Everyone has heard the myth that bumblebees defy the laws of physics when they fly. Of course, we know that this is not the case, but we still know surprisingly little about how bumblebees fly in outdoor environments, where the weather can change abruptly. For a lightweight bumblebee, wind conditions are arguably the most important aspect of weather to consider and can alter very quickly – sometimes in seconds. So, how does the tiny bumblebee cope with these rapid and sometimes extreme changes, and what wind conditions do they actually experience while foraging outside the hive?
These are questions that a team of researchers from the USA wanted to address. Firstly, James Crall, Stacey Combes and colleagues fitted 87 Bombus impatiens bumblebees with radio identification tags and tracked them as they exited and entered the hive. Simultaneously, they measured wind speeds in an area outside the hive where the bumblebees were likely to forage. Studying these two datasets together allowed the team to determine the exact wind conditions during the bees’ foraging trips. The researchers found that these bumblebees experience a variety of wind environments, in terms of both wind speed itself and turbulence – characterised as the amount of variability in the wind speed over a 10 s period. However, the bees did not appear to adjust their foraging times to avoid windier or more turbulent conditions.
Next, the authors attached triangular markers to the backs of bumblebees from a different group and filmed them at 5000 frames s−1 flying in a wind tunnel that recreated some of the wind conditions that the bees had encountered previously: completely calm conditions and at two different wind speeds (1.5 and 3 ms−1), with and without turbulence. By tracking the markers on the bees’ bodies and the position of their wingtips in the videos, the team calculated the insects’ body orientation and wing movements throughout each trial, thus determining how the different conditions affected their flight.
The results revealed that bumblebees react and adapt to wind conditions in a number of ways, most obviously during turbulent conditions at the highest wind speed tested. Here, the bees appeared to roll to a greater degree, while this behaviour was not seen at lower wind speeds. The bees also beat their wings more often and with greater amplitude in these conditions. The authors suggest that this could be a way of increasing their control in changeable weather conditions; by reducing the time between wing strokes, the bees can respond more quickly to wind fluctuations when they occur and beating with a larger amplitude provides more power to their flight.
Though this study tested only a small subset of the wind conditions likely to be experienced by bumblebees, it provides a good insight into the strategies a bee can use to maintain stability in challenging weather. Work like this can also help to develop more effective control systems for bioinspired flying robots, allowing them to cope with more severe wind conditions. These robots could be useful in a variety of situations, carrying cameras to track wildlife poachers or aiding in police surveillance – helpful bee-inspired robots that will certainly cause a buzz!
