This tiny, rugby-jerseyed, bristly creature (Trigonospila brevifacies) is a fly I don't think I've ever seen before. It is an Australian introduction, brought over to New Zealand to help control leafroller caterpillars. The female rests on leaves during her quest looking for her prey. When she finds one of the little leafroller caterpillars (that often curl up my orange tree leaves) she lays her eggs on it. Then it's the usual rather gross story: when the maggot hatches it eats the caterpillar. My Andrew Crowe book says that unfortunately we don't know the impact T. brevifacies is having on the harmless native leafroller moth.
You can see why this group of flies is called bristle flies. Maybe it's the insect equivalent of designer stubble. Except on females.