Overview
Coenagrionidae are small to large damselflies, often brightly coloured in males with either extensive areas of red or blue on the abdomen and/or thorax, or else multiple rings of colour separated by a dark ground colour. Females typically are much less colourful than the males: they may show a pale version of the male colour pattern or can be unicolourous yellow or grey. The family as a whole, with some notable exceptions, specialises in still and sluggish waters. It is cosmopolitan. Adults typically fly low over the water surface and perch on waterside plants. The larvae live amongst aquatic vegetation, and good, complex submerged vegetation is essential to their wellbeing. Few genera are endemic to Australia but about half of the 31 species are not found elsewhere.
The mainly tropical Agriocnemidinae includes some of the world's smallest Odonata in the large genus
Agriocnemis
(7 Australian spp.). The tiny, long-legged
Austrocnemis
(3 spp., north and east Australia, 1 extending to New Guinea) perch on floating leaves, and the much larger, dull red to black
Argiocnemis rubescens
is common on north and east coast streams. ??Amphicnemidinae (the blue and black
Archibasis mimetes
and the extremely slender, orange-red
Teinobasis rufithorax
) occur on tropical streams. The widespread, south-eastern
Coenagrion lyelli
, the very widespread
Austroagrion watsoni
(who's range does not quite extend to the more populated parts of Western Australia), and the ubiquitous
Ischnura heterostica
(found throughout Indonesia and the Pacific) are medium sized species with blue and black males, and often occur in sympatry. They can be distinguished on their blue colour markings: eyespots present in
I. heterosticta
, an eye bar in
A. watsoni
, and the blue on the abdomen more extensive in
C. lyelli
than in the other two species.
Females in subfamily Ischnurinae have a short mid-ventral spine on abdominal segment 8, before the ovipositor. In some extralimital species the females come in two colour forms, some taking the male colour throughout life. Tests on
I. heterosticta
in Australia have shown the male colour in females of this species to be a short-lived developmental stage immediately preceding sexual maturity. The tiny
Ischnura aurora
(males with a green thorax, a red abdomen, and blue rings around abdominal segments 8 and 9) is windborne across the Indo-Pacific, occurring both on oceanic islands and at desert waterholes. The females mate as soon as they emerge from the larva, before their first flight.
The subfamily Pseudagrioninae includes 2 monotypic genera, the common red, blue and black
Xanthagrion erythroneurum
which can form vast colonies on inland waters, and the large, blue and black, endemic south-eastern
Caliagrion billinghursti
, distinguished by the proximal position of vein Ac. The bright- to dull red
Ceriagrion aeruginosum
is common in the north.
Pseudagrion
(5 spp., north and east) includes
P. ignifer
(dark, pruinescent, the male with a bright orange face, on streams),
P. aureofrons
(the male spectacular, blue and black with a gold face and more gold on the thorax), and two species with a restricted northern distribution,
P. cingillum,
(males blue and black), and the bright blue
P. microcephalum
.
Agriocnemis
(7 spp.) and
Austrocnemis
(3 spp.) are tiny damselflies of the east and north, with wing length 12-13 mm and abdomen c18-23 mm: the most common is
Agriocnemis pygmaea
(green with a reddish mark at the tip of the abdomen).