The larvae of this fly form galls in the flowers of daisies in the genus Senecio (Fire Weed), of which there are several species in the park. On the Galls page there is a photo of a flower gall on Cotton Fireweed. The flies in the photo above were seen on a Rough Fireweed.
Classification
from Australian Faunal Directory
Order Diptera - Flies, 8955 named species in Australia at Nov. 2021
Division Cyclorrhapha - Flies having Short Antennae with a Bristle or Arista
Family Tephritidae - Fruit Flies, 293 named species in Australia
Genus Sphenella
Species Sphenella ruficeps
Reference
DE Hardy and RA I Drew (1996) Revision of the Australian Tephritini (Diptera : Tephritidae). Invertebrate Taxonomy 10(2) pages 213 - 405.