Last night my brother was stung by something that looked a lot like the Myrmecia piliventris. I didn't take a picture (I was too busy trying to kill it), but I found Alex Wild's photo on the internet, and the thing that bit my brother looked a lot like it.
I read on Wikipedia that these ants are mostly found in Australia, and since we live in Namibia, I was wondering what it could be? Any idea?
Next time, kill the ant more carefully! (or better yet, photograph it alive, like Alex Wild would). Without specific information about which parts of the ant reminded you of Myrmecia, it's hard to say what species it was. One thing I'm fairly certain of is that it is not Myrmecia piliventris. Unless you or one of your neighbors just came back from a trip to Australia, it's pretty unlikely that genus would show up anywhere outside of Australia, or the islands immediately next to it (Myrmecia is also native to New Caledonia). Members that genus have been reported by New Zealand quarantine officers, though, so it's not impossible that commerce will one day introduce a "bulldog" ant to some place beyond the land down under.
I'd say your best bet is to check our Ants of Kenya page. It's still not exactly Namibia, but the genera at least are much more likely to occur in both Kenya and Namibia than Australia and Namibia.
If it was the mouthparts (mandibles) of Myrmecia that reminded you of the ant that stung your brother, then some possibilities that leap to mind are the genera Leptogenys and Plectroctena. Plectroctena can grow quite large (with a headwidth of 4mm). Leptogenys are generally smaller, and look as if they are probably faster. Although they do have pretty noticeable stings, it would have been difficult to see the mandibles on most Leptogenys species I'm aware of without using a microscope, so I doubt it's that one.
Another noteworthy trait that Myrmecia has are their large eyes. In Africa, Asia, and Australia, the ants with some of the largest eyes relative to their head sizes belong to the genus Tetraponera. These ants (and their relatives in the Americas, Pseudomyrmex) have some of the largest eyes in the ant family, and their elongate bodies are similar in shape to the bodies of Myrmecia. While some Tetraponera can grow quite large and be rather aggressive, like the Southeast Asian Tetraponera rufonigra, I can't find evidence that there is a Tetraponera that big in West Africa.
In many parts of the world, especially in the tropics, if a medium-large ant has just painfully stung you, there's a good chance it belongs to the genera Pachycondyla or Odontomachus. These don't bear a specific resemblance to Myrmecia (Odontomachus does have elongate mandibles, but they are attached near the midline of their faces, rather than at the corners as in Myrmecia, Plectroctena, and Leptogenys), but they might be more common in some places than other genera mentioned in this post.
Good luck! Feel free to send us pictures if you see an ant like that again!
Jesse Czekanski-Moir & the AntAsk Team