This is a moth, not a butterfly. It is called the Zodiak Moth, a day-flying member of the family Uraniidae. It is large, being at least 10 cm across. The colours are quite individually variable. It was a welcome addition to the Photographic Walk and Talk we had a couple of weeks ago for the Friends of the Botanic Gardens in the Cairns Botanic Gardens.
As spectacular as the moth is, the caterpillar is even more striking. At different stages of development, the caterpillars look quite different. You might not even consider them as the same species. The caterpillars feed on a variety of plants in the family Euphorbiaceae. These plants are known for their toxic components. The white sticky sap is a phytotoxin. As a result the caterpillars that feed on these plants seem to be avoided by vertebrates. The moths themselves are slow-flying and are easily approached lending one to conclude that they are also avoided by birds and lizards.
This species is highly localised. Adults are regularly seen at the Cairns Botanic Gardens but seldom seen in our garden in Kuranda. It is assumed that the appropriate host plants are just not in our vicinity.