This is Selagis formosa. It has previously been considered a sub species of S. caloptera by some authors however Dr Fritz Brechtel, who is working on the revision of the genus Selagis, has advised that this is a good species and is distinct from the Selagis caloptera that you find say around Sydney. I have viewed the types of S. formosa and S. caloptera and they are quite distinctive. I have collected S. formosa in the Hunter Valley and north into central Queensland while S. caloptera I have found as far north as Byfield in Queensland.
It is wonderful that, as anticipated, Fritz will recognise this as a valid species, a status that has long been suspected. I note that in his 1929 check list H.J. Carter treated it as a mere 'variety', which has no taxonomic status (read further below as to why he might have thought such). Selagis formosa occurs around Sydney where I have taken it at Picton, at Currency Creek which is just north of Wilberforce, and with R. de Keyzer near the bridge where the Putty Road crosses the Colo River. I have also taken it near both Currarong and Huskisson on the NSW south coast. In the Atlas of Living Australia records there is a specimen that is clearly Selagis formosa from Brogo, on the far south coast of NSW (see: https://biocache.ala.org.au/occurrences/fd6f39a9-64aa-44ed-96f4-3cd6077e47d6), and another photographed in December 2024 from nearby in far southern NSW at Black Range (see: https://biocache.ala.org.au/occurrences/9a645588-6567-4cc8-b4af-9e146c37b28f) (I have been in touch with the observer). Selagis formosa occurs in Victoria at Lederberg just north of Melbourne, where it has been taken by Martin Lagerwey and whose pic of it will be in the proposed book I am the lead author of on the jewel beetles of Victoria. Selagis formosa also occurs at Upper Yarra Reserve in the mountains NE of Melbourne (see: https://www.inaturalist.org/observations/35365682). Looking at the photos in those online records they are clearly all 'formosa'. However, amongst the caloptera specimens in the entomology collection held by Museums Victoria there are some specimens that appear to be intergrades between caloptera and formosa, which may have caused H.J. Carter to assume that Gestro's later-described species formosa was just a variety of caloptera. I have not had a look at those specimens, I have been sent photographs only, and not all that clear, but I admit they do look rather like intergrades. Both typical formosa and caloptera occur around Melbourne. Perhaps Fritz and / or MarkH might want to take a close look at the Museum Victoria specimens (sitting in the unit trays for caloptera) to determine once and for all what they are, either caloptera, or formosa, or what. Cheers, Allen M. Sundholm.