The high-pitched whine of a hungry mosquito may be annoying but it also hides a scientific mystery. How do mosquitoes fly? Almost all insects can fly but for a long time, no-one could work out how. Aeroplanes were invented based on relatively simple aerodynamics. But when people tried to apply those theories to insects like bumblebees, they didn’t work. Compared to a plane, insects were too heavy for their tiny wings to keep them in the air. It took decades to start figuring out how insects fly but scientists did eventually discover their key trick… something known as a Leading Edge Vortex. As the air rushes past an insect’s wing, a tornado-like vortex forms on top at the very front edge. This swirl of rushing air decreases the pressure above the wing meaning that the insect gets a little extra lift to keep them up. But for mosquitoes, things aren’t quite as simple. Their wings flap extremely fast but only through a very shallow angle – only about 40 degrees – half that of a bee. That shallow movement shouldn’t be enough for them to fly using a Leading Edge Vortex alone. Solving this new mystery took eight slow motion cameras simultaneously recording a single flying mosquito from 8 different angles. This footage, here almost 700 times slower than its actual speed, was used to create a 3D model that could show exactly how the wing was moving. This enabled researchers to model how air flows over the wing in flight. As expected they saw a Leading Edge Vortex at the front of the wing. But they also saw something new: another vortex forming at the back edge of the wing… a Trailing Edge Vortex. As the back edge of the wing flips around it captures the swirling wake of the previous flap allowing it to recapture some of that energy. The formation of this second vortex, again on the upper surface of the wing, provides extra lift for the mosquito. While this may solve the problem of how mosquitoes fly it doesn’t answer the question of why they use this technique. Their high-speed, shallow-angle flapping doesn’t seem to be very power-efficient. The high frequency does make a noise though and that could be useful for things like attracting a mate. Whatever the reason, the mosquito’s trick could one day be stolen by humans, perhaps for use in the design of increasingly smaller flying machines. Let’s just hope they make a slightly less annoying sound.