[1] Myrmecia pyriformis was first described by British entomologist Frederick Smith in his 1858 publication Catalogue of hymenopterous insects in the collection of the British Museum part VI, based on a syntype worker, queen and male collected from Melbourne and the Hunter River.

Smith notes that M. pyriformis is very similar in appearance to M. forficata, though he comments all sexes are larger, the male is strikingly distinct and the head is more square shaped and not narrowed from the back end.

Smith also described M. sanguinea from Tasmania in the same publication he described M. pyriformis, now treated as a junior synonym.

[9] Due to its similar appearance to M. forficata, Auguste Forel believed M. pyriformis was a subspecies, rather than a full species.

M. pyriformis is typically larger, the colour is darker and the head and alitrunk (a segment of the body where the wings are attached) are either dark reddish-brown or blackish-brown.