Looking for ID for the larger/darker beetle, I think the smaller one may be Paropsisterna variicollis. Is this a different species or just a different colouration of the same species?
Both are Paropsisterna cloelia, which has both yellow and black variants. The name P. variicollis is now treated as a synonym of P. cloelia (see https://onlinelibrary.wiley.com/doi/abs/10.1111/aen.12476).
Thanks for the update Kim. Its seems ttis uodate might not have happened but for its introduction to WA and NZ. I wonder how many more species are in this position from DNA analysis. Remember Gonipterus.