I'm not a biologist but as far as I understand the motion of the wing surface for insect flight is out and down not just up+down.If you have solved this then one approach could be to use a CMOS SMT ( surface mount technology ) timer circuit driving an inductor loop that either attracts or repels the magnet and when not energized allows the wing to return to a neutral position. Neutral would necessarily at full extend or full contraction of the wing structure.
You can use Neodymium or Samarium-Cobalt magnets.
S08 pkg timer : NE555D
examples ( will give You an ides as to function and constraints) : **broken link removed**
Power source is a big factor in the design. Is the thing tethered? If free flight I would recommend the carapace to be constructed with a thin film amorphous solar cell. ( similar to the ones found on scientific calculators.
There's also another way to go , that being "muscle wires". It is an alloy wire that when current is applied the wire heats and contracts, something worth looking into.
Also You may want to check the robotics forum on this board for ideas.
Any more info would be helpful, force and weight calculations for one.