Odonata: dragonflies and damselflies

Characteristics
These often brightly coloured, fast flying insects are well known and easily recognised. Dragonflies and damselflies are medium to large insects with body lengths ranging from 15-120 millimetres. They are often seen flying rapidly over streams and lakes, or through gardens at dusk, often following regular flight paths every day. Dragonflies and damselflies can be recognised by the following features:

Nannophya dalei

• Abdomen long and slender

Damselflies and dragonflies are very similar but can be separated by looking at their wings. In dragonflies the hind wings are slightly broader than the forewings and in damselflies both wings are more or less similar size. Wings are held horizontally to the body in dragonflies and vertically in damselflies when at rest.

The nymphs of these insects are aquatic and bear only a slight similarity to the adults. They are wingless and have a broader more flattened body shape. Dragonflies have gills within their body while damselflies have 3 leaf-like gills protruding from the tip of the abdomen (see below).

Life Cycle
Mating usually takes place on the wing and the male will guard the female as she flies along the water surface depositing her eggs. The nymph spend almost their entire life underwater and moult up to 15 times before they are ready to emerge.

When fully mature the final instar crawls out onto overhanging rocks or vegetation where they shed their last nymphal skin and emerge as an adult ready to hunt and mate.

Dragonfly nymphal shed skin

Development is dependant on the species and where they live. For most species development takes 1 to 2 years but some species that utilise temporary water bodies grow rapidly and develop into adults after a couple of months. Adults generally live for just a few weeks.

Feeding
Dragonflies and damselflies are carnivorous as both adults and nymphs. Nymphs feed on freshwater invertebrates catching them with specialised mouthparts that are able to spring forward and seize prey. Adults hunt by sight and prey on flying insects catching them on the wing with their legs.

Habitat
Dragonflies and damselflies are found all over Australia and although they need water to breed, individuals can be seen flying many kilometres from freshwater. Males tend to be territorial staying close by water to guard their hunting and mating grounds. They can often be observed perched on a favourite vantage point, usually a branch or rock protruding from the water or flying rapidly across their territory. When guarding their territory they will often fly rapidly after intruders chasing them away before returning to the same perch.

Females often roam further from water in search of prey. The nymphs are predominantly aquatic, although one species in known to inhabit wet leaf litter in northern Queensland. The nymphs of dragonflies and damselflies can be found in many aquatic habitats including either sluggish or fast running freshwater creeks, rivers, stream and lakes, and some species inhabit the more saline habitats of inland waters.