COVER A fruit fly tethered to a fine steel wire demonstrates the large stroke amplitude (160 degrees) and high stroke frequency (200 hertz) typical of small insects. Conventional steady-state aerodynamic theory fails to explain how insects generate enough force to remain airborne. Studies using robotic models of flapping wings have begun to uncover the unsteady mechanisms that insects use to fly and maneuver. [Image: Michael Springer/Gamma Liaison]
Copyright © 1999 by the American Association for the Advancement of Science.