Genus Tholymis Hagen, 1867
Type species: Libellula tillarga Fabricius, 1798
Both species of the genus are common and widespread, with one species each in the New and Old World tropics. T. tillarga is a fairly large (hindwing 34-39 mm) big-eyed species, entirely pale brown turning red with maturity, with distinctive hindwing markings: a large brown patch between the triangle and node is mirrored by a patch of white pruinosity on the proximal side of the node. Hanging in dense vegetation during the day, it is active at dawn, dusk and before rain, flying erratically over standing water, the milky-white wing markings standing out in near-darkness. Eggs are deposited in flight on a submerged substrate (usually a leaf): typically the female turns around before each downward swoop. The species owes its vernacular name to this behaviour. [Adapted from Dijkstra & Clausnitzer 2014]
Male of genus is similar to Zyxomma by (a) hindlobe of prothorax small, roughly semicircular and widest at base (dorsal view), apex often pressed downwards (lateral view), its border with short hairs and at most a few longer hairs; (b) Pt in both wings of similar size; (c) Fw triangle points approximately to distal apex of Hw triangle; (d) subtriangle distinctly closed, of 1-3 cells; (e) Fw anal field at arculus of 2 rows; (f) anal loop usually open on wing border; (g) wing markings usually less extensive or intense, or stronger on Hw, and never with brown postnodal bands; (h) S4 with transverse ridge of similar strength as that on S3 and lateral carina S4. However, differs by (1) 9½-10½ Ax in Fw [9½-11½]; (2) bridge spaces with 1 (rather than 2-3) cross-vein; (3) Hw with brown marking touching node on proximal side, usually with white marking (visible against dark background) on distal side; (4) 2 cell-rows in radial planate; (5) Abd shorter than Hw, S4 parallel-sided. [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 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.
- Pinhey, E.C.G. (1961). Dragonflies (Odonata) of Central Africa. Occasional Papers Rhodes-Livingstone Museum, 14, 1-97. [PDF file]
- Fraser, F.C. (1955). Odonata. Exploration Parc National Upemba. Mission G F de Witte, 38, 1-34. [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/ [2019-01-17].