According to The Complete Field Guide to Dragonflies of Australia;
Dragonflies are primitive insects, belonging to the order Odonata – a name which refers to the large teeth-like mandibles of both larva and adult. In Australia, the Odonata contains two suborders; the damselflies (Zygoptera) and the dragonflies proper (Epiproctophora or Anisoptera).
Damselflies are generally very slender insects, with forewings and hindwings similar in shape and venation and commonly held closed above the body. Damselfly larvae have external gills at the end of the abdomen. Dragonflies proper are stouter, stronger-flying insects. Their forewings and hindwings are more or less dissimilar in shape and venation and are commonly held spread out when they are at rest. Their larvae have internal rectal gills and the abdomen ends in an anal pyramid.
A large number of dragonfly and damselfly species are found only in Australia, some in relatively small regions. They have three development stages – egg, larva and adult – and both the egg and larval stage are aquatic. Westgate Park’s soaks, ponds, lagoons and lakes provide good habitat for dragonflies and the growth of plant species has brought a good supply of insects on which they aggressively prey.
Dragonflies and damselflies mostly fly during the day for feeding or mating. Otherwise, they rest on rocks or plants, usually near the edge of water bodies. Dragonfly species are generally ‘perchers’ (perching on vegetation and making short flights to catch prey) or ‘hawkers (continually chasing down flying insects). They can reach speeds of 50km/h in short bursts. They uniquely mate in a ‘wheel position’ in which the male grasps the female’s head or thorax while the female bends the tip of her abdomen up to meet the front of his. The sperm is transferred whilst allowing both to continue to fly. The female lays eggs in the water or inserts them into aquatic plants just under or above the water surface.
Many dragonflies and damselflies and their larvae are brightly coloured but colour can vary considerably according to age, sex, locality and habitat, making identification often difficult. The timing of adulthood is also widely variable though most can be seen in flight in summer.
A large dragonfly, the Blue-spotted Hawker is widespread in Australia and the only known species of its genus. It prefers still waters (lakes and ponds).
The Diplacodes genus ranges from Africa and Asia to Australia which has five of these tiny to small indigenous species. The Wandering and the Scarlet Perchers are the only ones to appear in Victoria. It is found in a wide range of still and sluggish waters.
Australian Emperor – Hermianax papuensis
Tau Emerald – Hermicordulia tau
Wandering Glider – Pantala flavescens
This species migrates to southern Australia on the winds of tropical low-pressure systems. It is a very fast flyer and rarely rests.
Aurora Bluetail – Ischnura aurora
Blue Ringtail – Austrolestes annulosus
Metallic Ringtail – Austrolestes cingulatus
Red and Blue Damsel – Xanthagrion erythroneurum
Slender Ringtail – Austrolestes analis
Wandering Ringtail – Austrolestes leda