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Why do insects like bees and flies buzz when flying? Does expending energy to make this sound help them?
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Guy Cox
ÌýSydney, New South Wales, Australia
When birds or insects fly, they displace air with their wings – that is how it works. Maybe sometime at night you have disturbed an owl and heard the flap of its large wings. This sound is a frequency way below hearing it as a note, but the principle is the same.
Hummingbirds are the only birds small enough to produce an audible note with their wings.
Bees don’t try to buzz, it is just the natural frequency of their wings.
Mike Follows
Sutton Coldfield, West Midlands, UK
The buzzing sound is usually caused by the displacement of air as insects flap their wings. Smaller wings can be moved faster, so smaller insects tend to buzz at a higher frequency. Producing even a loud sound doesn’t expend much energy.
As well as being a consequence of flight, buzzing can also be used to communicate. Insects such as mosquitoes change the frequency of their buzz to attract a mate.
Some moths use sound to evade predatory bats. For example, as the hindwings of Yponomeuta moths flap and bend, ridges on their surface rub against the air to create ultrasonic clicks warning bats that they aren’t very tasty.
Remarkably, buzzing is also responsible for pollination in 10 per cent of flowering plants. In a process called buzz pollination, also known as sonication, some solitary bees and bumblebees deliberately vibrate their flight muscles to match the resonant frequency of the anthers in the flowers they visit in order to dislodge the pollen. Some of this is consumed and some is inadvertently carried to the flowers they subsequently visit. Apparently, tomato plants can be buzz pollinated by touching the back of the flowers with an electric toothbrush and switching it on.
Mosquitoes fly and flirt at the same time. Male mosquitoes are smaller than females and buzz at a higher frequency (at about 600 hertz compared with around 400 Hz). When in close proximity, they try to match their buzzing frequency to signal to each other their potential as a mate. It appears that the female chooses a mate that is on her wavelength – literally.
Chris Daniel
Colwyn Bay, Conwy, UK
Flying insects buzz because their wings have to beat fast enough to generate lift, but this also produces a sound that we can hear, called the flight tone.
Insects can be identified by their characteristic frequencies, and even within a species, the male and female are distinct from one another.
A honeybee’s wings vibrate around 230 times a second, producing a frequency about three semitones below middle C. Other insects, many of which are flies, buzz at up to 2000 Hz, depending on their weight and the size of their wings. Mosquitoes, for example, flap their wings between 400 and 800 times per second, producing a higher pitch than bees or houseflies, but at a lower volume due to their smaller size. Hence they are often heard only in quiet rooms or when they get close to your head, attracted by your warmth and exhaled carbon dioxide.
Some insects buzz to communicate. Courting mosquitoes detect each other’s wing-beat frequency through their antennae and the male will respond by modulating its higher frequency to match that of the female. If this means arriving at a wing-beat that is incompatible with flight, the two insects will instead converge on a shared harmonic.
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