I took a fly’s wing and put it under the microscope, I could see the veins that run through the wing. They seemed to stretch out the wing membrane, which was split into two layers, and make it stay rigid. There were two kinds of veins, one was thicker and ran from the body to the end of the wing, and the other kind was thinner and ran perpendicular to the other veins, making a sort of cell that would aid them in flying and keep the wing rigid.