Genus Trithetrum Dijkstra & Pilgrim, 2007
- scientific: formerly placed in genus Sympetrum Newman, 1833
Type species: Sympetrum navasi Lacroix, 1921
This genus was recently described for two tropical African species that were formerly placed in Sympetrum but are genetically and morphologically very distinct. Males are medium-sized (hindwing 23-29 mm) and diagnostically uniform and unmarked. T. navasi is widespread and locally common along sunned grassy verges of rivers, ponds and lakes; T. congoense occurs with it from central DR Congo to south-eastern Gabon, favouring similar but smaller water bodies like small rivers, streams and pools. Both species may be mistaken for Trithemis, T. congoense especially recalling T. grouti, but have a different posture, sitting with abdomen held low and wings flat or slightly raised, often on leaves. [Adapted from Dijkstra & Clausnitzer 2014]
Male of genus is similar to Sympetrum by (a) size, Hw 23-35 mm; (b) all wings with 0 cell-doublings in radial planate [0-2]; (c) Pt never black-and-white and wings at most with dark tips or bases or with overall yellowish infusion; (d) Fw supratriangles without cross-veins; (e) Fw triangle of 2-3 cells, subtriangle of 3-6 cells; (f) Fw discoidal field of 3-4 rows at base; (g) 6½-8½ Ax in Fw; (h) arculus between Ax1-2, usually closest to Ax1; (i) if Abd ventrally red or orange, then dorsum similarly coloured. However, differs by (1) body parts uniform: thorax unmarked; frons without band; mid and hind femur all black; S1-10 unmarked; (2) venation blackish; (3) Fw discoidal field 5-8 cells wide on wing border. [Adapted from Dijkstra & Clausnitzer 2014; this diagnosis not yet verified by author]
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.
- Dijkstra, K.-D.B., and Pilgrim, E.M. (2007). Trithetrum, a new genus of African dragonflies formerly placed in Sympetrum (Odonata, Libellulidae). Journal of Afrotropical Zoology, 3, 77-81. [PDF file]
- Dijkstra, K.-D.B, and Clausnitzer, V. (2014). The Dragonflies and Damselflies of Eastern Africa: handbook for all Odonata from Sudan to Zimbabwe. Studies in Afrotropical Zoology, 298, 1-264.
Citation: Dijkstra, K.-D.B (editor). African Dragonflies and Damselflies Online. http://addo.adu.org.za/ [2018-06-23].