Hyrmine sexpunctata - Happy Little Stinker
I’m not convinced this is what I have but I think it’s a Catacanthus incarnatus. Aiyura Valley, Papua New Guinea.
Arp says: No it's not. See for updates in comments below!
New images of same species (presumably/probably):
Variant with red streaks:
Late instar nymph:
Hyrmine sexpunctata is a highly variable and colourful species of Stink bug (Pentatomidae) known from New Guinea and the surrounding islands, as well as from the east coast of Queensland, Australia.