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Blue Riverjack   Blourivierjuffer   Flag of South Africa.svg

Family Platycnemididae Yakobson & Bianchi, 1905 Stream Damsels

Also known as Kubusi Streamjack or Blue Streamjack

Genus Metacnemis (Hagen, 1863)
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105 522 M valida Mzamba River 2016 11 12 13 36 59 4697 121 036 IMG 0751
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Short description:

Blue Riverjack (Kubusi Streamjack) , Metacnemis valida, Genus Metacnemis, Family Platycnemididae, medium sized, stout, strikingly primarily pale blue, with black stripes on thorax, and conspicuous black rings on abdomen.

Key identification features:

Male: 

  • Face dull black with a little brown. Labrum pale blue dull black with a little brown. Labrum pale blue with a central black spot. Anteclypeus grey. Postclypeus grey with two lateral streaks. Head above, black 121 036 IMG 0751 Neck pale blue with wide central black stripe.
  • Eyes dull pale blue, with some brown 121 026 IMG 0727
  • Thorax pale blue, strongly marked with narrow black stripes.105 518A M valida Mzamba River 2016 11 12 10 46 43 4089c
  • Wings clear with black veins. Pterostigmas light brown, almost square in shape.
  • Segments 2 to 6 with striking incomplete black rings against light blue background. Segment 7 with black stripe running along top. Segments 8 to 10 with fine black rings against light blue. Segments 8 and 9 with small black spots on either side. Superior appendages long, black. 105 518A M valida Mzamba River 2016 11 12 10 46 43 4089c

Female: 

  • Patterning similar to male. 
  • Eyes light brown above with distinct brown bn abobe ligh brown lower margin.
  • Black is replaces by brown black, pale blue not so vivid, except lower half of synthorax 105 519 M valida Mzamba River 2016 11 12 13 01 15 4508
  • Strong pale white/light brown stripe running across side of thorax;
  • Abdomen with brown saddle-like markings at hind margin od segment. S 9-10 distinctly bulbous 121 033 SB1 1266
  • Thorax has light brown white stripe wat lower thorac. Dorsal thorax greenish brown with darke brow dorsal carina stripew
  • Head, neck,thorax and segments 9 to 10 greenish brown above. 121 033 SB1 1266
Compared with other species:
  • Colouration, stout body, and its short pterostigmas make this species unmistakable
  • Only in the ECP, with few records from southern KZN
  • Spesbona angusta (Spesbona) is much lighter blue than, and much larger and more robust.
  • Mesocnemis singularis (Savanna Riverjack) has similar behaviour, but is all pale blue,distinctly pruinescent, and inhabits savanna rivers.
  • Blue bands on abdomen may be similar to Africallagma sapphirinum, (Sapphire Bluet)  109 504 20180115110804 01  
Distribution and habitat:
  • ECP, with few records from southern KZN. The species may be more abundant as previously assumed. More records requiered 
  • Rivers and streams in open landscapes, but sometimes shaded by gallery forest. Usually with rocks and probably often submerged roots and/or dead trunks or branches. Inferred to occur from 0 to 1400 m above sea level. 
Behaviour:

Powerful flyer that hawks out over fast flowing rivers or stream 

Further reading:
http://vmus.adu.org.za/vm_map_afr.php?&database=odonata&grid=2&outline=1&key=0&map=4&spp=661670 Books
A Guide to Dragonflies and Damselflies of South Africa   p. 56
Dragonflies and Damselflies of South Africa   p. 68
Dragonfly Biotic Index   p, 60
Websites
Tarboton 
A Visual Guide to the Damselflies and Dragonflies of South Africa
Odonata Atlas of Africa VMU Number 661670
Dragonflies & Damselflies Online 
The IUCN Red List of Threatened Species 
Endangered
Other Information:
Size Comparison Diagram 
Dragonflies, Damselflies
Morphology of a
Dragonfly,  Damselfly
Map of South Africa

 
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