Spesbona (Spesbona angusta)

Cover photo of Spesbona by Gregg Darling.

Find the Ceres Streamjack in the FBIS database (Freshwater Biodiversity Information System) here.

Family Platycnemididae

Identification

Very Small Size

Length up to 30mm; Wingspan reaches 38mm.

Spesbona angusta is the only member of its genus. The Spesbona is unique in that both sexes are photochromatic. This means that their colour and saturation change in response to light exposure and the resultant increase in body temperature.

The postocular markings on the head, the broad black band on top of the thorax, and most of the abdomen (except the last 3 abdominal segments) are always black. The rest of the head, thorax sides and the terminal segments of the abdomen vary in colour, shifting from blackish to pale grey, then blue, and finally vivid mauve or purple when in full sun.

The sexes are similar in general size and appearance. Females are more robust and less colourful than males and have browner eyes and slightly smoky wings. Males have elongate claspers on segment 10, which females lack.

Male Spesbonas are most likely to be mistaken for the Male Mauve Bluet (Proischnura polychromatica). Both show violet and black colouration, but the Spesbona is larger and more robust. The head of the Spesbona is violet with black postocular markings, while the head of the Mauve Bluet is black with purple postocular markings.

Click here for more details on identification.

Habitat

The Spesbona inhabits small, still-water pools and marshy places connected to streams and meandering rivers. It is sometimes also found along shallow, slow-moving sections of streams. The Spesbona favours sites with an abundance of overhanging grasses or sedge, and with fynbos plants along the banks. It is partial to pools with emergent and floating vegetation, especially Common Waterblommetjie (Aponogeton distachyos) and sometimes also waterlilies Nymphaea and/or Nymphoides spp.

The Spesbona is found mainly at altitudes of around 60 to 400m above sea level.

Behaviour

The Spesbona typically sits lengthwise along a grass or reed stem, usually low down close to the water. They may also perch on a low rock or on floating leaves. The Spesbona is relatively confiding and often reluctant to move. When disturbed, they fly low over the water to a new perch. Males and females are frequently found together, and non-breeding individuals can be found in dry grass a short distance from the water.

The Spesbona is on the wing from late August until the end of December. It is mainly an early-season species (see Phenology below).

Status and Conservation

The Spesbona is rare and very localised. It is currently listed as Endangered in the IUCN Red List of Threatened Species. It was previously assessed as data deficient in 1996 and vulnerable in 2007 and 2010.

The species was first described in 1886 and, for a time, was thought to be possibly extinct until its rediscovery in 2003. The Spesbona is no longer present at the type locality in Ceres, probably due to over-extraction of water for the fruit industry. Spesbona angusta is threatened by the construction of dams, invasive plants such as Acacia mearnsii, and several invasive fish species.

Distribution

Spesbona angusta is endemic to the Western Cape, South Africa. Originally, the species was only known from near Ceres south to Franschhoek. However, additional populations have now been found to occur near Riversdale and in the Overberg between Bredasdorp and Elim, and in the Sedgefield/Knysna area. The Spesbona is likely to be more widespread than current records show.

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

Below is a map showing the distribution of records for Ceres Streamjack in the OdonataMAP database as of December 2024.

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

Further Resources

The use of photographs by Desire Darling and Gregg Darling is acknowledged. All other photographs by Ryan Tippett.

Spesbona Spesbona angusta (Selys, 1863). This species was moved from the genus Metacnemis in 2013.

Other common names: Ceres Streamjack, Ceres featherlegs, Ceres stream-damsel (Alt. English); Spesbona (Afrikaans)

Recommended citation format: Loftie-Eaton M; Navarro R; Tippett RM; Underhill L. 2025. Spesbona Spesbona angusta. Biodiversity and Development Institute. Available online at https://thebdi.org/2020/04/21/ceres-streamjack-spesbona-angusta/

References: Tarboton, M; Tarboton, W. (2019). A Guide to the Dragonflies & Damselflies of South Africa. Struik Nature.

Samways, MJ. (2008). Dragonflies and Damselflies of South Africa. Pensoft

Samways, MJ. (2016). Manual of Freshwater Assessment for South Africa: Dragonfly Biotic Index. Suricata 2. South African National Biodiversity Institute, Pretoria

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