I don't expect this image to help with an ID, obviously, but I'm including it for posterity, to show that these things on the underside of arrowwood leaves are in fact whitefly pupae:

I collected a leaf with some of these pupae maybe two weeks ago, and just looked in the vial this morning and found several adult whiteflies resting on the leaf. I'll hang on to the exuviae in case someone has a key that would be able to determine the species. My understanding is that adults aren't usually useful in identifying whiteflies.