JERRY BERGMAN To our chagrin, mosquitoes can and do fly, even though scientists have said they can’t. Our response is understandably, “I wish science was true in this case! No one likes mosquitoes.” Actually, scientists have just recently figured out how they are able to fly, and now realize that it involves a very complex designed system.
To our chagrin, mosquitoes can and do fly, even though scientists have said they can’t. Our response is understandably, “I wish science was true in this case! No one likes mosquitoes.” Actually, scientists have just recently figured out how they are able to fly, and now realize that it involves a very complex designed system. Solving this problem is important because it could have major applications to many other areas of technology, such as designs for micro-scale flying devices. An example is quadcopters, commonly called drones. To produce small micro-drones to fly into very small spaces looking for life, such as in buildings toppled by earthquakes, we need to understand how mosquitoes fly. This technology can then be used to produce micro-drones.
Many animals rely on the Bernoulli effect in order to be able to fly. The Bernoulli effect is the law that fluid pressure falls as the velocity of the fluid movement increases. Thus, the fluid pressure is inversely related to the velocity of the fluid. The Wright brothers discovered this effect by extensive experiments with birds and wind tunnels. They then used what they learned to build their first heavier-than-air flying machine powered by an onboard engine.
Airplane wings are shaped to force air to move faster over the top of the wing, causing the air pressure on the top of the wing to decrease. As a result, the pressure on the top of the wing is less than that on the bottom of the wing. The difference in pressure creates lift that literally pushes the airplane upward, at least enough to counter the effects of gravity.
This mechanism is used by not only airplanes, helicopters, and birds, but also by most insects – but not mosquitoes, surprisingly. Mosquitoes have small nearly flat planar wings, thus they produce very little lift. For this reason, how they were able to fly has for decades mystified entomologists (biologists who study insects).
Scientists solved the mystery of mosquito flight by using both super high-speed cameras and computer analysis.[i] They were then able to “understand the unique mechanisms the insect uses to stay airborne.”[ii] It is only now that science has been able to “explain how mosquitoes managed to flap their wings through such a short angle and still produce enough lift.”[iii] Mosquitoes move their wings around an arc of only about 40 degrees, lower than any other insect group.
Imaging a small creature with large antennae and legs that mask the view of its wings flapping at 800 beats per second, 4 times faster than many other insects of a similar size, was a great challenge. The solution was to use infra-red LEDs, a custom lighting rig, and eight cameras shooting at 10,000 frames per second. The eight cameras were set at difference angles to produce 3-dimensional pictures to help remove the blocking caused by the insects’ antennae and legs.
The researchers found that mosquitoes use three aerodynamic techniques to fly.[iv] The first is the leading edge vortex that is also used by most other insects. The second and third are a trailing edge vortex and rotational drag, both which, as far as is known, are novel to mosquitoes. Both of these mechanisms rely on subtle, but very precise, wing rotations. The trailing-edge vortex is a type of ‘wake capture’, that requires mosquitoes to align their wings with the air flows they created during the previous wingbeat. The result is they can exploit energy that would normally be lost. For this complex system to function requires not only the hardware, including the wing and neuromuscular design, but also the software, in this case the brain. A major problem for evolution is that, until the entire system was designed and built, mosquitoes could not fly. Consequently, they could not reach their food, which is plant nectar, and, in the case of female mosquitoes that are ready to breed and lay eggs, proteins and lipids—both of which are obtained in animal blood.
The common reason mosquitoes bite humans is because when their preferred food source, small mammals, is in short supply, humans are often a target. Mosquitoes become aware of the presence of humans by sensing carbon dioxide (CO2), and the average human exhales more CO2 than most all small mammals. Thus, humans make a bigger impression on a hungry female mosquito’s senses and an easier overall target. The human body also produces strong odor chemicals that, while unpleasant or undetectable to us, are very detectable to female mosquitoes.
The design of just the system that allows a small insect to fly is a wonder to behold. It took some of our brightest Oxford University scientists, and the latest technology, to unlock its secret. Nature awaits us with a seemingly endless supply of other wonders yet to be discovered.
[i] Richard J. Bomphrey, Toshiyuki Nakata, Nathan Phillips, Simon M. Walker. 2017. Smart wing rotation and trailing-edge vortices enable high frequency mosquito flight. Nature. 544(6):92-95.
[iii] Siciliano, 2017.