My take on Tabanidae ID:
Tabanidae can be recocnized by the third antennal segment which is elongate and has a cylindrical extension with rings (or annulations) that appear like miniature segments and the absence of large setae on body and legs. A less formal but painful means of identification is that most relatively large flies that bite are female tabanids.
The largest species in South Africa are
Tabanus biguttatus, T. ustus, Philoliche rostrata and
P. aethiopica with a length of about 23 mm.
A study in the south-eastern KNP sampled these species:
Tabanus minuscularius, Tabanus chevalieri, Tabanus gratus, Tabanus atrimanus, Tabanus cf. sericiventris, Atylotus agrestis, Chrysops obliquefasciata, Philoliche (Buplex) suavis, Haematopota vittata, Haematopota decora and
Haemotopota daveyi. The dominant species from the sampled sites was
Tabanus minuscularius.
Tabanus atrimanus also has a white coloured pattern of median triangular spots on the abdomen.
https://repository.up.ac.za/bitstream/h ... sequence=1
I don't know how much of variation there is within a species, but none of the
Tabanus sp with triangular spots I have seen on photos matches the one we have. None of the descriptions mentions eye patterns similar to the one we have.
I guess there are numerous other species in the area that look similar and we have one of these.