Are high-frequency flapping wings efficient and scalable at high Reynolds numbers? Is high-frequency flapping (similar to how dragonflies fly) an efficient lift production method at high Reynolds numbers? 

I have not seen anyone develop wing suits with high frequency flapping, is it efficient only at the insect scale? A few million years ago there used to exist dragonflies with wing spans around 70cm - correlating with the high oxygen content in the atmosphere at that time - so is this possible at larger wingspans too?

I'm thinking of something like the parademons in Justice League:
Some English University researchers studied the tiny helicopter Black Hornet versus Colibri-wings as efficiency. It was shown that rotating wings have LESS LOSS as the flapping ones because the latter must surpass the inertia of the wings at each flap. The insect wings have little weight and so small inertia.  So high-frequency flapping is only for small devices. What is better in the animal wings is the aerodynamic itself> Search "leading-edge vortex" on Google. Why animals have no rotating wings? >there is no rotating device in animals, because they must be fully articulated, by design... Only maple-seeds have a sort of autogyro.