The moths are superficially similar. The native species D. scalariella was introduced to feed on Echium plantagineum as D. aemula does not feed on it. If there is no E. plantagineum locally, the moths are probably D. aemula. Tosio and Marianne wrote an article on how to distinguish them: https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1440-6055.1997.tb01427.x but I do not have access to it. Maybe until we have access to it, we should just refer these to 'Dialectica species'.
I can assure you there is plenty of E. plantagineum in Canberra, but whether its plentiful in Melba I'm not sure. I would be surprised if it were not present there. Thanks for the reference. I have access to it online. Excellent photos but of set specimens, of course. I have sent you via email a PDF copy of the paper.