Blue Riverjack, Metacnemis valida, Blourivierjuffer   Flag of South Africa.svg    Species only found in Africa

121 029 Blue Riverjack Metacnemis valida IMG 0095

Blue Riverjack Metacnemis valida121 033 SB1 1266

121 031 SM7 0308 Blue Riverjack Metacnemis valida

Short description:

Blue Riverjack, Metacnemis valida, Blourivierjuffer is medium sized, stout, strikingly primarily pale blue, with black stripes on thorax, and conspicuous black rings on abdomen.

Also known as Kubusi Streamjack or Blue Streamjack

Family Platycnemididae      (Yakobson & Bianchi, 1905 Stream Damsels)
More Images:

Blue Riverjack Metacnemis valida105 522 M Mzamba River 2016 11 12 13 36 59 4697Image Galley

121 036 IMG 0751 Metacnemis valida Blue Riverjack Male

 

 

 

 

 

 

 

 

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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 Blue Riverjack Metacnemis valida

Female:

  • Patterning similar to male. 
  • Eyes light brown above with distinct brown light brown lower margin.
  • Black is replaced 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 of segment. S 9-10 distinctly bulbous 121 033 SB1 1266
  • Thorax has light brown white stripe wat lower thorax. Dorsal thorax greenish brown with dark brow dorsal carina stripe
  • Head, neck,thorax and segments 9 to 10 greenish brown above. 121 033 SB1 1266
Habitat:
  • 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 

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

 distribution Map May 2020

 

 

 

 

 

 

 

 

 

South Africa:

  • Endemic to South Africa. 
  • ECP, with few records from southern KZN. The species may be more abundant as previously assumed More records required 
Further reading:

Websites
Odonata Atlas of Africa VMU Number 661670
Dragonflies & Damselflies Online 
The IUCN Red List of Threatened Species Endangered
A Visual Guide to the Damselflies and Dragonflies of South Africa

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