Why flies are so hard to swat
Friday, 29 Aug 2008 00:09
Insect flight biomechanics expert Michael Dickinson said he can "finally answer" why flies are so hard to swat
Science In Focus
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An American scientist says he has solved the riddle of why flies are so hard to swat.
Insect flight biomechanics expert Michael Dickinson said he can "finally answer" journalists' questions going back many years.
The professor of bioengineering at the California Institute of Technology (Caltech) used high-resolution, high-speed digital imaging of fruit flies faced with a looming swatter.
He discovered that long before the fly leaps, its tiny brain calculates the location of the impending threat, comes up with an escape plan, and places its legs in an optimal position to hop out of the way in the opposite direction.
All of this action takes place within about 100 milliseconds after the fly first spots the swatter.
"This illustrates how rapidly the fly's brain can process sensory information into an appropriate motor response," Professor Dickinson said.
In one example, the videos showed that if the descending swatter comes from in front of the fly, the fly moves its middle legs forward and leans back, then raises and extends its legs to push off backward.
When the threat comes from the back, however, the fly - which has a nearly 360-degree field of view and can see behind itself - moves its middle legs a tiny bit backwards. With a threat from the side, the fly keeps its middle legs stationary, but leans its whole body in the opposite direction before it jumps.
For enthusiastic fly swatters, Prof Dickinson has the following advice: "It is best not to swat at the fly's starting position, but rather to aim a bit forward of that to anticipate where the fly is going to jump when it first sees your swatter."