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Mosquitoes are some of the smallest and most dangerous animals in the world. Despite their diminutive size, they are one of the main vectors for some of the deadliest diseases, such as malaria, yellow fever and Zika virus. When compared to the humble buzzing of the bumble-bee, the whine of the mosquito is one attributed to irritation or illness. Now, it may also be attributed to some of the most incredible feats of aero-dynamics in the animal kingdom.
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A paper published in Nature explores a previously unexplainable phenomenon about the mosquito - how does it achieve the necessary lift for flight? Lead author Richard Bomfrey, a biomechanic from the Royal Veterinary College, as well as an interdisciplinary team of UK and Japanese scientists, have analysed the wing patterns of the mosquito in greater detail than ever before.
Using eight high speed cameras, as well as computer modelling and laser-based measurements, the team were able to capture the intricate details of a mosquito in flight.
The wing-stroke of the mosquito is significantly smaller than that of other insects, however it is substantially more effective.
Bomfrey and his colleagues found that a mosquito's wings beat at a frequency of over 700Hz – vastly superior to other flying insects such as the honey bee and common house fly. This produces the mosquito's distinctive whine when it flies, due to the rapid rate of movement. While the sweep of their wing is less than 40 degrees, the rapid rate of movement helps to lift them from the ground.
Most insects use a leading-edge vortex to create enough lift for flight. This occurs when a downward sweep of the wing creates a vortex of air that forms underneath – an area of low pressure that allows for enough momentum to initiate flight. Usually this only occurs when the wing sweeps downwards sufficiently, however since the mosquito's wing stroke is so short, this means that they require a different mechanism all together to lift them into the air.
Instead of a leading-edge vortex, the mosquito uses a trailing edge vortex. This means that the vortex forms at the edge of the wing, but moves away from the body as it forms – a process that would fail to generate lift in most animals. However, the mosquito can stop its downward strokes and reverse its wings, so as to catch more of this trailing vortex.
To do this, the mosquito can rotate its wings to reverse course from upwards to downwards. Usually, these rotations would occur too quickly in other insects to be able to produce any significant lift, however the mosquito can stretch out this process.
They slowly shift the axis of their wings and don't rotate the whole wing at once – taking every step of rotation at a gradual pace, until roughly 2/3 of the wing has changed position. This means that the wing is rotating for longer, thus creating a longer period for the vortex to adequately sustain lift. This creates a sense of aerodynamic equilibrium and is an incredible example of wing control.
No other animal in the world is known to do this - at least none that we know of so far. Further research into the flight of the mosquito could inspire new ideas about the process of flight as we know it, as well as help to understand one of the most intriguing and irritating insects in the world.
This article was originally published by WIRED UK
