BBFs! Butterflies, beetles & fossils: a unique heritage on our farm!
The elusive Elandsbergia butterfly
This small and beautiful butterfly was discovered on the summit of the Elandsberg mountains by E.L. and A.B. Pringle on 29th December 1982. There on the southern edge of the Karoo, the males fly on rocky ridges in arid Mountain Renosterbosveld, (referred to in Acocks (1975) as veld type 43, with some Macchia (Fynbos) elements).
A male will patrol its chosen, elevated rocky prominence, waiting for a female to ascend and mate. The males defend their territory vigorously against other males. After mating, the female will descend and search the slopes for suitable foodplants on which to lay her eggs. She will only do so if a certain species of ant is present on the foodplant. The butterflies in this genus are commonly referred to as "Opals", this is because of the opal-like colour on the wings, but also for the deeper blue iridescence on the wings of males when light is reflected at certain angles. Females have rather more orange markings, have more rounded wings and they lack the iridescence. This genus of butterflies are known for associating with certain ants during their larval stages. The ants are usually a species of "cocktail ant" (Crematogaster sp.). These ants tend the caterpillars and protect them from predators in exchange for a special nectar exuded from a dorsal gland by the caterpillar. During the early evening, the caterpillars emerge from their hiding places beneath the foodplant to feed on the foliage whilst some of the ants rush about looking for any enemy predators. The most likely foodplants for this butterfly are Zygophyllum and Thesium, both of which are present in suitable places on the mountain and were also growing close to where females were seen. On this trip it was noted that Crematogaster ants were present on both likely foodplants. This butterfly is on the wing during the months of October to December. Although its existence has been known for 25 years, it was only scientifically described and named by Heath & Pringle in 2007. It was described conservatively as a subspecies of Chrysoritis adonis adonis from the Gydo Mountain near Ceres, however, its behaviour and other small differences suggest it may be a distinct species in its own right. The ongoing molecular work at Harvard University (USA) may throw more light on its true status, as researchers compare its DNA with other closely related species. |
Elandsbergia is a butterfly species discovered in the late 1800s which is found only on our farm - entymologists come from many different countries to study this rare butterfly.
The Elandsberg Opal (Chrysoritis adonis aridimontis) Heath & Pringle, 2007 |
Meet Zandrivier's flower beetleIn 2014 Prof. Renzo Perissinotto (PhD, Pr Sci Nat) from the Department of Zoology at Nelson Mandela Metropolitan University, visited Zandrivier and discovered a new flower beetle species. Meet Trichostetha curlei, unique to our farm. |
Zandrivier's many fossils and interesting geology
With its fossils, well-exposed rocks and proximity to Seweweekspoort, Zandrivier Farm is geologically very interesting. It is one of the highest farms in the Western Cape and is 115 km from the sea, so how did marine shell fossils end up in its rocks. To answer that, we have to go back 510 million years when deposition of sediments of the Cape Supergroup began. At the time the area which is now Zandrivier lay in a shallow southern ocean called the Agulhas Sea, the coast of southern Africa lying to the north. For about 170 million years, tons of mud and sand were deposited, transported from the southern African hinterland by large river systems to the sea. Life existed in this ocean in the form of invertebrates (soft bodied animals, some with shells) living on the sea-floor. Along with the sedimentation these sea animals were buried and preserved, and the sediments were compacted under their own weight, eventually forming rock.
The Zandrivier shell fossils are called brachiopods (lamp shells – see photo below) which were filter feeders attached to the sea floor. The largest shell in the photo below, which looks like a swallow with spread wings, belongs to the order Spiriferida which is now extinct.
Other fossils found at Zandrivier include crinoids, also called feather stars or sea lilies due to their long stem and flower-like arms but they are in fact animals. They are related to sea-urchins and starfish and are also filter feeders. In the photo below left, the jointed sections are crinoid stems made from disc-shaped pieces of endoskeleton while the round indents are fossil discs from the stems.
The Zandrivier shell fossils are called brachiopods (lamp shells – see photo below) which were filter feeders attached to the sea floor. The largest shell in the photo below, which looks like a swallow with spread wings, belongs to the order Spiriferida which is now extinct.
Other fossils found at Zandrivier include crinoids, also called feather stars or sea lilies due to their long stem and flower-like arms but they are in fact animals. They are related to sea-urchins and starfish and are also filter feeders. In the photo below left, the jointed sections are crinoid stems made from disc-shaped pieces of endoskeleton while the round indents are fossil discs from the stems.
The deformed and folded rocks that you can see whilst driving through Seweweekspoort are some of the best examples of intensely folded rocks of the Belt. The main compressional force came from the south resulting in the roughly east-west trend of the mountain chain. This can be seen in the image below which shows a section of the Cape Fold Belt with the Zandrivier homestead in the centre. To the south one can see the hard, light coloured sandstone and quartzites of the Table Mountain Group with Seweweekspoort cutting through it. These erosion-resistant rocks form the most dramatic folding and therefore some of the highest mountains, like the Swartberg, in the Belt. To the north lies a band of darker, softer Bokkeveld shales and siltstones. Erosion of these rocks has created flatter areas as well as fertile soils suitable for cultivation and thus many farms of the Klein Karoo occur on Bokkeveld rocks. Because they are finer grained and less deformed, they contain most of the fossils found in the Cape as well as those on Zandrivier. To the north (in the left hand corner of the photo) further light-coloured quartz sandstones of the Witteberg group can be seen. These are also hard, erosion resistant rocks and form the mountains that you see to the North from the Zandrivier cottages.
Sources
Compton, J. S. 2004. The Rocks and Mountains of Cape Town. Double Story Books.
McCarthy, T and Rubidge, B. 2005. The Story of Earth and Life. A southern African perspective on a 4.6-billion- year journey. Struik Nature.
Norman, N and Whitfield, G. 2006. Geological Journeys. A traveller’s guide to South Africa’s rocks and landforms. Struik Publishers.
"Haeckel Crinoidea"; by Ernst Haeckel - Kunstformen der Natur (1904), plate 20: Crinoidea . Licensed under Public Domain via Commons -
https://commons.wikimedia.org/wiki/File:Haeckel_Crinoidea.jpg#/media/File:Haeckel_Crinoidea.jpg
Download this article as a PDF here
Compton, J. S. 2004. The Rocks and Mountains of Cape Town. Double Story Books.
McCarthy, T and Rubidge, B. 2005. The Story of Earth and Life. A southern African perspective on a 4.6-billion- year journey. Struik Nature.
Norman, N and Whitfield, G. 2006. Geological Journeys. A traveller’s guide to South Africa’s rocks and landforms. Struik Publishers.
"Haeckel Crinoidea"; by Ernst Haeckel - Kunstformen der Natur (1904), plate 20: Crinoidea . Licensed under Public Domain via Commons -
https://commons.wikimedia.org/wiki/File:Haeckel_Crinoidea.jpg#/media/File:Haeckel_Crinoidea.jpg
Download this article as a PDF here
Christo V het ons in September 2020 besoek:
"Die eienaar Ben en personeel veral Sannah het uit hulle pad gegaan om ons verblyf so aangenaam as moontlik te maak.
Die ligging is ideaal on die omgewing te leer ken die uitsig op die Swart Berge is asemrowed. Was lekker om weer so verskeidenheid plaasdiere te sien en die vriendelike hondekinders!"