Investigation of unsteady flying insects is focused on low Reynolds number effect and aerodynamic properties. Interaction between flapping insect-wing and the air flow became one of important research field for development of micro air vehicle. The aim of the present work is to investigate the flow behavior of flapping wings of scarab beetle. The flapping motion and flow around wing are visualized with smoke-wire method and PIV. Tethered flight of the scarab beetle shows the motion with elastic

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... deformation of flapping wing. Measured flapping frequency is about 91 Hz and its frequency is higher than other beetles, dragonfly and butterfly. The flying beetle generates circulation of tip vortex and obtains lift by feathering motion, while the membrane wing adjusts to the angle of attack and the pitching angle under changes in aerodynamic force. Nomenclature AR = Aspect ratio, b 2 /s b = Wing span, m c = Chord length, m m = Mass, g R e = Reynolds number p = Pressure, Pa t = Time, sec s = Wing area, m 2 U = Velocity, m/sec u = Velocity component, m/sec u = Velocity of x axis, m/sec v = Velocity of y axis, m/sec = Angle of attack, degrees = Viscosity, Pa sec = Fluid density, kg/m 3 = Angular Velocity, rad/sec