Genus Mesocnemis Karsch, 1891
true riverjacks

Type species: Mesocnemis singularis Karsch, 1891

Introduction

Endemic to Africa, five species are described, with one of the closely related genus Metacnemis in South Africa. All are fairly large (hindwing 19-27 mm), robust and pale brownish with limited black markings when teneral. The males become blue-eyed and entirely dark, extensively covered with thick whitish pruinosity, which is thinner on abdominal segments 3-7 only. Most species inhabit open rivers and larger streams, often sitting on sunny rocks. M. singularis and probably M. robusta also occur at (rocky) lakeshores. M. saralisa is only known from the Congo and its tributary the Lufira, M. dupuyi from the Gambia River, and M. tisi from the Sinoe River in Liberia. The latter is unusual for being very dark and living deeply shaded river sections with stilt roots. Identification relies on the shape of the ventral processes at the base of the cerci, which can be concealed by abdominal segment 10 and must often be viewed (partly) caudally. Due to this difficulty and the species’ superficial similarity, only two out of five were described before 1982, and more species are likely to be uncovered, particularly within M. singularis. [Adapted from Dijkstra & Clausnitzer 2014]

Diagnosis

Male of genus is similar to Agriocnemis by (a) head not very wide, about 2x as broad as deep; (b) quadrilaterals obliquely quadrangular, in Fw anterior border at most as long as distal border, often much shorter; (c) 3-5 cells between quadrilateral and subnode [2-5]. However, differs by (1) Ax1-2 converge posteriorly; (2) arculus proximal to Ax2, rather than at or distal from; (3) 3-5 cells between quadrilateral and subnode [2-5]; (4) Cux stands distal from origin of anal vein by about 3x its own length. [Adapted from Dijkstra & Clausnitzer 2014]

Map citation: Clausnitzer, V., K.-D.B. Dijkstra, R. Koch, J.-P. Boudot, W.R.T. Darwall, J. Kipping, B. Samraoui, M.J. Samways, J.P. Simaika & F. Suhling, 2012. Focus on African Freshwaters: hotspots of dragonfly diversity and conservation concern. Frontiers in Ecology and the Environment 10: 129-134.

References

• Legrand, J. (1982). Elattoneura pluotae spec. nov. (Protoneuridae) et Mesocnemis dupuyi spec. nov. (Platycnemididae), zygoptères noveaux du Sénégal. Odonatologica, 11, 153-158. [PDF file]
• Lempert, J. (1992). Mesocnemis tisi spec. nov., a new platycnemidid from Liberia, West Africa (Zygoptera: Platycnemididae). Odonatologica, 21, 495-497. [PDF file]
• Longfield, C. (1936). Studies on African Odonata, with synonymy and descriptions of new species and subspecies. Transactions Royal Entomological Society London, 85, 467-498. [PDF file]
• Schouteden, H. (1934). Annales Musee Congo belge Zoologie 3 Section 2, 3, 1-84. [PDF file]

Citation: Dijkstra, K.-D.B (editor). African Dragonflies and Damselflies Online. http://addo.adu.org.za/ [2024-11-15].