View the above photo record (by Jean Hirons) in OdonataMAP here.
Find the Blue Cascader in the FBIS database (Freshwater Biodiversity Information System) here.
Family Libellulidae
Zygonyx natalensis – BLUE CASCADER
(Martin, 1900)
Identification
Large size
Length up to 54mm; Wingspan reaches 86mm.
Most likely to be mistaken for one of the blue skimmers (Orthetrum spp.), which it resembles in general size, shape and colour. Zygonyx natalensis can be easily differentiated by the distinct gap in pruinosity along its abdomen, and by its metallic blue frons. In addition the Blue Cascader demonstrates very different behaviour to all of the skimmers.
Females most resemble both sexes of Zygonyx torridus (Ringed Cascader). They differ mostly in the size and shape of the yellow markings along the abdomen. Female Blue Cascaders show smaller, thinner yellow markings.
Click here for more details on identification.
Mkuze River, KwaZulu-Natal
Photo by Ryan Tippett
Habitat
Zygonyx natalensis inhabits rocky, fast flowing streams and rivers. It is particularly fond of river stretches with ‘white water’ where there are rapids, cascades and waterfalls. Occupies rivers in savanna, grassland and fynbos regions.
Photo by Sharon Stanton
Behaviour
Males are frequently seen patrolling a stretch of water or hovering low down over rapids and waterfalls. Frequently returns to hover at a favourite site after inspecting a length of river. Sometimes found away from water hunting over surrounding habitats. The flight is swift and powerful. Hunts on the wing and is not often seen perched. Females are not often seen and spend most of their time away from water.
Status and Conservation
Locally common. Listed as of Least Concern in the IUCN Red List of Threatened Species. This species make little use of man-made habitats other than artificial weirs that may simulate natural rapids and waterfalls. Reliant on healthy, flowing river systems.
Distribution
This species can be found over much of Sub-Saharan Africa, but is mostly recorded from Eastern and Southern Africa, ranging from Ethiopia down to the Western Cape in South Africa.
Widespread in the northern and eastern parts of South Africa where it is most common. It range continues south to the Eastern and Western Cape where it is more localised.
Below is a map showing the distribution of records for Blue Cascader 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.
Further Resources
Virtual Museum (OdonataMAP > Search VM > By Scientific or Common Name)
More common names: Blouklatertjie (Afrikaans)
Type Locality: Natal, South Africa.
Recommended citation format: Loftie Eaton. M; Hofmeyr S; Tippett RM; Underhill L. Blue Cascader Zygonyx natalensis. Biodiversity and Development Institute. Available online at https://thebdi.org/2020/02/20/blue-cascader-zygonyx-natalensis/
