Identification to species relies on antennae shape, colour and size and a look at the genitalia which is out of the question here. Wing pattern is not very reliable and varies a lot. I think O.silvanus (yelow), O. rufescens (shape) and O. antipoda (yellow) can be probably ruled out on antennae features (based on the MoV guidelines). But i think O. dirempta and O. australis remain possibilities. However, according to John Neilson (pers. comm) O. australis has not been recorded in the ACT and records on the ALA and MoV bears this out. However O. australis has been recorded in coastal localities east of here at this latitude.