Genus Trithemis Brauer, 1868
dropwings

Synonyms:

• scientific: Helothemis Karsch, 1890 [dorsalis]; Stoechia Kirby, 1898 [distanti = dorsalis]; Misthotus Kirby, 1905 [marshalli = dorsalis]; Congothemis Fraser, 1953 [longistyla]; Anectothemis Fraser, 1954 [apicalis]; Porpacithemis Fraser, 1954 [dubia]; Lokithemis Pinhey, 1956 [leakeyi]

Type species: Libellula aurora Burmeister, 1839

Introduction

These fairly small to fairly large (hindwing 21-35 mm) dragonflies are found at all kinds of freshwater habitats in Africa with over 40 species; two more are endemic to Madagascar and five to Asia. One-quarter of the species is predominantly red with maturity, appearing violet if pruinose, with striking orange or yellow wing patches. The others are largely dark, often (partly) blue or black pruinose with maturity, usually with reduced wings markings. Colours change markedly with maturation and preservation: red, violet or pruinose parts may be yellowish, brown or black in young or preserved specimens. Based on genetics and genitalia, three groups of closely related species are recognised, plus a number of species with less distinct relationships:

The basitincta-group contains dark species found at water with at least some flow. T. dejouxi and T. donaldsoni favour exposed, often quite fast and rocky, rivers and streams. T. aconita requires calm stretches and pools in streams that are both sheltered and sunny, e.g. within galleries in savanna or disturbed places in forest. It appears absent from the Congolese rainforest, where the closely related T. congolica is found along large rivers instead. They are replaced by T. nigra on Príncipe Island, which is notably smaller and does not become pruinose. T. africana, T. basitincta, T. bifida, T. integra, T. legrandi and T. tropicana are local at shaded streams, typically in forest, the last preferring swampy sites.

The dorsalis-group includes broad-bodied species, uniformly dark blue to black with maturity, with the exception of the red T. pluvialis. T. ellenbeckii, T. furva and T. pluvialis favour cool and often rather open streams, mostly in the highlands of eastern and southern Africa, where T. dorsalis prefers calmer and even standing sections. T. dichroa and T. pruinata replace their sister-species T. pluvialis and T. furva at sheltered (often forested) streams at lower altitudes in western and central Africa. The sister-species only overlap very locally, e.g. in northern Zambia and western Tanzania.

The stictica-group includes mostly slender species with the mature thorax coloured distinctly from abdomen, although the broader and dark-bodied T. grouti is reminiscent of the dorsalis-group. They favour marshy streams or similar habitats, e.g. channels in swamps, forest pools, oxbows or grassy river banks. T. stictica occurs in various open habitats and more in highlands than its relatives. T. aenea and T. nuptialis like streams in or near forest (the former especially with blackwater), as does T. grouti, although it favours more exposed and sluggish waters, like rivers and pools. The poorly known T. aequalis and T. palustris are associated with marshes from Katanga to northern Botswana; T. palustris (and the morphologically identical T. morrisoni) was first separated from T. stictica on genetic grounds. T. anomala and T. fumosa inhabit boggy or blackwater lakes and pools in forest-grassland mosaics.

Several fairly small (hindwing 21-30 mm) dark species with reduced wing venation were formerly placed in Anectothemis, Congothemis, Lokithemis and Porpacithemis. All are black with bold yellowish markings: T. apicalis, T. dubia, T. hinnula, T. leakeyi and T. osvaldae may develop pruinosity on thorax and/or abdomen (in latter two this is concentrated on middle of abdomen and notably white), but T. longistyla probably does not. Most records are from forested areas in the Lower Guinea and Congo Basin, but range from northern Zambia and northern DR Congo to western Africa. Adults are most commonly seen away from water, females being found relatively frequently. Possibly swamp forest and sluggish streams with thick detritus are the main breeding sites, over which males fly rapidly and furtively, rather like forest species of the basitincta-group. T. longistyla is the most aberrant Trithemis with its almost Neodythemis-like appearance. Males perch inside clumps of bare branches overhanging blackwater rivers.

The remaining species are mostly found at standing or slow-moving water. They include two aberrant dark species, plus all red ones except T. pluvialis. The black T. brydeni may be confused with the basitincta-group by secondary genitalia. It is scarce in large marshes in Botswana and Zambia. The very slender, dark blue T. hecate occurs almost throughout Africa, but is only numerous at seasonal marshes and lakes, e.g. at the Okavango where the similar T. aequalis is easily overlooked among it. The red species are conspicuous in open habitats and include two of the continent’s most familiar and wide-ranging dragonflies, T. annulata and T. arteriosa. T. kirbyi is similarly widespread, especially in dry and seasonal areas, favouring pools in rocky stream beds (or ornamental basins!). T. imitata and T. monardi occur at marshes and pools (these two species are so similar that it is uncertain whether they are distinct), mainly in savanna and woodland, while T. bredoi, T. kalula and T. werneri are local at (often larger) rivers. T. hartwigi is only known from open pools near forest in the Lower Guinea and a single photograph taken in eastern DR Congo. [Adapted from Dijkstra & Clausnitzer 2014]

Diagnosis

Male of genus is similar to Zygonyx 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) sectors of arculus in Fw always fused at base, separating well distal to arculus; (c) 8½-19½ Ax in Fw (‘½’ indicates often incomplete distal Ax); (d) arculus often closer to Ax2, sometimes even distal to it; (e) Fw discoidal field narrows terminally, number of rows just before end about equal to that at base, e.g. 3 and 4; (f) legs and often labium marked with black; (g) hook of hamule large, prominently apical; anterior lamina high, about as large as genital lobe; (h) S4 without transverse ridge, although colour pattern or scar-like seam may indicate its position, there is no ridge of similar magnitude as transverse ridge of S3 and lateral carina of S4. However, differs by (1) smaller size, Hw 21-35 mm; (2) 2 rows in radial planate; if 1 Hw usually under 30 mm; (3) posterior hook of tarsal claws at most quarter of size of anterior hook. [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.

References

• Pinhey, E. (1970). Monographic study of the genus Trithemis Brauer (Odonata: Libellulidae). Memoirs of the Entomological Society of Southern Africa, 11, 1-159. [PDF file]
• Clausnitzer, V. (2001). Notes on Trithemis bifida and T. donaldsoni (Odonata: Libellulidae). International Journal of Odonatology, 4, 179-189.
• Dijkstra, K.-D.B. (2007). The name-bearing types of Odonata held in the Natural History Museum of Zimbabwe, with systematic notes on Afrotropical taxa. Part 1: introduction and Anisoptera. International Journal of Odonatology, 10, 137-170. [PDF file]
• Ris, F. (1921). The Odonata or Dragonflies of South Africa. Annals South African Museum, XVIII, 245-452. [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]
• Pinhey, E.C.G. (1956). Some dragonflies of east and central Africa and a rarity from Mauritius. Occasional Papers Coryndon Memorial Museum, 4, 17-41. [PDF file]
• Pinhey, E.C.G. (1961). Dragonflies (Odonata) of Central Africa. Occasional Papers Rhodes-Livingstone Museum, 14, 1-97. [PDF file]
• Pinhey, E.C.G. (1961). Dragonflies (Odonata) of Central Africa. Occasional Papers Rhodes-Livingstone Museum, 14, 1-97. [PDF file]
• Barnard, K.H. (1937). Notes on dragon-flies (Odonata) of the S. W. Cape with descriptions of the nymphs and of new species. Annals South African Museum, 32, 169-260. [PDF file]
• Sjöstedt, Y. (1900). Odonaten aus Kamerun, West -Afrika. Beltrage Zur Kenntnis der insektenfauna von Kamerun. Binhang Kongliga Svenka Vetenskaps Akademiens Handlingar, 25, 1-62.
• 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]
• Schouteden, H. (1934). Annales Musee Congo belge Zoologie 3 Section 2, 3, 1-84. [PDF file]
• Fraser, F.C. (1954). Further notes and descriptions of new species of Libellulidae from tropical Africa. Revue Zoologie Botanique Africaines, 50, 252-268. [PDF file]
• Fraser, F.C. (1953). New genera and species of Libellulines from the Belgian Congo. Revue Zoologie Botanique Africaines, 48, 242-256. [PDF file]
• Kirby, W.F. (1900). Report on the Neuroptera Odonata collected by Mr E. E. Austen at Sierra Leone during August and September 1899. Annals Magazine Natural History, 6, 67-79. [PDF file]
• Sjöstedt, Y. (1909). Wissenschaftliche Ergebnisse der schwedischen zoologischen Expedition nach dem Kilimandjaro, dem Meru und den umgebenden Massaisteppen Deutsch-Ostafrikas 1905-1906 unter Leitung von Prof. Dr. Yngve Sjöstedt. 14. Pseudoneuroptera. Odonata, 14, 1-52.

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