With some difficulty in most cases I think. Suggestion: The major slanting white mek near the wing tip is curved in D,scalariella whereas more straigt in D. aemuala ? On thet basis I would suggest D. scalariella in this case but such subtle differences are only going to be clear with good photographs so I would be reverting to Dialectica sp.(genus) in most cases.
Trying to add Dialectica sp.(genus), and got a CNM error 00-0e5de58ac32cd24e8ac213cb775157f8-e82c2ee452089740-00 I tried again with a 'space' between the the full-stop and the open-bracket. That worked OK.