There are several other similar sized white species may venture into ACT like Euproctis euthysana, E. melanosome, E. paradoxa, and male Trichiocercus sparshalli. Can these all be eliminated as possibles?
As far as I know the small white Euproctis species haven't been recorded in the ACT yet, although some are present in surrounding areas and might be here. The moth here is the wrong shape for T. sparshalli. Acyphas chionitis and semiochrea are hard to tell apart, and A. semiochrea appears to be the common ACT one.