Stout Pintail (Acisoma inflatum)

The photo above (by Wayne Johnston) can be viewed in OdonataMAP here.

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

Family Libellulidae

Acisoma inflatum STOUT PINTAIL

Identification

Small size

Hindwing – 22mm.

Easily recognised as an Acisoma species by the swollen abdomen base that tapers off sharply from segment 6 down to the tip.

Most similar to the Slender Pintail (Acisoma variegatum). The two species bear a close resemblance to one another and co-occur at many sites.

The most conclusive way to separate the two is the colouration difference, on the S4 ventral corner, along the sides of the abdomen. In A. variegatum the ventral corner is mostly white, while it is edged with black in A. inflatum. Additionally the S5 lateral carina is partly white in A. variegatum and all-black in A. inflatum.

Acisoma variegatum shows segments 6 and 7 of equal length, while in Acisoma inflatum segment 6 is shorter than segment 7.

Additionally Acisoma inflatum tends to be slightly smaller and somewhat duller in colour, sometimes showing a yellowish-brown wash on the thorax.

Click here for more details on identification.

Acisoma inflatum – Male
Okavango Delta, Botswana
Photo by Ryan Tippett

Habitat

Inhabits marshes and floodplains with pools that support a rich growth of aquatic plants, particularly sedge, reeds and grasses. May also be found along slow moving sections of rivers.

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

Behaviour

Sits close to the water on floating or emergent plant stems. Hunts from a perch and quickly resettles again. The flight is fast and wasp-like.

Status and Conservation

Locally common. Listed as of Least Concern in the IUCN Red List of Threatened Species. Most common in natural habitats but will make use of suitable man-made sites like dams and ponds.

Distribution

Acisoma inflatum occurs widely across the savanna regions of Sub-Saharan Africa. Also occurs very locally along parts of the Mediterranean coastline of North Africa.

In South Africa it is found in the higher rainfall areas of the north and east.

Below is a map showing the distribution of records for Stout Pintail 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.