A succubus has the ability
Change Shape (Su): A succubus can assume the form of any Small or Medium humanoid.
It also has the natural ability to fly (50 ft, average maneuverability). Does it lose this when in a different form?
I imagine it does lose the ability, because (1) its ability to fly is based on using its wings, and (2) its ability alters the actual form of the succubus. But I can't back up either of these assumptions.
I'm playing D&D 3.5 (heavily house-ruled), but answers for D&D 3.0 or Pathfinder might still be enlightening. For what it's worth I'm the DM, so the final decision is mine in any case -- but I'd like to get it 'right' if possible.