This picture clearly shows three rows of pectinations in the antennae, diagnostic for genus Trictena, species probably atripalpis. They usually emerge en masse after a rainfall in mid autumn.
Simonsen in CSIRO Monographs on Australian Lepidoptera Vol 12 has moved all the Trictena (and Bordaia) to Abantiades, as the rami on the antennae which were considered tripectinate are actually unipectinate but triforked., and dna characters do not suggest separate genera.