thanks for your answers, MrGuest, rayp, ratchet!
And thanks for the tip, ratchet, that's a great remark.
I planned the model for a normal enemy, but also for a boss.
So I think, I use this actual model for the boss and reduce it further for the normal enemys, later.
Skin is not finished, but here the state of work



edit: for the wings, I have copied the polygons and flipped the copy for the two-side-effekt. The wings are just brushes I used a brush in black and white for the structure and after this I selected the structure(selection from alpha-channel), increased the selection (1-2pixel) and filled it with two different color-Gradients (toolbox->blend in gimp).
For the question "have you assembled them to the model in MED ?" you have to excuse me, I didn't understand this question :-(
Normally, after all, I export the models as fbx and import them in MED. It worked with my last model, so I hope, it is working here again