Scientific name : Eurema smilax
Common name : Small grass yellow butterfly
The food plants for it are various Cassia and Senna. I have planted some Senna seeds but I think they have not sprouted, and otherwise we don't have any of these food plants for this butterfly. If the seeds don't sprout, I'll need to find some Cassia or Senna sp to plant. Cassia fistula is considered a weed/pest species in Brisbane and so it will need to be something else.
We also saw this butterfly in Boonah on the weekend - it seems to be quite common. The common name really does not do justice to such a lovely butterfly!