Determination made on the basis of this observation - https://inaturalist.nz/observations/9675734 - see associated comments with that posting.

However, I confess the structures remind me more of Phyllocoptes coprosmae - are there Phyllocoptes that attack Melicope?

Common on the leaves of planted wharangi (Melicope ternata). Specimen collected but I have yet to examine it by microscope.