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The Knysna Skolly, Thestor brachycerus brachycerus was discovered and described at Knysna in 1883 by Roland Trimen (discoverer of the Brenton Blue) and is now red-listed as 'critically endangered'.

Its rarity is due to its very narrow habitat specificity, small geographic range (it is still only known from Knysna) and its low abundance. There has been a declining population trend since the 1960s and this has accelerated since 1980 due to habitat loss from mainly property and golf estate developments but also from changes in farming practices on the Woodbourne Farm, where the butterfly used to flourish. 

The Knysna Skolly derives its name from its scruffy appearance. The upper side of the butterfly is a pale greyish-brown with prominent darker markings on the fore and hind wings. The wing margins are chequered black and white. 

The underside of the wings are a mosaic of grey and black markings. The Knysna Skolly has only ever been recorded on the Eastern Heads of Knysna. It has been found on fynbos-covered North, North-West and North-East facing slopes at an altitude of 10m to 180m above sea level, but also remarkably at an altitude of less than 10m adjacent to the sea shore on a South facing, predominately grassy flat area. There are currently only two known extant populations; one colony at Pezula Golf Estate below the sixth fairway of the golf course, and another close to the sea at Coney Glen. 

The butterfly can cope with an intermediate level of disturbance such as low intensity cattle grazing. At higher disturbance intensities, such as where there is regular burning or where sheep grazing is practiced, it cannot persist. When the vegetation gets too dense and overgrown the butterfly disappears, since it prefers many small open patches within the habitat. The opening up of hand-cut paths at the colony site at Pezula has been completed by the Pezula Golf Estate management team to encourage occupation by the butterfly. Unlike the majority of butterflies, the adults do not feed on nectar from flowers and their larvae do not appear to feed on plants. They are believed to have an association with ants and Homopterans (aphid-like insects) from which they obtain an as yet undiscovered food source. 

The Knysna Skolly is predated on by birds; specifically, predation by Karoo Prinia has been observed. Camouflage is the butterfly's primary method of defence. 

Territorial males engage in aerial interactions with other male butterflies which involve the male leaving its perching site and circling around the intruder. These non-contact interactions usually result in one butterfly returning to the perching site after chasing the other one off. 

The majority of eggs are deposited on the underside of plant leaves. It is known that the eggs hatch in 12 or 13 days after being laid but what happens to the larvae after that is unknown. Ecological investigations through sampling of vegetation and of insect communities have revealed dramatic differences between the two known remaining sites. These insights have enabled implementation of a habitat management plan including the creation of new habitat on adjacent land with the aim of increasing its population to sustainable levels to avoid extinction. The Pezula Golf Estate management team are currently assisting researchers by helping to preserve and extend the colony at Pezula. 

Source: Knysna-Plett Herald (Written by Dave Edge.)
Jul 17, 2016