It’s a little hard to identify without seeing all of the pattern however it’s either Castiarina livida or Castiarina flavopicta. I think livida is most likely from the date (flavopicta is usually later), colour (usually a greenish tinge to the background colour in flavopicta rather than blue), the flowers the beetle is on are normally associated with livida, and the part of the pattern that is visible is more likely to be livida.
I concur with MarkH - this is Castiarina livida. In this photo it is amongst (this species likes to bury in arse up) the flowers of is both adult host plant (general knowledge amongst aussie buprestid enthusiasts but apparently unpublished) and a larval host plant (by myself and R. de Keyzer, unpub.), being Ozothamus diosmifolius. Adults do occur on other adult host plants, su h as Leptospermum spp., but most often occur on Ozothamus diosmifolius. Cheers, Allen.