Patrols sunny streams

A medium-sized dragonfly with a black abdomen, pinched near the base and fringed with orange crescent-shaped marks, the tips of which curve inward. Flies low over water, hovering for periods and conducting sorties mostly close to the bank but occasionally across open water. May be seen far from water above head height in gardens and parks. Compound eyes are made up of repeating units, the ommatidia, each of which functions as a separate visual receptor. Each ommatidium has a lens, a transparent crystalline cone, light-sensitive visual cells and pigment cells. The pigment cells ensure that only light entering the ommatidium parallel (or almost so) to its long axis reaches the visual cells and triggers nerve impulses. Thus each ommatidium is pointed at just a single area in space and contributes information about only one small area in the field of view. There may be thousands of ommatidia in a compound eye with their facets spread over most of the surface of a hemisphere. Eyes on mature males are bright green and wings are completely transparent and unmarked. Black pterostigma (those black panes on the outer edge of the wings, literally “wing marks”.) This species aggressively patrols the centres of sunny streams, ocassionally the edges, hovering often, then flying very fast, occasionally chasing off other dragonflies.

Male. Photo: Robert Whyte

This Emerald was patrolling a pond at the junction of the Fish and Enoggera Creeks in Walton Bridge Reserve. The frons (middle part of face) in this species have a metallic sheen. Photo: Robert Whyte

This photo shows the surface of the eye in magnified many times. Photo: Robert Whyte

At rest. Photo: Robert Whyte

Side on view of the Australian Emerald. Photo: Robert Whyte

Blue sheen. This view shows the metallic blue sheen on the frons quite dramatically, they are spectacular animals in closeup. This one was photographed at Walton Bridge Reserve on Sunday 13 April 2008. Photo: Robert Whyte