Why are flies so hard to swat?

• Position: Bioengineering

Over the past two decades, Michael Dickinson has been interviewed by reporters hundreds of limes about his research on the biomechanics of insect flight. One question from the press always has dogged him--why are flies so hard to swat? "Now I can finally answer," indicates Dickinson, professor bioengineering at the California Institute of Technology, Pasadena.

"Using high-resolution, high-speed digital imaging of fruit flies (Drosophila melanogaster) faced with a looming swatter, Dickinson and' student Gwyneth Card have determined the secret to a fly's evasive maneuvering. Long before the fly leaps, its tiny brain calculates the location of the impending threat, comes up with an and places its legs in an optimal position to hop out of the way in the opposite direction. All of this action takes 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" Dickinson notes.

For example, the videos if the descending swatter--actually, a 14-centimeter-diameter black disk, dropping at a 50[degrees] angle toward a fly standing at the center of a small platform--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...