We all know the bloodcurdling sound of a bloodsucking mosquito that has made its way into our general vicinity. It’s a distinct buzz that immediately gets your attention. A team of researchers has finally cracked exactly how mosquito’s fly and according to their findings, its flight “is generated in a manner unlike any previously described for a flying animal.”
GIF source: NGP Press
The four scientists have published their findings in the latest issue of Nature. Using eight high-speed cameras, the team filmed mosquito flight from a variety of angles and were able to analyse each beat of its wings. They were then able to apply their observations to fluid dynamics equations and trace the way the air moves around the wings. (Video at bottom.)
Two major features distinguish the mosquito from most other flying animals. Its wings beat at an extremely fast 700mhz and each beat comes in at less than 40 degrees. The researchers identify that as “less than half the smallest amplitude yet measured for any hovering animal.”
Ars Technica explains how the mosquito gets its lift:
The models found that lift is generated by three distinct mechanisms. The first, a leading edge vortex, is common in other insects…
During the downward sweep of the wing, a vortex of air is generated in front of the leading edge of the wing and then loops back over the wing. This creates an area of low pressure above the wing, providing some lift.But this only happens while the wing is sweeping downwards. Because of the mosquito’s short wing stroke, the wing doesn’t beat downwards for long. Something else must be going on.
One part of that something else is a trailing edge vortex. Normally, this vortex forms at the back edge of the wing and then moves off away from it (it’s said to detach from the wing). That means a trailing edge vortex doesn’t generate lift. But the mosquito wing stroke is such that, as soon as the animal stops its downward stroke and reverses its wing upwards, the wing runs into the trailing edge vortex. The vortex happily reattaches to the wing, providing it some lift. Here, the short wing stroke is an advantage, because the wing spends more time with a trailing edge vortex attached.
Where things really get unique is in the way the mosquito is able to generate lift by rotating its wings. As the wing finishes its upwards stroke, it rotates a small amount, starting at the body, and transitions into its downward path. A low-pressure area is created on top of the wing that provides a bit of lift, though it normally wouldn’t be enough to matter. But, the mosquito is able to maximise this extra lift.
Essentially, the mosquito is able to make its wing do two things at once by not rotating the whole wing. The rotation starts near the body and makes its way toward the tip. This means that the tip and the base of the wing are rotating so as to ensure that some part of it is always creating an area of lift with each beat of the wing. In this way, the mosquito is able to maximise the very fast strokes of its relatively short wings.
So, at this point, there are at least two things about the mosquito that are absolutely wild from an evolutionary perspective: It appears to fly like nothing else in nature and it doesn’t seem to have any real purpose in the overall ecosystem.
[Nature via Ars Technica]