Of all things, pumpkin seeds.
In a conversation I had with a woman who owns a large commercial garden/nursery, all organic, she mentioned pumpkin seeds. I assume raw/dried ones are okay (not smoked, of course).
You can also put diatomaceous earth (food grade, not swimming pool) in their food (when they are super hungry, doesn't taste too good but perfectly edible) and where they hang out. This works better with fleas. http://healthwyze.org/index.php/com...eworming-and-eliminating-fleas-naturally.html