Dainty Swallowtail
Papilio anactus

Sometimes known as the Dingy Swallowtail, or Small Citrus butterfly (because the caterpillars feed on native and introduced Citrus plants, including grape-fruit, lemon, lime, mandarin and oranges).  This is an eastern states immigrant (early 1900’s) that has adapted to South Australia via the irrigated citrus orchards along the River Murray. The underside is similar to the upperside.

You can learn a lot more about this butterfly, on the research-quality website now managed by BCSA, (here)