1. The body size differs significantly between the castes in seven parts measured: Head width, width of mesonotum, alitrunk length, widths and lengths of first and second gastral tergites.

2. Features of P. annosus unique for the large recent genus Polyrhachis include a large first gastral segment, a scapus attached at some distance from the clypeus, and an alitrunk (mesosoma) and petiole each with a pair of teeth or spines.