Through two-dimensional numerical simulations, the fluid dynamic consequences of varying the Reynolds number and the corresponding changes in the aerodynamic forces acting on the flapping wings are studied. The incompressible Navier-Stokes equations are discretized and solved on a non-body conforming Cartesian grid; the concept of immersed boundary method is made use of to impose the no-slip boundary condition on the surface of the wing. The objective of the present work is to examine whether the drag mechanism acting on the inclined stroke plane motions can explain the flight of tiny insects. Copyright © 2009 by the American Institute of Aeronautics and Astronautics, Inc.