Taxon Attribute Profiles

Hemianax papuensis

Brachydiplax denticauda

Rhyothemis graphiptera

Indolestes obiri

Nososticta coelestina

Order ODONATA

Dragonflies and Damselflies

Introduction

Dragonflies and damselflies are large, strong flying insects which have fascinated watchers throughout time. They are among the best known insects, and because of their large size (usually 30-90 mm, but some species are known up to 150 mm), captivating behaviour, and ease of identification by the non-specialist, they have been referred to as "bird-watchers" insects. Many species are territorial, and they can display complex and intriguing behaviour. Dragonflies and damselflies are components of most riparian ecosystems. Both adult and larval stages are predaceous, and mostly prey upon other invertebrate species.

Taxonomy and Ecology

Synopsis of included taxa

The Odonata includes two suborders: Dragonflies (Anisoptera) and Damselflies (Zygoptera). Damselflies are smaller and more delicate, and have the forewing and hindwing similar in shape; dragonflies tend to be larger and stouter, and have the forewing and hindwing different in shape, with the base of the hindwing being wider than that of the forewing. In living specimens, the dragonflies generally rest with their wings extended, while the damselflies rest with wings folded together over their back. The larvae live underwater and breathe through gills. Damselfly larvae have the gills in the form of three long appendages extending from the tail end of their abdomen; dragonflies lack these appendages, and have internal rectal gills.

Dragonfly larvae

Notoaeschna sagittata

Synthemis macrostigma

Damselfly larvae

Austroargiolestes icteromelas

Austrolestes annulosus

The classification of Odonata is not settled. Watson & O'Farrell (1991) and Watson et al., (1991) list 11 families of damselflies and 6 families of dragonflies, while the ABIF Fauna List shows 12 families of damselflies and 18 families of dragonflies. Despite discrepancies concerning the number of families, authors do agree that there are just over 300 species of Odonata in Australia (302 in Watson & O'Farrell, 1991; 320 in ABIF).

General overviews of Australian Odonata, including morphology, biology and keys to the suborders and families are provided by Watson et al. (1991) and Watson & O'Farrell (1991).

Life Form

Dragonflies and damselflies are among the best known and recognized insects. Adults are generally large and elongate, with two pairs of large, membranous wings which have a dense network of veins. The compound eyes are quite large, and often occupy most of the head. Many species are quite beautiful, with bright metallic markings on the body, or various banded patterns on the wings. Adults are strong flyers, and are among the fastest of all insects. The larvae are aquatic, and have elongate, prehensile mouthparts which they use to capture their prey.

click to enlarge map

Distribution

Dragonflies and damselflies are widely distributed and common. Within Australia, they are most diverse in the tropical regions of north-eastern Queensland and Cape York. The aquatic habit of the larvae restricts reproduction to water sources, but lone adults may be found throughout Australia, often many kilometers from the nearest water source.

Habitat

Dragonflies and damselflies are tied to aquatic habitats. Although the adults are free living and capable of strong flight, the other life stages require a riparian habitat. Dragonfly and damselfly eggs are laid in water. Most commonly, the hovering females dip their abdomens into the water to deposit their eggs, and they can frequently be seen doing this, either singly or still coupled to the male. Larvae spend their entire life submerged in water, where they are predators on other small aquatic organisms. Various species can occupy most freshwater habitats, including waterfalls, torrents, streams, lakes, ponds, swamps, bogs and estuaries.

Cast skins of Hemicordulia tau

Adult emergence takes place when the larva crawls up out of the water onto a rock or branch, firmly grasps the substrate with its legs, and the adult emerges from the cast larval skin. Adults are strong flyers. Males are often territorial, and can be observed returning to a favourite perch where they observe their territory and are ready to fly out to capture food or guard against other males.

Status in Community

Both adults and larvae are predaceous, and will be responsible for removing numerous prey items during their life. Adults catch other invertebrates which they eat during flight. Larval prey items are generally other invertebrates, but larger species can take small fish and tadpoles.

Reproduction and Establishment

Reproduction

The Odonata are unusual in that the male has secondary genitalia at the base of the abdomen, to which he transfers sperm prior to mating. This produces a very characteristic coupling pose, where the male grasps the female behind the head with claspers at the end of his abdomen, and the female places the tip of her abdomen up to the base of the male abdomen. Elaborate courtship rituals are often precede mating.

Coenagrion lyelli

Eusynthemis virgula

Dispersability

Animals which inhabit standing, often temporary, water sources often display the ability for dispersal and migration over great distances. Adult dragonflies are strong fliers, and even though their larvae require water, lone adults are often seen great distances from water. This enables them to recolonize patches of standing water that are either unsuitable or non-existent during parts of the year.

Juvenile period

Larvae vary in habit, but all are aquatic. They can moult up to 15 times before they reach the final instar and are ready to emerge. All larvae are predaceous, and they are generally ambush predators which remain concealed in silt, or under rocks and plants, waiting for slow-moving prey. Odonata larvae are unusual in having hinged, prehensile mouthparts with strong teeth which they can shoot out to capture their prey.

Hydrology and Salinity

Salinity Tolerance

Kefford et al. (2003) reported Odonata to be more tolerant to salinity than many other aquatic macroinvertebrates; however, Bailey et al. (2002), Gooderham & Tsyrlin (2002) and Chessman (2003) showed a wide range of tolerance within the group. For example, on the SIGNAL 2 grades of 1-10 (1 being least sensitive and 10 being most sensitive), Odonata families ranged from 1 (Lestidae) to 10 (Austrocorduliidae) (Chessman, 2003).

Flooding Regimes

Alternating periods of flooding and drought could affect dragonfly and damselfly larvae, which need water for survival. The strong flying ability of adults will allow recolonization of aquatic habitats after periods of drought. Several species of Australian Odonata have larvae that are drought resistant, and can survive temporarily in an inactive state if free water is withdrawn (Watson, 1982).

Conservation Status

Hawking (1999) reviewed the conservation status of 314 Australian dragonflies and damselflies. Of the 314 known Australian species, 1 was listed as Critically Endangered, 12 Endangered, 24 Vulnerable, 39 Near Threatened, 84 Data Deficient, and the remaining 154 Least Concern.

The critically endangered species, Adams emerald dragonfly (Archaeophya adamsi), is one of Australia's rarest dragonflies, with only 5 adults having been captured. The species is known only from the greater Sydney region, and some remaining habitats are under threat from development.

Hawking (1999) pointed out three major concerns: 1) the large number of endangered species, 2) the large number of species which deserve priority conservation action; 3) the number of species where there is insufficient data to make a proper assessment.

Uses

Although there are no records of Aboriginal use of dragonflies or damselflies as food, it is not unlikely that certain species were eaten. It is well known that many insect species were eaten by Aborigines (Tindale, 1966); and the use of dragonflies and damselflies as food items in Asia and elsewhere in the world is well documented (Pemberton, 1995; Ramos-Elorduy, 1998; Menzel & D'Alusio, 1998).

Summary

Several authors have suggested that macroinvertebrates, including Odonata, can be effectively included in programs for monitoring water quality (Watson, 1982; Water and Rivers Commission, 1996; Chessman, 2003; Minnesota Pollution Control Agency, 2004). Due to the variability of response to environmental factors within the order, certain groups may be much more suitable as bioindicator species than others. The fact remains that they are large, easy to observe, and can be recognized by non-specialists, making them a very suitable group for a variety of monitoring purposes.

List of MDB Species

Table 1. Odonata recorded from the Murray Darling Basin

(Classification from Houston et al., 1999).

References