The wings of insects combine structural support and material economy because they are flat, braced surfaces.
“Insect wings provide yet another example of braced, flat surfaces–cylindrical cantilever beams (veins) support a thin membrane. A pound of fruit-fly wings laid end to end would stretch about 500 miles, a very low mass per unit length–a steel wire to go so far would have about the same diameter as a red blood cell. Yet in each second of flight the tip of a wing moves several meters and reverses direction four hundred times. Other paddles and fins are fairly flat as well, as are some feathers, the book gills of horseshoe crabs, and a scattering of other stiff structures. In all these cases, though, flatness suits functions other than support. From a mechanical viewpoint the flatness of these systems, however impressive, is perhaps best regarded as a necessary evil–and their designs incorporate features that offset their intrinsically low flexural stiffness.” (Vogel 2003:439)