These are bud galls on Black Wattle, which I believe are caused by Dasineura rubiformis. The species is described in Kolesik, P., Adair, R.J., and Eick, G (2005) "Nine new species of Dasineura (Diptera: Cecidomyiidae) from flowers of Australian Acacia (Mimosaceae)", Systematic Entomology 30:454-479. You can find photos on the web from south africa and portugal since this species has been released for biological control of black wattle. It was found not to affect the growth of plantation trees, but drastically reduces seed production and therefore invasiveness. Species is fairly common in Woodlands Historic Park.