On citrus? Could be one of the Swallowtails - the lowest caterpillar is one of the Swallowtails. Which one I don't know but it looks like 'bird droppings' as does the second one up. The top one is anyone's guess. Can you pick it off with its branch and take it inside for a clearer photo? Do you have Create More Butterflies? That's the book I leafed through to see if I could find anything similar. Also the site Brisbane Insects could be worth a whirl.
There is not much left on this plant, they have defoliated it almost, it is a pineapple orange tree. I think the top one is a Glasswing butterfly. Unfortunately I don't have a good book on the caterpillar side of butterflies.
The Glass wing larva pic in my book is kinda light tan with black stand-up hairs; there may be other colour variations not illustrated. Glass wing larva illustrated here.
It has developed orange spots on the side, and we had a glasswing flying around here for a few days so it is highly likely.