''Gynacantha rosenbergi'' is a species of

dragonfly A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threate ...

in the family

Aeshnidae The Aeshnidae, also called aeshnids, hawkers, or darners, is a family of dragonflies. The family includes the largest dragonflies found in North America and Europe Europe is a large peninsula conventionally considered a continent in its o ...

, known as the grey duskhawker. It inhabits still waters and is found in New Guinea, Indonesia, through parts of northern Australia, as well as islands in the south

Pacific The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

Description

''Gynacantha rosenbergi'' is a large dragonfly with a wingspan of about 119 mm and overall length about 85 mm. It is strikingly coloured. Its

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...

is a dark rusty brown with greenish-yellow markings and its

thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...

is pale green. Its eyes are green tinged with yellow and, like other members of the

family, are large and joined together at the top. In front of its eyes the

frons Insect morphology is the study and description of the physical form of insects. The terminology used to describe insects is similar to that used for other arthropods due to their shared evolutionary history. Three physical features separate insec ...

has a dark marking that looks like the letter 'T' when viewed from above.

Abdomen

The abdomen is swollen where it joins the body, then forms a distinctive waist of about 2 mm at segment 3. This waist is about half the width of segment 2, the segment closer to the main body. Beyond the waist, the abdomen tapers to the end. The second segment of the abdomen on a male has light green auricles, miniature ear-like projections on each side. At the tip of their tails male dragonflies of the

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

'' Gynacantha'' have a distinctive pair of long, slim, anal appendages with fine hairs on their inner sides. These hold the female during mating. For ''Gynacantha rosenbergi'' the tips of the male anal appendages are curved slightly under and towards each other, which helps to distinguish it from other members of its genus.

Wings

Along the leading edge of the wing the

nodus This glossary of entomology describes terms used in the formal study of insect species by entomologists. A–C A synthetic chlorinated hydrocarbon insecticide, toxic to vertebrates. Though i ...

is about halfway and, towards the wing tip, the

pterostigma The pterostigma (plural: pterostigmata) is a group of specialized cells in the outer insect wing, wings of insects, which are often thickened or coloured, and thus stand out from other cells. It is particularly noticeable in dragonfly, dragonfli ...

is a creamy coloured patch about 5 mm long. The wings are translucent. The base of the hindwing is a diffusely golden colour which may extend to the nodus. Males have an angulated base to their hindwings, whereas females have a rounded base. The anal

triangle A triangle is a polygon with three Edge (geometry), edges and three Vertex (geometry), vertices. It is one of the basic shapes in geometry. A triangle with vertices ''A'', ''B'', and ''C'' is denoted \triangle ABC. In Euclidean geometry, an ...

, on the inboard edge of a male hindwing, is broad with three cells. The forewing

is stretched along the wing. The median space is clear without cross veins.

Similarities to other species

''Gynacantha rosenbergi'' is larger than ''

Gynacantha dobsoni ''Gynacantha dobsoni'' is a species of dragonfly in the family Aeshnidae, known as the lesser duskhawker. It inhabits ponds and swamps and is found in northern Australia. ''Gynacantha dobsoni'' is a large dull-coloured dragonfly with a constri ...

'', which in many ways appears quite similar.

Distribution

''Gynacantha rosenbergi'' is not commonly recorded. It has been found from the

Moluccas The Maluku Islands (; Indonesian: ''Kepulauan Maluku'') or the Moluccas () are an archipelago in the east of Indonesia. Tectonically they are located on the Halmahera Plate within the Molucca Sea Collision Zone. Geographically they are located eas ...

Vanuatu Vanuatu ( or ; ), officially the Republic of Vanuatu (french: link=no, République de Vanuatu; bi, Ripablik blong Vanuatu), is an island country located in the South Pacific Ocean. The archipelago, which is of volcanic origin, is east of no ...

and

New Caledonia ) , anthem = "" , image_map = New Caledonia on the globe (small islands magnified) (Polynesia centered).svg , map_alt = Location of New Caledonia , map_caption = Location of New Caledonia , mapsize = 290px , subdivision_type = Sovereign st ...

. In Australia it has been recorded from coastal north-east

Queensland ) , nickname = Sunshine State , image_map = Queensland in Australia.svg , map_caption = Location of Queensland in Australia , subdivision_type = Country , subdivision_name = Australia , established_title = Before federation , established_ ...

, north from about

Townsville Townsville is a city on the north-eastern coast of Queensland, Australia. With a population of 180,820 as of June 2018, it is the largest settlement in North Queensland; it is unofficially considered its capital. Estimated resident population, 3 ...

. It has been found on

Moa Island Moa Island, also called Banks Island, is an island of the Torres Strait Islands archipelago that is located north of Thursday Island in the Banks Channel of Torres Strait, Queensland, Australia. It is also a locality within the Torres Strait ...

Torres Strait The Torres Strait (), also known as Zenadh Kes, is a strait between Australia and the Melanesian island of New Guinea. It is wide at its narrowest extent. To the south is Cape York Peninsula, the northernmost extremity of the Australian mai ...

and on

Groote Eylandt Groote Eylandt ( Anindilyakwa: ''Ayangkidarrba'' meaning "island" ) is the largest island in the Gulf of Carpentaria and the fourth largest island in Australia. It was named by the explorer Abel Tasman in 1644 and is Dutch for "Large Island" in ...

in the

Gulf of Carpentaria The Gulf of Carpentaria (, ) is a large, shallow sea enclosed on three sides by northern Australia and bounded on the north by the eastern Arafura Sea (the body of water that lies between Australia and New Guinea). The northern boundary is ...

Behaviour

''Gynacantha rosenbergi'' inhabits still waters such as swamps and ponds. It rests in deep shade during the day and flies at dawn and dusk.

Gallery

Gynacantha rosenbergi 1782.jpg, Male grey duskhawker side view from below Gynacantha rosenbergi 1783.jpg, another view of the same dragonfly REcently emerged Grey Duskhawker imported from iNaturalist photo 261160418.jpg , Recently emerged female Gynacantha rosenbergi female wings (34895513002).jpg , Female wings Gynacantha rosenbergi male wings (34895521332).jpg , Male wings Gynacantha rosenbergi 0317.svg, Diagram of male abdominal parts Gynacantha rosenbergi curved anal tip dorsal K305406.jpg, Male anal appendages viewed from above. Note slightly curved tips. Australian Museum specimen K305406 Gynacantha rosenbergi curved anal tip lateral K305407.jpg, Male anal appendages viewed from the side. Note slightly curved tips. Australian Museum specimen K305407

References

{{Taxonbar, from=Q2153863 Aeshnidae Odonata of Australia Odonata of Oceania Insects of Australia Insects of New Guinea Insects of New Caledonia Taxa named by Johann Jakob Kaup Insects described in 1867