After consultation I arrived at Trictena atripalpis of the Hepialidae family, also known as rain moth, bardee, bardy, bardi grub or waikerie. We found over 100 pupal cases in an area of approx 1000square meters. The larvae were most likely feeding on the roots of the eucalypts that grow at this site (mainly Eucalyptus melliodora, some E. bridgesiana).
There are many species of ghost moth that emerge after autumn rain in our district such as Abantiades spp,,Oxycanus spp., Trictena spp etc. I do not know if adult moths such as Trictena atripalpis can be identified from the shape of the spent pupal case but a moth expert may know.
I doubt whether identification to species is defensible without linking such a photo to a photo of he emerged and identified adult at the same locatiion and date. but I'd be happy to be shown differently.