The Black-eyed Susan (Thunbergia alata) is a vine that occurs naturally from tropical East Africa to eastern South Africa. It grows on forest margins and is attractive to both bees and butterflies. I have a self-sown one growing next to our swimming pool.
These flowers have also featured on South African postage stamps, which are illustrated below:
I have only now noticed – 17 years later – that the Black-eyed Susan is referred to on the stamps as Black eyed Susy (a name I am not familiar with)! These stamps were first issued in 2000 and reissued in 2003 as part of the standard postage series, which continued for a long time afterwards. In the image you can see them featured alongside a giant girdle-tailed lizard (a 5c stamp issued in 2000) and a much older stamp in a series that featured wild animals of South Africa, this one being a blue wildebeest, issued in 1998.