Key to subfamilies of Vietnamese ants [Formicidae] based on the worker caste 1 Pygidium (abdominal tergite VII) flattened or impressed, posterolaterally with a single pair of spines (Fig. 2) or a series of peg-like spines (Fig. 3) ..................................................................................... 2 - Pygidium convex, unarmed (Fig. 4), but hypopygium (abdominal sternite VII) rarely armed with a series of spines posteriorly .................................................................................................... 3 2 Pygidium posterolaterally with a single pair of spines (Fig. 2); promesonotal suture distinct dorsally (Fig. 5) .................................................................................................. Dorylinae (Dorylus) - Pygidium posterolaterally with a series of peg-like spines (Fig. 3); promesonotal suture absent dorsally (Fig. 6) ..................................................................................................... Cerapachyinae 3 A single reduced and isolated segment, i.e. petiole (= abdominal segment II), present between mesosoma and gaster (Figs. 7, 8) .................................................................................................... 4 - Two reduced and isolated segments, i.e. petiole and postpetiole (= abdominal segments II and III), present between mesosoma and gaster (Fig. 9) .................................................................................... 11 4 Gastral segment II (= abdominal segment IV) arched and down-curved (Fig. 10) ................................... 5 - Gastral segment II neither arched nor down-curved (Figs. 11, 12) ................................................ 6 5 In full-face view antennal sockets mostly to entirely exposed, located a little in front of the line across mandibular bases (Fig. 13) or on a shelf-like frontoclypeal region overhanging mandibles (Fig. 14) ........................ Proceratiinae (part) - In full-face view antennal sockets mostly to entirely covered by frontal lobe, located a little behind the line across mandibular bases (Fig. 15) ............................................................... Ectatomminae (Gnamptogenys) 6 Petiole broadly attached to gastral segment I (= abdominal segment III); gastral segment I above helcium without a free anterior face (Fig. 16) .................................................................... Amblyoponinae (part) - Petiole narrowly attached to gastral segment I; gastral segment I above helcium with a free anterior face (Fig. 17) ......... 7 7 Antennal sockets located on shelf-like frontoclypeal region that overhangs the mandibles; frontal lobes fused to each other and forming a vertical plate (Fig. 18) ................................................. Proceratiinae (Probolomyrmex) - Antennal sockets located behind clypeus; shelf-like frontoclypeal region absent; frontal lobes variable in size and shape, but never forming a vertical plate (Fig. 19) ..................................................................... 8 8 Petiole extremely large and long; pygidium longer than gastral segment I (Fig. 20) ........... Amblyoponinae (Opamyrma) - Petiole relatively small and short; pygidium shorter than gastral segment I (Fig. 21) ................................. 9 9 Sting present and functional (even if the sting fully retracted, it may be seen through sternites of the abdominal apex); gastral tergite I (= abdominal tergite III) fused with gastral sternite I, but the suture present (Fig. 22) ................... Ponerinae - Sting absent; gastral tergite I largely or entirely separated from gastral sternite I (Fig. 23) ............................ 10 10 Apex of hypopygium forming acidopore which appears usually as a short nozzle surrounded by hairs (Fig. 24), or at least as a semicircular to circular emargination of the apical margin of the hypopygium (Fig. 25) ...................... Formicinae - Apical margin of hypopygium truncated, never forming acidopore (Fig. 26); hypopygium sometimes folded along its midline, and so apical margin of hypopygium showing a U- or V-shaped appearance but never forming a semicircular to circular emargination.................................................................................. Dolichoderinae 11 Pronotum and mesonotum completely separated by promesonotal suture (Fig. 27) ................................. 12 - Pronotum and mesonotum completely fused; promesonotal suture either entirely absent across dorsum of mesosoma (Fig. 28) or present as a weak transverse furrow .................................................................... 13 12 Eye well-developed (Fig. 29).. ................................................. Pseudomyrmecinae (Tetraponera) - Eye absent (Fig. 30) or, in intercastes of some Protanilla species, eye often present but consisting of only one or a few ommatidia...................................................................................... Leptanillinae 13 Postpetiole (= abdominal segment III) relatively massive, not much reduced in comparison with gastral segment I (= abdominal segment IV) (Fig. 31) .................................................... Proceratiinae (part of Proceratium) - Postpetiole much smaller than gastral segment I (Fig. 32) ..................................................... 14 14 When mouthparts fully closed, prementum (prm in Fig. 33) largely visible between stipites of maxillae (stp); antennal socket in full-face view usually (but not always) concealed, partly or entirely, by frontal lobe; antennal socket usually far from anterior margin of head; eye usually (but not always) present (Fig. 34).. ........................................ Myrmicinae - When mouthparts fully closed, prementum (prm in Fig. 35) not visible, or largely concealed behind labrum (lbr) and stipites of maxillae (stp) that meet along the midline (Fig. 35); antennal socket in full-face view fully exposed; clypeus narrow from front to back especially in front of antennal insertion, bringing the antennal sockets very close to the anterior margin of the head; eye always absent (Fig. 36) ................................................................ Aenictinae (Aenictus)

Published as part of Eguchi, K., Viet, B. T. & Yamane, S., 2011, Generic synopsis of the Formicidae of Vietnam (Insecta: Hymenoptera), Part I - Myrmicinae and Pseudomyrmicinae., pp. 1-61 in Zootaxa 2878 on page 7