Selectively import objects from Blender

I have a model in Blender which consists of a hierarchy of "real" objects and "dummy" objects. For example:

• Armature

  • Biped Mesh

• Rigging Control

  • Left Hand Control

  • Face Control

    • Eye Control

    • etc

In the example, everything in the Rigging Control hierarchy are empty objects that act as targets for IK, animation control, etc. I would like to exclude these objects from Unity so that they do not import. Is there a way to do this?

(I know I can delete the objects manually when I instantiate a copy in Unity's scene editor, but this breaks the prefab connection. As I am still in the art tweaking phase, I would prefer not to do that.)