T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Damselfly (Gossamer) Ischnura aurora

Kingdom: Animalia
Clade: Euarthropoda
Class: Insecta
Order: Odonata
Suborder: Zygoptera
Family: Coenagrionidae
Genus: Ischnura
Species: I. aurora
Binomial name: Ischnura aurora
Synonyms: Agrion aurora, Agrion spinicauda, Ischnura bhimtalensis,
Ischnura delicate, Ischnura rhodosoma
Common names: Aurora bluetail, Gossamer Damselfly, Golden dartlet, Wandering Bluetail

Ischnura aurora is a widely distributed species of damselfly from Pakistan, India, Asia, Australia and Pacific Islands including New Zealand. Wind currents are thought to have brought this species here. Since the 1960s it appears to have colonised the whole of the North Island. There are no reports of sightings in the South Island (2017). Their emergence occurs between October and March and few adults survive past mid-April. They can be seen flying and resting in vegetation. They inhabit the still waters of pools and swamps and the waters of sluggish rivers.

Ischnura aurora is the smallest of the NZ damselflies at >25 mm in length. It has a large head with very large compound eyes relative to the rest of their body. Each compound eye is composed of nearly 28,000 individual optical units (ommatidia), and together the eyes cover most of the head. More than 80% of their brain is devoted to analyzing visual information. By contrast, their antennae are tiny. Their mouths have been adapted for biting, making them efficient hunters. They have a prehensile labium, which can be extended forward from underneath the head faster than most prey can react, making their bite fatal to prey. The six legs are all located near the head and are seldom used for walking, but are more useful in catching prey and perching on vegetation to rest or lay eggs.
They have two pairs of elongated membranous wings that are similar in shape. They have a strong cross vein and many small veins in the wings that add strength and flexibility. The wings have hinges that enable them to fold together when resting. This feature of the wings is the key morphological feature distinguishing adult dragonflies from damselflies.

Ischnura aurora varies in appearance depending upon the sex. The male’s thorax is black with apple green stripes. The abdomen is a reddish-orange and the tail has a bright azure blue segment. The legs of males are green in colour. The abdomen’s seventh segment has an upper narrow and broad black mark. Segments 8-10 are entirely azure blue. The last segment is black. Young males have no blue abdominal tip. The legs are a pale greenish white and there is a vertical black stripe on the femur, just above the femur-tibia joint. 
The male’s large eyes are black above, olive green below fading to pale green beneath. There are two azure blue spots behind the eyes. The wings are transparent with a wing spot. The wing spots are different in the fore and hindwings. It is rose-red in forewings and uniform pale grey in hindwings.
The female’s thorax is a shiny black with two greenish stripes. The abdomen is yellow with black rings. The female’s eyes are brown above, green to pale green below. The legs are a pale greenish white and there is a vertical black stripe on the femur, just above the femur-tibia joint. The female’s abdomens, unlike the males, have no blue on the segments 8-10.

Female laying eggs. The eggs are cylindrical and are about 1 mm long.


An adult male.

Head and thorax of a female. The female’s eyes are brown above, green to pale green below.
 

Head and thorax of an adult male. They are black above, olive green below fading to pale green beneath


Thanks to Wikipedia for text and information
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