This is the grey, powdery caterpillar version of this species that I have occasionally seen on our acacias. It camouflages by getting itself really flat and melding well into the plant material when not active. It looks quite different to the more shiny green ones that I reared from eggs two years ago. Those couldn't flatten themselves as well and had less hair along the line of the feet. The underbody markings and two black stripes behind the head are the same in both.
They were all identified as P. nasuta as the adult moth looks the same. I'm looking at this colour variant again, as I didn't document it well last time I had one. I'm quite sure that both the caterpillar and adult moth were larger than the green form.