback. With such complexity, individual variability is to be expected. Generally speaking, results from studies regarding the flying dynamics of honey bees comport well with PCT. For instance, when flying through tunnels, bees maintain equidistance from the walls by balancing perceived image speeds, controlling flight position to match a centered reference [ 37 ]. Flight speed is regulated by holding average image velocity constant, reducing collision risks by stabilizing optic flow perception.
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