Hi Senex, Myrmecia nigriceps and M. forficata are pretty similar. M. nigriceps is probably more common, but I'm pretty sure your ant is M. forficata, and is only the third record on CNM of this species. The shape of the mandibles and their reddish colour sets it apart from M. nigriceps which almost always has yellowish mandibles. There are quite a few reasonable photos of life M. forficata on the Atlas of Living Australia website. Cheers, Jon