These are really large damselflies but are usually referred to as demoiselles. The wings of males are covered with a patch of dense colour, smoky brown at first but becoming darker as the insect ages eventually becoming deep blue or purple. Some individuals have wings that are completely coloured and are considered by some to be a separate subspecies.

They prefer fast flowing clear streams with firm bottoms that they will patrol. They are happy to rest in either sun or shade, but only sunshine reveals the metallic beauty of their colouring.

As carnivores they feed on the other insects that frequent the stream banks. However, being relatively slow fliers, sometimes they fall prey themselves to the swifter and larger dragonflies.