Ants of Vietnam

The ants of Vietnam has been a ongoing focus of three researchers: Katsuyuki Eguchi, Tuan Viet Bui and Seiki Yamane.

There is a website of Vietnamese ants by Eghuci and Bui.

This antwiki page currently serves to gather in one place some of the information, and links to related pages, about Vietnamese ants. You can see a list of species here: Vietnam.

Amblyoponinae
Key to Vietnamese Amblyoponinae Genera

Myopopone
Morphology. Workers of Vietnamese species have the following features:

Worker monomorphic, but sometimes varying greatly in size; head in full-face view subrectangular, without distinct genal angle beside each mandibular insertion; preoccipital lobe absent dorsally and laterally; frontal carina vestigial or absent; antennal scrobe absent; frontal lobes large, relatively narrowly separated from each other by posteromedian portion of clypeus, expanded anteriad beyond anterior margin of clypeus; antennal sockets in full-face view completely concealed by frontal lobe, located relatively close to anterior margin of head; anteromedian margin of clypeus straight or weakly concave, often with a series of tiny stub-like processes, defined laterally by distinct angles; mandible elongate, narrowly blade-like, with ca. 10 teeth that are indistinctly arranged as two rows; antenna 12-segmented; apical few segments of antenna distinctly flattened in cross-section; eye reduced, consisting of a few ommatidia, situated behind midlength of side of head; mesosoma in lateral view somewhat of box-form; mesonotum present as a conspicuous transverse disc margined anterially by flexible promesonotal suture and posteriorly by distinct metanotal groove; propodeum unarmed; propodeal lobe vestigial; outer surface of middle tibia and basitarsus with thickened peg-like setae mixed with the normal finer pilosity; petiole forming indistinct anterior peduncle, broadly attached to gaster, in lateral view without a free posterior face; subpetiolar process present; abdominal segment III with a free anterior face below helcium only; girdling constriction between abdominal segments III and IV weak; pygidium large, convex across; pygidium and hypopygium unarmed laterally and posteriorly; sting well developed.

Differentiation. The worker of Myopopone is similar to that of Stigmatomma, but in the latter all of the antennal segments terete, not flattened.

The only species of this genus occurring in Vietnam is Myopopone castanea. It occurs in well-developed forests, and nests in large rotting logs. Nest chambers are usually excavated deep inside logs.

Mystrium
Morphology. The worker of the sole Vietnamese species, Mystrium camillae has the following features:

Worker monomorphic; body bearing spatulate hairs; head in full-face view rectangular, with broadly and deeply concave posterior margin, with a short and stout genal spine beside each mandibular insertion; preoccipital carina absent dorsally and laterally; frontal carina and antennal scrobe absent; frontal lobes relatively widely separated by posteromedian portion of clypeus, in full-face view completely concealing antennal sockets, not reaching anterior margin of clypeus; anteromedian portion of clypeus roundly convex anteriad; anterior clypeal margin with a series of 6–8 processes on which a stub-like, very short seta present; mandible elongate, narrowly blade-like, with widened round apex; masticatory margin serrate, with two rows (dorsal and ventral rows) of teeth; antenna 12-segmented, with inconspicuous 4-segmented club; apical segments of antenna never flattened in cross-section; eye absent or present as a single ommatidium; if eye present, it located around midlength of side of head (excluding genal spine); mesosoma in lateral view short and high; promesonotal suture present and flexible; metanotal groove indistinct dorsally; propodeum unarmed; propodeal lobe very low; petiole without distinct anterior peduncle, broadly attached to gaster, in lateral view without a free posterior face; subpetiolar process present; abdominal segment III with a free anterior face below helcium only; girdling constriction between abdominal segment III and IV indistinct; pygidium large, convex across, unarmed laterally and posteriorly; hypopygium armed with a few short spinose setae posteriorly; sting well developed.

Differentiation. The worker of Mystrium is somewhat similar to that of Stigmatomma, but in the latter the apex of mandible is pointed, and the body is covered with simple hairs.

Prionopelta
Morphology. Workers of Vietnamese species have the following features: Worker monomorphic; head in full-face view subrectangular; preoccipital carina absent dorsally and laterally; frontal lobes small, horizontal, separated from each other by a longitudinal sulcus; antennal sockets in full-face view largely concealed by frontal lobe, located relatively far from anterior margin of head; anteromedian portion of clypeus relatively long anteroposteriorly, roundly convex anteriad; anterior clypeal margin with a series of ca. 15 processes on which a stub-like, very short seta present; mandible elongate-triangular; masticatory margin with 3 teeth; antenna 12-segmented; apical 4 segments forming a club; eye reduced, consisting of a few ommatidia, a little behind midlength of side of head; mesosoma in lateral view almost flat dorsally; promesonotal suture present and flexible; metanotal groove usually distinct dorsally; propodeum unarmed; propodeal lobe very low; petiole without anterior peduncle, broadly attached to abdominal segment III, in lateral view without a free posterior face; petiolar process well developed, anteriorly with a conspicuous round depression; abdominal segment III with a free anterior face below helcium only; girdling constriction between abdominal segment III and IV weak; pygidium large, convex across; pygidium and hypopygium unarmed laterally and posteriorly; sting well developed.

Differentiation. The worker of Opamyrma is easily distinguished from that of the other Vietnamese genera of Amblyoponinae by its elongate-triangular mandible.

The only record of this genus is of two individuals of Prionopelta sp. collected in sandy soil of Sang Le Forest, Pu Mat National Park.

Stigmatomma
Morphology. Workers of the Vietnamese species have the following features (see also Schmidt & Shattuck 2014):

Worker monomorphic; head in full-face view usually subrectangular, with genal angle beside each mandibular insertion which is rarely developed well as a small, triangular spine; preoccipital carina weak or absent dorsally and laterally; frontal lobes present, narrowly separated by posteromedian portion of clypeus, or approximate to each other; frontal carina rarely present; antennal scrobe absent; antennal sockets in full-face view at least partly concealed by frontal lobe; anterior margin of clypeus usually with a series of dents (see below); mandible elongate, narrowly blade-like with pointed apex, without basal margin; masticatory margin with one or two rows (dorsal and ventral rows) of teeth; antenna 11- or 12-segmented; eye relatively reduced or absent; eye, if present, situated behind midlength of side of head; mesosoma in lateral view with a flat or weakly arched dorsal outline; promesonotal suture present and flexible; metanotal groove absent dorsally; propodeum unarmed; propodeal lobe low or almost absent; petiole essentially sessile, but rarely with a distinct short anterior peduncle; broadly attached to abdominal segment III, in lateral view without a free posterior face; subpetiolar process present; abdominal segment III with a free anterior face below helcium only; girdling constriction between abdominal segment III and IV moderate to weak; pygidium large, convex across, laterally and posteriorly unarmed; hypopygium often armed with a series of spines posteriorly; sting well developed.

Differentiation. The worker of Stigmatomma is somewhat similar to that of Myopopone, but in the latter a few apical segments of the antenna are distinctly flattened.

A single worker specimen of Stigmatomma sp. eg-4 (collected from a dry dwarf forest of southern central Vietnam) is morphologically very distinct from the other Vietnamese species. It lacks a series of dents on the anterior clypeal margin; instead it has a plate-like projection just dorsal to the junction between the clypeus and labrum. This feature seems to be equivalent to a diagnostic characteristic of the worker of Xymmer discussed by Yoshimura and Fisher (2012) which recorded a male of Xymmer from Thailand. In order to confirm the identity of Stigmatomma sp. eg-4, colony samples containing males may be needed.

Dorylinae
Key to Vietnamese Dorylinae Genera

Aenictus
Morphology. Workers of Vietnamese species have the following features (see also Terayama & Kubota 1993; Bolton 1994; Jaitrong & Yamane 2011; Jaitrong & Hashimoto 2012; Jaitrong et al 2012; Jaitrong & Yamane 2013):

Worker monomorphic, but sometimes varying widely in size; head in full-face view usually round or subrectangular; preoccipital carina usually present dorsally and laterally; frontal lobe present as narrow vertical carinae, very narrowly separated from each other by a longitudinal strip of posteromedian portion of clypeus, and sometimes fused together posteriorly; antennal socket in full-face view fully exposed, very close to the anterior margin of head; parafrontal carina often present; clypeus narrow from front to back especially in front of antennal insertion; mandible linear to triangular; when mouthparts fully closed, prementum not visible, or largely concealed behind labrum and stipites of maxillae that meet along the midline (see fig. 35 of Eguchi 2011); antenna 10- segmented; eye absent; mesosoma in lateral view box-shaped, or with sinuate dorsal outline; promesonotal suture absent; metanotal groove usually indistinct or absent but rarely distinct dorsally; metapleural gland orifice concealed beneath a ventrally directed cuticular flap or flange; propodeum unarmed, but posterior face often margined dorsally and laterally with distinct ridges; propodeal lobe usually (but not always) low or indistinct; apicoventral part of metatibia with a longitudinally elongate gland opening; waist consisting of two small segments (petiole and postpetiole); petiole sessile to subsessile; spiracles on abdominal segments V–VII shifted backwards, usually not concealed by posterior margins of preceding segments; pygidium reduced to a narrow U-shaped sclerite, laterally and posteriorly unarmed (lacking teeth or peg-like spines); sting developed.

Differentiation. The worker of smaller species of Aenictus is somewhat similar to that of Leptanilla, but in the latter the promesonotal suture is present and flexible, and the spiracles on abdominal segments V–VII are concealed by the posterior margins of the preceding segments.

The Aenictus ceylonicus group is in need of revision. The species determined as Aenictus dentatus by Zryanin may be Aenictus paradentatus. At present, Aenictus dentatus is assumed to not be present in Vietnam.

Cerapachys
Morphology. Workers of Vietnamese species have the following features.

Worker monomorphic, but sometimes varying widely in size; head in full-face view usually subrectangular; posterolateral portion of head usually (but not always) expanded posteroventrad as a lobe or forming a flange; preoccipital carina usually distinct dorsally and laterally; frontal lobes vertically raised, very narrowly separated from each other by a longitudinal strip of median portion of clypeus, and often fused together posteriorly; antennal socket in full-face view fully exposed; antennal scrobe absent, but in most species area around antennal socket somewhat impressed or flattened, margined laterally by parafrontal carina (in the Cerapachys sexspinus group parafrontal carina completely absent); clypeus narrow from front to back especially in front of the antennal insertion, sometimes forming an anterolateral projection just above each mandibular insertion; mandible subtriangular, edentate or armed with minute teeth on masticatory margin; antenna 9- to 12-segmented; scape clavate, short, not exceeding beyond posterior corner of head; apical segment usually bolbous; eye varying from vestigial to well developed, or sometimes absent; mesosoma in lateral view relatively robust and box-shaped, often strongly marginate anterodorsally; promesonotal suture absent or vestigial dorsally; metanotal groove absent; metapleural gland orifice concealed beneath ventrally directed cuticular flap or flange; propodeum unarmed; posterior face margined with distinct ridge dorsally and/or laterally; propodeal lobe usually developed well; mesotibia and metatibia with a pectinate spurs; pretarsal claw of all legs sometimes with a preapical tooth; petiole sessile to subsessile, with subpetiolar process; abdominal segment III with a graded reduction from a full-sized segment (as in the C. sexspinus group) to a small postpetiole; abdominal segments IV, V and VI without girdling constriction separating them; abdominal spiracles V–VII shifted backwards, usually not concealed by posterior margins of preceding segments; pygidium large; the dorsum flattened or impressed, with lateral and posterior margins armed with a series of small teeth or peg-like spines; sting large and strongly developed.

Differentiation. The worker of Cerapachys is similar to that of Simopone, but in the latter the frontal lobes are relatively broadly separated from each other by the median portion of clypeus, the antennal socket in full-face view is partly concealed by the frontal lobe, and tibial spurs are absent from middle legs (at most a setiform vestige may remain).

Bionomics. Cerapachys species nest in rotting logs and wood fragments, under stones, and in leaf litter and soil. Some species seem to be semi-nomadic, and their colony size is much larger than cryptic congeners of which colony size may not exceed a hundred.

Dorylus
Morphology. Workers of Vietnamese species have the following features (see also Bolton 1994, Eguchi et al. 2014):

Worker polymorphic; head in full-face view usually subrectangular (but rarely heart-shaped in minor worker); preoccipital carina absent; frontal lobes present as narrow vertical carinae, narrowly separated from each other by a longitudinal strip of median portion of clypeus, and in minor worker often fused together posteriorly; antennal socket in full-face view fully exposed, very close to anterior margin of head; clypeus usually narrow from front to back especially in front of antennal insertion (but in minor worker median portion of clypeus occasionally produced anteriad as a round or triangular lobe); mandible usually (but not always) falcate; antenna 8 to 12- segmented; eye absent; mesosoma in lateral view box-shaped; promesonotal suture conspicuous but pronotum and mesonotum fused, immobile with respect to each other; metanotal groove absent; metapleural gland orifice concealed beneath a ventrally directed cuticular flap or flange; propodeum unarmed; orifice of propodeal spiracle subtended by an endophragmal pit and a longitudinal impression (the impression often inconspicuous); propodeal lobe absent; metatibial gland present; waist consisting of a single small segment (petiole); petiole without tergosternal fusion; subpetiolar process usually (but not always) developed as a lobe; abdominal segment III with tergosternal fusion; spiracles on abdominal segments V–VII shifted backwards, not concealed by posterior margins of preceding segments; pygidium large; its dorsum flattened or impressed, posteriorly with a pair (or rarely two pairs) of spines; sting reduced.

Differentiation. The worker of Dorylus is superficially similar to that of the Cerapachys sexspinus group, but in the latter the promesonotal suture is completely absent, and the pygidium is armed with a series of peg-like spines posteriorly.

Simopone
Morphology. Although no Vietnamese specimens of this genus were examined in the present study, according to Radchenko (1993b) and Bolton & Fisher (2012), workers of a known Vietnamese species of this genus (Simopone oculata) may show the following features:

Head in full-face view elongate, with sides almost parallel, without a differentiated vertical posterior surface above occipital foramen (instead vertex slopes evently down to upper margin of occipital foramen); preoccipital carina distinct; frontal lobe not vertically raised, in full-face view concealing at least inner margins of antennal sockets; the lobes relatively widely separated from each other by posteromedian portion of clypeus; frontal carina reaching dorsal margin of eye; parafrontal ridge almost reaching anterior margin of eye; mandible subtriangular, armed with minute teeth on masticatory margin; antenna 11-segmented; scape clavate, short; segment II to apical segment short and gradually incrassate; eye large; ocelli present but minute; mesosoma elongate with its dorsolateral borders right-angled; pronotum marginate anteriorly; promesonotal suture represented by transverse trace dorsally but distinct laterally; metanotal groove poorly visible dorsally but distinct laterally; mesotibia without spurs (at most a setiform vestige may remain that cannot be distinguished by light microscopy from other setae at tibial apex); metatibia with a single pectinate spur; metabasitarsus ventrally with a longitudinal glandular groove that occupies at least basal half of tarsomere length; pretarsal claws of all legs with a single preapical tooth on inner margin; propodeum unarmed, but posterior face margined dorsally and laterally with a distinct ridge; petiole in lateral view elongate and compressed dorsoventrally, with a transverse anterior carina.

Differentiation. The worker of Simopone is similar to that of Cerapachys, but in the latter the frontal lobes are very narrowly separated from each other by a longitudinal strip of the median portion of clypeus, the antennal socket is in full-face view almost completely exposed, and one or two tibial spurs are present on middle legs.

Bionomics. Radchenko (1993b) mentioned that the holotype (worker) of S. oculata was collected under a stump in a secondary tropical forest, but the life history of the species is unknown.

Leptanillinae
Key to Vietnamese Leptanillinae Genera

Leptanilla
Morphology. Workers of Vietnamese species have the following features:

Worker monomorphic; body slender; head in full-face view oval or subrectangular, and somewhat flattened dorsoventrally; preoccipital carina present dorsally and laterally; frontal lobe, frontal carina and antennal scrobe absent; antennal sockets in full-face view fully exposed, very close to the anterior margin of head, separated from each other by a median longitudinal ridge of clypeus; median portion of clypeus produced anteriad as a lobe; lateral portion of clypeus narrow from front to back in front of antennal insertion; mandible narrowly blade-like and curved; masticatory margin with 3 distinct teeth; inner face of basal shaft of mandible with a spatulate lobe; antenna 12-segmented; eye absent; mesosoma slender, in lateral view flattened dorsally; promesonotal suture present and flexible; metanotal groove vestigial or absent dorsally; propodeum unarmed; propodeal lobe absent; waist consisting of two small segments (petiole and postpetiole); petiole without anterior peduncle; its tergosternal fusion complete, without trace of a sutrue; petiolar and postpetiolar spiracles located on lateral face of anteriormost part of petiolar and postpetiolar nodes, respectively; postpetiolar sternite swollen strongly; spiracles on abdominal segments V–VII concealed by posterior margins of preceding segments; pygidium relatively large, convex across, laterally and posteriorly unarmed (lacking teeth or peg-like spines); sting well developed.

Differentiation. The worker of Leptanilla is somewhat similar to that of the smaller species of Aenictus and Cerapachys, but in the latter two genera the promesonotal suture is absent and the spiracles on abdominal segments V–VII are usually not concealed by the posterior margins of the preceding segments.

Opamyrma
Morphology. Worker presumably monomorphic; body long and slender, with long legs; head in full-face view subrectangular, and somewhat flattened dorsoventrally; preoccipital carina complete, almost encircling the head slightly before its posterior margin; frontal lobe, frontal carina and antennal scrobe absent; median part of clypeus rather clearly divided into posterior horizontal portion and anterior steep slope; the posterior portion distinctly separated from frons with a continuous carina, and broadly inserted between antennal sockets; lateral part of clypeus narrow from front to back; mandible slender, with long but bluntly tapered apical tooth followed by a trapezoidal lobe and three inconspicuous teeth; labrum on its outer face with at least two rows of peg-like denticles; eye absent; antennal sockets completely exposed in full-face view, located in a large, roundly excavated area whose anterior wall is steep just behind posterior margin of clypeus; antenna 12-segmented, gradually incrassate from segment II to XII; mesosoma slender, in lateral view flattened dorsally; promesonotal suture present and flexible; metanotal groove absent dorsally; propodeum unarmed; orifice of propodeal spiracle round, situated relatively low on lateral face of propodeum; propodeal lobe much reduced; mid- and hind tibiae each with a reduced barbulate anterior spur in front of a well-developed pectinate posterior spur; waist consisting of a single segment (petiole); petiole extremely elongate, virtually without anterior peduncle, narrowly attached to abdominal segment III; tergo-sternal sutures of petiole present; petiolar spiracle located anteriorly on lateral face of petiole at its mid-height; gaster (consisting of abdominal segments III–VII) extremely elongate; abdominal segment III above helcium with free anterior face; spiracles on segments V–VII concealed by the preceding segments; segment VII longest among the segments III–VII; pygidium and hypopygium unarmed laterally and posteriorly.

The worker of Opamyrma hungvuong, the only species of this genus in Vietnam, is distinguishable by a combination of the following features: petiole narrowly attached to abdominal segment III (gastral segment I); abdominal segment III above helcium with free anterior face; frontal lobe completely absent, thus antennal socket in full-face view fully exposed.

Protanilla
Morphology. Workers of Vietnamese species have the following features.

Worker monomorphic; head in full-face view somewhat elongate trapezoidal; preoccipital carina present but weak dorsally and laterally on head; frontal lobe, frontal carina and antennal scrobe absent; antennal sockets in full-face view fully exposed, very close to anterior margin of head, widely separated from each other by clypeal disc; clypeal disc trapezoidal, raised, and flattened or weakly concave medially, margined laterally with a sharp edge running from mandibular insertion to junction with frons; mandibles subtriangular; masticatory margin of mandible with small peg-like teeth; inner surface of mandible with peg-like teeth (modified setae) and thick setae; antenna 12-segmented; eye absent (but intercaste often with reduced eye consisting of a few ommatidia); mesosoma in lateral view with almost straight dorsal outline, or promesonotum feebly raised; promesonotal suture present and flexible; metanotal groove conspicuous dorsally; propodeum unarmed; orifice of propodeal spiracle round, situated relatively low on lateral face of propodeum; propodeal lobe absent; waist consisting of two small segments (petiole and postpetiole) which have clearly differentiated posterior faces; petiole without anterior peduncle; its tergosternal fusion complete, without trace of sutrue; its sternite swollen strongly and forming anteroventral flange; petiolar and postpetiolar spiracles located on the side of anteriormost part of the petiolar and postpetiolar nodes, respectively; postpetiole almost as long as or longer than broad, not distinctly broader than petiole, lacking tergosternal fusion; its sternite swollen strongly; abdominal spiracles V–VII concealed by the posterior margins of the preceding segments; pygidium large, convex across its width, laterally and posteriorly unarmed; sting well developed.

Differentiation. The worker of Protanilla is easily distinguished from that of the other genera known from Vietnam by a combination of features: antennal sockets in full-face view fully exposed; clypeal disc trapezoidal, raised and flattened, margined laterally with a sharp edge; inner surface of mandible with peg-like teeth; promesonotal suture present and flexible; waist consisting of two small segments (petiole and postpetiole) which have clearly diffintiated posterior faces.

Myrmicinae
Key to Vietnamese Myrmicinae Genera

Myrmica
Key to Myrmica of Vietnam

Pheidole
Key to Pheidole of North Vietnam

Ponerinae
Key to Vietnamese Ponerinae Genera

Anochetus
Morphology. Workers of Vietnamese species have the following features (see also Schmidt & Shattuck 2014):

Worker monomorphic; lateral outline of head in full-face view with a distinct convexity of which the anterodorsal face has eye; vertexal lobe well developed; vertex without a median longitudinal carina; preoccipital carina distinct dorsally and laterally; posterior face of head inside a conspicuous preoccipital carina without a pair of dark lines; frontal lobe horizontal, partly to largely concealing antennal socket; antennal scrobe absent; submedian portion of clypeus more or less expanded above each mandibular base; posteromedian portion of clypeus relatively narrowly inserted between frontal lobes; mandible long and straight, inserted in the middle of anterior margin of head; two or three apical teeth elongate and forming a fork; subapical tooth often present as an angle or small triangular tooth; masticatory margin edentate or serrate, ventrally with a row of several long setae; antenna 12-segmented, filiform; scape elongate, a little flattened in its apical part; eye usually developed well, but rarely reduced (consisting of less than 10 ommatidia); mesosoma in lateral view with a straight dorsal outline, or pronotum weakly raised dorsad; promesonotal suture completely separating pronotum and mesonotum; mesonotum sometimes raised as a transverse ridge; metanotal groove shallowly to moderately impressed, or indistinct dorsally; mesopleuron well defined dorsally and posteriorly by carinae and/or grooves; propodeal spines usually absent (but rarely present as small teeth); orifice of propodeal spiracle round; propodeal lobe absent; apicoventral part of foretibia usually with a small simple spur behind a large pectinate spur; apicoventral part of mid tibia with a simple spur in front of a simple to barbulate spur, with a single simple spure only, or without any spurs; apicoventral part of hind tibia with a simple spur in front of a large pectinate spur, or with a single pectinate spur only; petiole at most with a very short anterior peduncle; petiolar node in lateral view high, but not forming a single spinous apex; subpetiolar process developed well as a lobe; girdling constriction between abdominal segments III and IV usually inconspicuous; abdominal sternite III with a distinct anteroventral flange beneath helcium; sting well developed.

Differentiation. The worker of Anochetus is most similar to that of Odontomachus, but in the latter the posterior face of the head (inside preoccipital carina) has a pair of dark lines which meet together at or near the dorsalmost part of preoccipital carina, and the vertex has a median longitudinal carina which meet together at the dorsalmost part of the preoccipital carina.

Bionomics. Anochetus spp. usually occur in well-developed forests and other woody habitats. They nest in rotting logs and wood fragments, and in litter and soil.

Brachyponera
Morphology. Workers of Vietnamese species have the following features (see also Schmidt & Shattuck 2014): Worker monomorphic; body (excluding mesopleuron and metapleuron) covered with a dense fine pubescence, and sparsely with standing hairs; head in full-face view subrectangular; preoccipital carina inconspicuous dorsally and laterally; frontal lobes horizontal, relatively small, separated from each other just with a longitudinal sulcus; antennal scrobe absent; median portion of clypeus moderately convex, with anteromedian margin truncate or weakly concave; mandible triangular with ca. 8–10 teeth on masticatory margin; basal portion of mandible with a pit or groove dorsolaterally (but the pit/groove sometimes obsolete); antenna 12-segmented, gradually incrassate from segment III to XII; eye moderate in size, located on side of head relatively close to mandibular insertion; promesonotum forming a dome which is in lateral view distinctly higher than anterior border of propodeal dorsum; promesonotal suture completely separating pronotum from mesonotum; metanotal groove deeply impressed; mesonotum present as a distinct disc well margined anteriorly by promesonotal suture and posteriorly metanotal groove; mesopleuron separated well from mesonotum and metapleuron with distinct sutures, not divided by a transverse groove; propodeum unarmed; orifice of propodeal spiracle small and round; propodeal lobe almost absent; apicoventral part of foretibia without small simple spur behind a large pectinate spur; apicoventral part of mid and hind tibiae with a simple spur in front of a large pectinate spur; outer surface of middle tibia with normal pilosity only; petiole without anterior peduncle; petiolar node squamiform, in lateral view high and thin; subpetiolar process developed, anteriorly without a conspicuous round depression, posteroventrally with an acute angle or a pair of acute angles; girdling constriction between abdominal segments III and IV weak; anteroventral frange/carina of abdominal sternite III (prora) reduced and not externally visible; sting well developed.

Differentiation. The worker of Brachyponera is most similar to that of Pseudoponera, but the latter lacks the basal mandibular pits, deep metanotal groove, and raised promesonotal dome. The worker of small species of Brachyponera are most similar in general appearance to that of Hypoponera, but in the latter the apicoventral part of the mid and hind tibiae lacks a smaller, simple spur in front of the pectinate large spur.

Radchenko (1993a) described Brachyponera mesoponeroides from Vietnam (type locality: Cuc Phuong), and Bolton (1995) and Schmidt & Shattuck (2014) combined the species in Pachycondyla. However, Sk. Yamane’s examination of the type series suggests that the species belongs to Hypoponera. The problem will be solved in a future study.

Bionomics. Pachycondyla spp. usually occur in well-developed forests and other wooded habitats. They nest in rotting logs and wood fragments, and in litter and soil.

Buniapone
Morphology. Workers of Vietnamese species have the following features (see also Schmidt & Shattuck 2014):

Worker monomorphic; head in full-face view subrectangular; preoccipital carina almost absent; frontal lobes horizontal, separated from each other just with a longitudinal sulcus; antennal scrobe absent; anteromedian margin of clypeus forming a rectangular projection; mandible elongate-triangular, with 6–7 teeth on masticatory margin; basal portion of mandible with a narrow groove dorsolaterally; antenna 12-segmented, gradually incrassate from segment III to XII; eye extremely reduced (consisting of a few ommatidia), located before midlength of side of head in lateral view; promesonotum in lateral view slightly raised; promesonotal suture completely separating pronotum from mesonotum; metanotal groove absent; mesopleuron separated well from mesonotum and metapleuron with distinct sutures, not divided by a transverse groove; metapleural gland bulla, when seen through the sclerite, bean-shaped, large in size (the anterior margin of bulla reaching midlength of metapleuron); metapleural gland orifice opening posterolaterad, with anterior and posterior cuticular flanges; propodeum unarmed; orifice of propodeal spiracle oval; propodeal lobe present but very low; apicoventral part of foretibia with a small simple spur behind a large pectinate spur; apicoventral part of mid and hind tibiae with a simple spur in front of a large pectinate spur; outer surface of middle tibia without peg-like or spiniform setae among background pilosity (but relatively long and thick standing setae present among background pilosity; a few stout setae present near tarsus but never extending along length of tibia); petiole without anterior peduncle; petiolar node squamiform, in lateral view high and thin; subpetiolar process triangular; girdling constriction between abdominal segments III and IV weak; abdominal sternite III usually with a distinct anteroventral kiel beneath helcium; sting well developed.

Differentiation. The worker of Buniapone most closely resembles that of Centromyrmex, but in the latter eye completely absent, and the anteromedian margin of clypeus does not form a rectangular projection. The worker of Buniapone is also similar to that of Myopias, but in the latter metanotal grooves distinct dorsally, and petiolar node in lateral view thick.

Bionomics. Workers of Buniapone amblyops have been collected by digging up the ground in well-developed forests.

Centromyrmex
Morphology. Workers of Vietnamese species have the following features (see also Schmidt & Shattuck 2014):

Worker monomorphic; head in full-face view subtrapezoidal; frontal lobe horizontal, developed well, completely concealing antennal socket; antennal scrobe absent; anteromedian margin of clypeus weakly convex; posteromedian portion of clypeus narrowly inserted between frontal lobes; mandible elongate-triangular, with serrate masticatory margin; basal angle inconspicuous; basal portion of mandible without a distinct circular fovea or elongate depression dorsolaterally; antenna 12-segmented, gradually incrassate from segment III to XII; scape flattened basally; apical 4 segments somewhat flattened; eye absent; pronotum in lateral view angulate anterodorsally, flattened dorsally; promesonotal suture completely separating pronotum and mesonotum; anterior margin of mesonotum distinctly higher than posterior margin of pronotum; mesopleuron distinctly margined dorsally and posteriorly; metanotal groove absent, instead a distinct broad constriction separating mesonotum from propodeum; dorsum of propodeum in lateral view much lower than anterior part of mesonotum; propodeum unarmed; orifice of propodeal spiracle elliptical; propodeal lobe almost absent; forecoxa massive; outer surface of middle tibia and middle basitarsus with thickened peg-like setae mixed with the normal finer pilosity; apicoventral part of foretibia always with a simple spur behind a large pectinate spur; apicoventral part of midtibia with two simple spurs; apicoventral part of hind tibiae with a simple spur in front of a large pectinate spur; petiole with an anterior peduncle; petiolar node in lateral view somewhat cubic; subpetiolar process developed well as a penant-shaped lobe; girdling constriction between abdominal segments III and IV present but very weak; abdominal sternite III with an anteroventral U-shaped ridge; sting well developed.

Differentiation. The worker of Centromyrmex is most similar to that of Cryptopone, but in the latter the basal portion of the mandible has a distinct circular fovea or elongate depression dorsolaterally.

Proceratiinae
Key to Vietnamese Proceratiinae Genera