Julia Skimmer (Orthetrum julia)

The photo above (by Gerhard Diedericks) can be viewed in OdonataMAP here.

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

Family Libellulidae

Orthetrum julia JULIA SKIMMER

Identification

Medium sized

Length up to 57mm; Wingspan attains 74mm.

Most similar to Orthetrum stemmale (Bold Skimmer) and Orthetrum capicola (Cape Skimmer).

The most reliable way to differentiate between Orthetrum julia and Orthetrum stemmale is by examining the characteristic shapes of the males secondary genitalia. In addition the Julia Skimmer has black, rather than yellowish pterostigmas and all blackish wing venation. The Bold Skimmer has white subcostal Ax-veins. Furthermore Orthetrum julia shows a single cell row in the Rspl loop, whereas Orthetrum stemmale generally has two cell rows in the Rspl loop.

Julia and Cape skimmers have very similarly shaped secondary genitalia. They can, however, be told apart by other features. Orthetrum julia has blackish pterostigmas and white claspers, while Orthetrum capicola shows yellow-brown pterostigmas and dark claspers.

Click here for more details on identification.

Orthetrum julia – Male
iSimangaliso Wetland Park, KwaZulu-Natal
Photo by Ryan Tippett
Orthetrum julia – Old Male
iSimangaliso Wetland Park, KwaZulu-Natal
Photo by Ryan Tippett

Habitat

Inhabits shaded streams, rivers, pools and dams in dense forested or wooded areas. Inhabits both still and flowing waters. Regularly found away from water when not breeding.

Habitat – Ngome Forest, KwaZulu-Natal
Photo by Ryan Tippett

Behaviour

Breeding individuals found on waterside vegetation, but often found away from water in the surrounding forest or woodlands. Favours shady sites where it sits on exposed twigs in dappled light.

On the wing from September to May.

Status and Conservation

Common and widespread. Listed as of Least Concern in the IUCN Red List of Threatened Species.

Distribution

Widespread in the higher rainfall regions across Sub-Saharan Africa.

In South Africa it is found in the eastern half where it is most numerous in KwaZulu-Natal, Mpumalanga, Gauteng and Limpopo.

Below is a map showing the distribution of records for Julia 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.