Dragonflies and damselflies

Dragonflies and damselflies are aquatic insects found in and around the freshwater streams of Australia. They are probably best known to fly fishing enthusiasts who tie flies to resemble both the flying adult and underwater nymphal life stages. Ecologically, they are an important dietary component of fishes in these streams, and their presence or absence in water bodies is used as a water quality indicator.

The aquatic nymphs (the immature stage of the life cycle) have cylindrical or somewhat flattened elongated bodies with large eyes. The hinged mouth parts can be shot rapidly forward to seize prey. Some of the larger nymphs are well known to anglers, who use them as bait and call them mud-eyes. The adults are vividly coloured strong fliers with large wings that actively hunt other insects during daylight hours.

Damselflies

Damselfly nymphs have a cylindrical abdomen with three leaf-like gills attached to the posterior end. They are found commonly in the still water of ponds and lakes among aquatic vegetation. They are distributed throughout Australia and are found in many other parts of the world. The nymphs capture a wide variety of small invertebrates.

Damselfly nymph
Photographers / Source: John Gooderham & Edward Tsyrlin

When adult damselflies are at rest, they hold their wings parallel to and above their abdomens. They are active predators and maintain territories near water bodies.

An adult damselfly
Photographers / Source: John Gooderham & Edward Tsyrlin

Dragonflies

Dragonfly nymphs are often elongated, with flattened mouth parts beneath the head. The abdomen ends in a pyramidal structure rather than external gills (see photo). The gills are internal. Water is pumped through the gills and can be expelled as a jet from the abdomen, enabling the nymph to move rapidly. These nymphs are found in both still and running water, sometimes on the underside of boulders and cobbles in swift-flowing streams. The nymphs are predatory.

Dragonfly nymph
Photographers / Source: John Gooderham & Edward Tsyrlin

The nymphs of both damselflies and dragonflies have aquatic life cycles that last for at least a few months, and more usually for a year. The adults are also quite long-lived and probably spend weeks to months in this phase of the life cycle in Victoria.

An adult dragonfly
Photographer: Alan Henderson / Source: Museum Victoria

The Dragonfly Life-cycle

A diagram showing the dragonfly life-cycle (anticlockwise from bottom): a nymph in the water, a nymph going through its final moult, a flying adult, a pair of mating adults and a female laying eggs.
Artist: Sharyn Madder / Source Museum Victoria

Adult dragonflies are generally more sturdily built than adult damselflies and when at rest hold their wings outstretched from their body. They are also active predators and are usually seen near water bodies.