Genus Brachythemis Brauer, 1868
groundlings

Synonyms:

• scientific: Cacergates Kirby, 1889 [leucosticta]; Zonothrasys Karsch, 1890 [partitus = lacustris]; Termitophorba Förster, 1906 [rufina = lacustris]

Type species: Libellula contaminata Fabricius, 1793

Introduction

Besides four African species, there are single species in the Middle East and tropical Asia. All species favour exposed, standing or slow-flowing water, generally with bare banks, often perch on the ground, and are most active towards the end of the day. They are fairly small (hindwing 21-28 mm) and stocky, with pale pterostigmas darkened at their distal ends. The African species are easily separated into two pairs (coloration characters used in identification apply to mature males). Although B. lacustris does occur on lake beaches as its name suggests, it mostly inhabits rivers, often assembling in large groups on vegetation overhanging the water. Mature males are entirely red with the basal two-fifths of the wings deep amber. They may be confused with Trithemis kirbyi, but are much stockier with larger and paler pterostigmas. B. wilsoni is larger and has less uniform and extensive wing markings. Immature B. lacustris males with partly developed wing markings are similar, but B. wilsoni prefers marshy streams and backwaters. Records are scattered across the Sahel from northern Uganda and South Sudan to western Africa, with an isolated population in northern Botswana and north-eastern Namibia. B. leucosticta and B. impartita were only recently distinguished and overlap from Lake Victoria and Ethiopia to Senegal. Mature males of both have dark brown bodies and wing-bands. Tenerals have clear wings and yellowish bodies marked black. However, wing bands develop rapidly in B. impartita and unbanded males are thus rarely seen, unlike in B. leucosticta. Banding is also prevalent in B. impartita females, but uncommon in B. leucosticta. B. impartita may favour more sandy (vs. muddy) larval habitats and be on the wing more in the wet season, but definitive proof of ecological segregation is still lacking. Behaving rather like Cattle Egrets, both species follow larger mammals (including humans), flying low and catching disturbed insects. [Adapted from Dijkstra & Clausnitzer 2014]

Diagnosis

Male of genus is similar to Parazyxomma 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) subtriangle distinctly closed, of 1-3 cells; (d) anal loop closed before wing border; (e) 7½-9½ Ax in Fw, only rarely 10½; (f) wings with maturity usually either with much orange at base or with brown postnodal bands; (g) S4 with transverse ridge of similar strength as that on S3 and lateral carina S4. However, differs by (1) relatively smaller size, Hw 21-28 mm; (2) eyes not notably large, touching over distance about equal to length of vertex; (3) Fw triangle and subtriangle of 1-2 cells; (4) tip of anal loop does not reach posterior wing border. [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

• 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.
• Ris, F. (1921). The Odonata or Dragonflies of South Africa. Annals South African Museum, XVIII, 245-452. [PDF file]
• Pinhey, E.C.G. (1961). Dragonflies (Odonata) of Central Africa. Occasional Papers Rhodes-Livingstone Museum, 14, 1-97. [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/ [2024-10-30].