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Ask Fuzzy: The quick and the dead
Question: Why is it so hard to swat a fly?
Around this time of the year, flies get into your house and start buzzing around the room and batting against your windows. You chase one from room to room and with persistence, eventually flatten it against a window. Its parting gift is an oily smear, which gives a hint as to why they're so hard to swat.
A fly calculates an escape route within about 100 milliseconds of it spotting the incoming swat.Credit:iStockphoto
Their little bodies are packed with fats and proteins, which makes them a desirable snack, if you like that sort of thing. Not for humans perhaps, but for birds, spiders, and lizards they are an important source of food.
Understandably, the flies see it differently, and have evolved a set of highly effective defences.
Their size is one asset. A fly would weigh less than a gram, but your arm plus fly-swat is more like three kilograms. That's a lot more weight for you to mobilise, and you can't really change the direction once you've started the swing. Meanwhile your diminutive target needs only to propel - literally - its flyweight.
Surprisingly, the fly's tiny brain is also an advantage. You might be good at complex calculation, but that means firing up billions of neurons. Meanwhile, the fly brain calculates an escape route within about 100 milliseconds of it spotting the incoming swat. Using energy coiled in its legs, it can launch itself in an instant.
By comparison, you need about a second to spot an emergency and jam your foot on the car's brake.
After it launches, the fly switches into controlled flight, and demonstrates astounding aerodynamic abilities. They're so fast, researchers had to use three high-speed cameras, each taking 7,500 frames per second. Footage showed that fruit flies could flip and change direction within one or two wing beats, a feat well beyond the best fighter jets.
A flyswatter has a largish surface area, which pushes a strong puff of air ahead of it, giving the fly a handy push. A rolled up newspaper is similar, depending on how tightly bundled it is. (You could use today's Ask Fuzzy page once you've finished reading it.)
I find a slow swat is more effective than a high-speed swipe. Apart from taking away their wind assistance, they seem less attuned to the gradual squish. This would relate to how they detect movement from their extreme wide-angle compound eyes. It also negates the sensitive hairs on their bodies that are triggered by air movement.
Response by: Rod Taylor, Fuzzy Logic
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