That's a little ripper! doesn't look like a native plant it is on, were there any native plants nearby, in flower? Will try help with ID via Allen Sundholm.
This was on the bean vine in my vegie garden. Never seen anything like it before. I do have native plants further up the yard near the back of my house.
Stu and Alison - It's a Melobasis, and I'll call it M. purpurascens for now, although the taxonomy of this species and its relatives is confused and may change in the future.