Savanna Riverjack (Mesocnemis singularis)

View the above photo record (by Gregg Darling) in OdonataMAP here.

Find the Savanna Riverjack in the FBIS database (Freshwater Biodiversity Information System) here.

Family Platycnemididae

Mesocnemis singularisSAVANNA RIVERJACK

Identification

Medium sized

Length up to 44mm; Wingspan attains 62mm.

Robust for a damselfly, with a distinctive shape and posture. Males are easily recognised as there are no similar looking species in Southern Africa. Adult males are covered in pale blue-white pruinosity.

Females resemble those of Metacnemis valida (Blue Riverjack). The two are similar in size and shape and both are predominantly brown with darker markings. Metacnemis valida females have a prominent white diagonal band on the sides of the thorax. This is absent in Mesocnemis singularis. Additionally the two species are not known to co-occur.

Click here for more details on identification.

Mesocnemis singularis – Male
Mkuze River, KwaZulu-Natal
Photo by Ryan Tippett
Mesocnemis singularis – Female
Mkuze River, KwaZulu-Natal
Photo by Ryan Tippett

Habitat

Its natural habitats include open, rocky rivers and streams in savanna, bush or forest; as well as rocky shores of lakes. Mesocnemis singularis prefers fast flowing water, including broken and white water.

Habitat – Orange River, Near Keimoes, Northern Cape

Behaviour

Perches conspicuously near the water on rocks and overhanging or emergent twigs and stems.

Most active from October to May, but likely to fly all year round at some warmer sites (See Phenology below).

Distribution

This species is widespread in sub-Saharan Africa; it has been found in Angola, Botswana, Cameroon, the Democratic Republic of the Congo, Ivory Coast, Gabon, Ghana, Guinea, Kenya, Liberia, Malawi, Mozambique, Namibia, Nigeria, Sierra Leone, South Africa, Sudan, Tanzania, Togo, Uganda, Zambia, and Zimbabwe.

Below is a map showing the distribution of records for Savanna Riverjack in the OdonataMAP database as at February 2020.

The next map below is an imputed map, produced by an interpolation algorithm, which attempts to generate a full distribution map from the partial information in the map above. This map will be improved by the submission of records to the OdonataMAP section of the Virtual Museum.

Ultimately, we will produce a series of maps for all the odonata species in the region. The current algorithm is a new algorithm. The objective is mainly to produce “smoothed” maps that could go into a field guide for odonata. This basic version of the algorithm (as mapped above) does not make use of “explanatory variables” (e.g. altitude, terrain roughness, presence of freshwater — we will be producing maps that take these variables into account soon). Currently, it only makes use of the OdonataMAP records for the species being mapped, as well as all the other records of all other species. The basic maps are “optimistic” and will generally show ranges to be larger than what they probably are.

These maps use the data in the OdonataMAP section of the Virtual Museum, and also the database assembled by the previous JRS funded project, which was led by Professor Michael Samways and Dr KD Dijkstra.

Phenology

Dragonfly Atlas: Megan Loftie-Eaton, Sally Hofmeyr, Ryan Tippett & Les Underhill
Dragonfly Atlas: Megan Loftie-Eaton, Sally Hofmeyr, Ryan Tippett & Les Underhill
Megan Loftie-Eaton is our communications, social media and citizen science coordinator. Prior to her work for the BDI, she coordinated OdonataMAP, the Atlas of African Odonata. Sally Hofmeyr has many years' experience in the academic world, writing her own material and editing the work of others. Her academic background is in the natural sciences: her PhD and first postdoc in ornithology and environmental change (Animal Demography Unit, University of Cape Town). Ryan Tippett is an enthusiastic contributor to Citizen Science and has added many important and interesting records of fauna and flora. He has been a member of the VMU since 2014 and has currently submitted over 11000 records. He is also on the expert identification panel for the Odonata Map project. Prof Les Underhill has been Director of the Animal Demography Unit (ADU) at the University of Cape Town since it started in 1991. Although citizen science in biology is Les’s passion, his academic background is in mathematical statistics.