Thursday, August 28, 2008

Why fleeing flies flummox flapping swatters

(Well, I like the headline, anyway!)

An article in the Daily Mail reveals why it's so difficult to swat a fly.

High-speed cameras showed that upon spotting a looming swatter, flies were able to plan and carry out an emergency take-off in under 200 milliseconds - or a fifth of a second.

A human eye takes around 300 to 400 milliseconds to blink.

The finding comes from a series of bizarre experiments carried out by American scientists using a 14cm black disc to mimic a fly swat.

Researchers dropped the disc on to fruit flies standing on a small platform and filmed what happened.

Long before making the leap, the fly calculates the location of the threat, works out its escape plan and positions its legs for a jump in the safest direction.

They found that if the disc approached from in front of the fly, the insect moved its middle legs forward and leaned back.

It then raised and extended its legs to push off backwards, the journal Current Biology reported.

When the threat came from behind, the fly moved its middle legs slightly backwards before leaping forwards.

Danger from one side caused the insect to keep its middle legs stationary, lean its whole body in the opposite direction, and then jump.

Professor Michael Dickinson, from the California Institute of Technology in Pasadena, said: ‘These movements are made very rapidly, within about 200 milliseconds, but within that time the animal determines where the threat is coming from and activates an appropriate set of movements to position its legs and wings.

‘This illustrates how rapidly the fly's brain can process sensory information into an appropriate motor response.’

Flies are helped by their compound eyes which have an almost 360 degree field of view, allowing them to look in front and behind at the same time.

The research, made possible by advances in super-high speed imaging, offered clues to the best strategy for swatting a fly.

‘It is best not to swat at the fly's starting position, but rather aim a bit forward of that to anticipate where the fly is going to jump when it first sees your swatter,’ said Prof Dickinson.

Flies are unable to register slow movement, making it possible to ‘creep up’ to a fly before delivering the killer blow, he added.

Now you know. As we used to say in darkest Africa, "Softlee, softlee, catchee monkey!"



Sevesteen said...

Best bare-handed method I've found is to bring your hands slowly to either side, then together about 4-6 inches above the fly. Clap--The fly will usually leap right into your hands.

Wash hands thoroughly after.

Michael M. Butler said...

It says the study was done on fruit flies. My experience with houseflies seems to indicate their strategies are somewhat different.