Nearly every inflorescence in the mid-canopy on this Callistemon was covered in these beetles: the lower inflorescences were being ignored, and (as far as I could see) so was the top third of the canopy. Presumably this is due to subtle differences in nectar production within a canopy, and and phenological stage between shrubs. Another Callistemon adjacent was in flower but was not attracting these beetles. Beetle behaviour was like a feeding frenzy. I watched one beetle arrive on the individual flower then forcefully nose-dive down, and stay there.
One inflorescence has at least 10 individuals visible.