Red admirals (kahukura) and yellow admirals are easy to tell apart when you see the upper surface of their wings (hint: red, yellow). However, sometimes they sit with their wings closed and then you've got to look a bit closer.

We've just added images to the Butterflies of New Zealand Guide that show you how to ID red and yellow admirals from their undersides. Here they are side-by-side highlighting the differences.

Yellow admiral: (note the yellow and rusty orange areas)

Red admiral (kahukura): (note the pinky-red and brown areas)