The unique aerodynamic mechanisms underlying mosquito flight are described in a paper published online in Nature this week.
Mosquitoes have long, thin wings that beat rapidly for their size (at a frequency of around 800 Hz), with shallow strokes that are smaller than in any other insect group. The entire angular sweep of the mosquito wing is around 40 degrees, less than half that of the honey bee, prompting speculation over how mosquitoes manage to fly at all.
Richard Bomphrey and colleagues show that, in addition to generating lift by leading-edge vortices (a mechanism used by most insects, whereby ‘bubbles’ of low pressure are created along the leading edge of the wing), mosquitoes use two additional aerodynamic features: so-called trailing-edge vortices, and a type of lift mechanism generated by the rotation of the wing. Whereas other insects produce the majority of weight support during the translational phases of their down- and up-strokes, the unique wing shape and motion of mosquitoes means that their weight is most supported during the brief periods of wing rotation at the end of each half-stroke. This, in turn, gives rise to vortices on the wing’s trailing edge caused by a form of wake capture (a phenomenon whereby the insect gains extra lift by recapturing energy lost in the previous stroke).
It remains uncertain why mosquitoes have evolved to operate outside the usual bounds of kinematic patterns used by other insects. However, the authors suggest that the greater inertial power required by high-frequency flapping may be compensated for by other selective advantages, possibly in the domain of acoustic communication.