Which is the more annoying sound, a mosquito at night or a drone – well, any time?
The answer is it’s a tie, which makes any research with even a hope of dealing with both well worth pursuing.
Mechanical engineers at Johns Hopkins University in the US used computer modelling to study the aerodynamics and acoustics of the mosquito mating ritual and discovered how they use their wings to stay aloft and to simultaneously generate and direct a sound.
Unlike other insects their size, mozzies have adapted their anatomy and flight physiology to solve the “complex multifactorial problem” of trying to fly and flirt at the same time, says researcher Rajat Mittal.
“The wing tones as well as the aerodynamic forces for flight are highly directional and mosquitoes need to simultaneously control both for the successful completion of a mate-chase,” he and his colleagues write in the journal Bioinspiration and Biomimetics.
When the mood strikes, a male mosquito uses a high-frequency buzzing sound to attempt to connect with the low-frequency hum of a female.
To do so, the researchers found, it must flap its long, slender wings at high frequencies while also rotating them rapidly at the end of each stroke.
The quick rotation generates additional lift force to keep them aloft, while also helping direct the “wing tone” in a forward direction, which is important for chasing potential mates. They have to hear your chat-up line.
The speedy flapping and truncated range, or amplitude, is far faster and shorter than for winged insects of a similar size, such as fruit flies, Mittal says. That’s why mosquitoes have a wing tone buzz that is particularly annoying to humans.
The “long and slender wing is perfect for making sounds,” he says. “Fruit flies, which are similar in size to mosquitoes, have short and stubby wings. Furthermore, mosquitoes are flapping at much higher frequencies than fruit flies. There is a reason for this. Higher frequencies are better at producing sounds.”
The potential, the researchers say, is two-fold.
If we can find out ways to make sounds that can be used to interrupt the mating ritual, we might have an effective and non-toxic way to disrupt breeding and reduce mosquito populations.
“We continue to pursue that side of the research,” Mittal says. “At the right frequency the mosquitoes have a hard time flying and can’t complete their mating ritual.”
On a different tack, understanding the strategies and adaptations mosquitoes use to control their aero-acoustic noise could help in devising quieter rotors for drones.
Outdoor enthusiasts would be doubly grateful.
Nick Carne is the editor of Cosmos Online and editorial manager for The Royal Institution of Australia.
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