Robust Skimmer (Orthetrum robustum)

The photo above (by Diana Russell) can be viewed in OdonataMAP here.

Find this species in the FBIS database (Freshwater Biodiversity Information System) here.

Family Libellulidae

Orthetrum robustum ROBUST SKIMMER

Identification

Large size

Length reaches 58mm; Wingspan attains 86mm.

The largest Orthetrum species. Key identification features include long yellow pterostigmas, with a dark leading edge and broad dark brown shoulder patches on a paler grey-brown thorax. The abdomen is pale pruinose blue. This pruinosity may spread onto the thorax with age. Fully pruinose males can be identified in the hand by the distinctive shape of the secondary genitalia.

Slightly larger than the Long Skimmer (Orthetrum trinacria), but that species is very dark blue overall and does not have a tapered waist.

Generally similar to most other Orthetrum species in terms of colouration, but can be seperated by its considerably larger size and broad dark brown shoulder patches.

Click here for more details on identification.

Orthetrum robustum – Male
Near Kosi Bay, KwaZulu-Natal
Photo by Ryan Tippett

Habitat

Associated with still-water habitats, particularly marshes, floodplains and the verges of pans and lakes. Favours marshy ground, rich in grasses and sedge and often with open patches of muddy or sandy substrate. Regularly found where the water-side grass cover has been grazed short or trampled by large animals like hippo, cattle and buffalo etc. Less frequent in areas of tall grass.

Habitat – Near Kosi Bay, KwaZulu-Natal
Photo by Ryan Tippett

Behaviour

Mostly sits low down over the ground or water. Hunts from a perch and frequently returns to the same spot. The flight is swift and powerful. Fairly confiding, but flies far once disturbed. Non-breeding individuals may be found away from the water in the surrounding woodlands where they hawk insects from bushes and trees.

Status and Conservation

Fairly common, but very localised. Increases in abundance, becoming more widespread locally during wet climatic cycles. During dry periods it retreats to larger, permanent water bodies. The IUCN Red List of Threatened Species, lists it as Near Threatened in South Africa, but as of Least Concern globally.

Only recorded from high quality habitats and is likely to be sensitive towards habitat degradation.

A large amount of the South African range of this species is protected within the iSimangaliso Wetland Park.

Distribution

Orthetrum robustum has a highly disjunct distribution in South-central and Southern Africa. There appear to be three main distribution centers. These are NE Zambia and neighboring Democratic Republic of the Congo. Northern Botswana and Namibia’s Caprivi Strip and finally the NE coastal plain of KwaZulu-Natal in South Africa and probably neighboring Southern Mozambique.

Restricted in South Africa to the coastal plain of NE-KwaZulu-Natal, reaching as far south as Richards Bay.

Below is a map showing the distribution of records for Robust Skimmer 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.

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.