An edit to give you some ideas on how to improve
-added a 0 luminance black for the eyes, on the wings and feet. Looks better to me with the extra colour
-limited use of dithering. I think less dithering works better on an insectoid as it makes the exoskeleton material come across better
-changed the lineart in a couple places to offset the mirroring effect. Added little subtle shading bits to do this as well.
-added selout and more AA.
-made the base hue more varied for each shade. You can see that it really does add to the image.
-added shading on to the legs. Looks much better than just leaving them flat if you ask me.
-on the top of hte mouth thing, you'll notice with the darker shades, showing wrinkle/ridges, that they curve to follow the mouth. this helps to bring out the shape of the mouth better so it doesn't look as flat like your version.
-lightsource was moved upwards
-I removed the ridges around his eyes. I tried a couple times to get something to work there, but with everything else done I decided to just screw it and post it as it was. Maybe you can get something working. The primary problem in your version is that the ridges are just dark lines, you weren't really paying enough attention to your lightsource and how that would make them look.
