Genus Anax Leach, 1815
emperors

Synonyms:

• scientific: Hemianax Selys, 1883

Type species: Anax imperator Leach, 1815

Introduction

Cosmopolitan genus with over 30 species, a third of them African. All are large (hindwing 43-65 mm) and powerful, A. tristis is among the world’s biggest dragonflies. Emperors may be seen patrolling endlessly over sunny waters, hunting termites at dusk, or lurking in vegetation far from water during the dry season. Most species breed in open standing waters with rich vegetation, such as ponds and marshes. Of these, A. imperator is most widespread and A. bangweuluensis and A. chloromelas are very localised, occurring in especially extensive and herbaceous marshes respectively. The widespread A. tristis and especially A. ephippiger favour seasonal habitats and thus are migratory. Four closely related species, however, breed in running water, males patrolling low over them: A. speratus and its western counterpart A. rutherfordi prefer more open streams, often in highlands, and A. congoliath forest streams and rivers; A. gladiator was recently discovered on high plateaus in Katanga, northern Zambia and northern Malawi. Males of all species are conspicuously coloured, with unmarked thorax (often deep green) and often bright blue, red or black (boldly spotted) abdomen. Hemianax ephippiger is treated in Anax. [Adapted from Dijkstra & Clausnitzer 2014]

Diagnosis

Male of genus is similar to other aeshnids by (a) triangles similar rather than dissimilar, in both wings, pointing outwards, both equally distant from arculus; (b) two Ax relatively thick and continuous across subcosta, others weaker and usually not aligned with subcostal cross-veins, rather than all being equally thick. However, Anax is set apart from the rest by (1) auricles absent rather than present; (2) IR3 not forked proximal to Pt; (3) R3 abruptly arched forward near distal end of Pt, rather than not or only weakly arched forward; (4) distal end of Rspl directed at point between Pt and wing tip, rather than directed at wing tip or posterior to it; (5) Hw tornus rounded, rather than angled; (6) anal triangle absent rather than present. [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

• 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. (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]
• 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].