The aerodynamics of mosquito flight have long been a mystery to scientists. Now high speed cameras have revealed the insects' long narrow wings and unusual flight behaviors, uncovering two new aerodynamic mechanisms unseen in any other insects, as well as raising new questions about the evolutionary functions of such strange flight actions.
To capture the mosquitoes in action the researchers created a miniature movie studio equipped with eight high-speed cameras recording at 10,000 frames per second. This allowed the team to examine the flapping actions of mosquito wings with an unprecedented level of detail.
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There are several features inherent to mosquitoes that make them unique in the field of flying insects. Firstly they have long, narrow wings that, when combined with an abnormally small stroke amplitude arc, result in a very strange flight action. A stroke amplitude arc is the angle of each individual wing sweep. In comparison, fruit flies have a stroke amplitude arc of almost four times that of mosquitos.
Equally unusual is the rate mosquitoes flap their wings. They are known to flap their wings 800 times per second, again nearly four times faster than any other insect of a comparable size.
The results from the high speed camera equipment allowed the research team to simulate the airflow surrounding the mosquito wings. They identified two new aerodynamic mechanisms that allow these unusual insects to fly: rotational drag and trailing-edge vortices.
Both of these mechanisms are the result of the specific way a mosquito wing rotates when it is pivoting at the end of each half-stroke. The research points to possible new innovations that could be developed in tiny scale flying technology.
The strangest part of the discovery is that while this explains why mosquitoes need to flap their wings so vigorously to maintain flight, it raises a whole new set of questions around the evolutionary benefit of this process. This is both an exquisitely refined and remarkably energy inefficient system.
The suspicion is that the buzzing sound caused by a mosquito's fast wing stroke also has a communicative function. "It's very likely to be acoustic communication," lead author of the study Richard Bomphrey told Quartz.
A 2014 study found that male mosquitoes could modulate the frequency of their flight tone and converge on a similar frequency with females when entering courtship processes. This suggests that the function of this strangely inefficient aerodynamic process could be underpinned by a yet to be identified form of mating communication.
Co-author of the study, Dr Simon Walker sees another outcome of this research as helping find ways to reduce the impact of many mosquito-borne diseases, "There is still much to learn from flying insects, the more we know about them, the better our chance of understanding their flight behavior, how they carry disease and eventually how to stop them from doing so."
The team recently published the results of its study in the journal Nature.
Take a look at the marvels of slow-motion mosquito flight in the video below.
Source: University of Oxford