Taxonomy of the Leptogenys modiglianii species group from southeast Asia (Hymenoptera, Formicidae, Ponerinae)

Abstract Leptogenys breviloba sp. n., Leptogenys curva sp. n., Leptogenys itoi sp. n., Leptogenys kanaoi sp. n., Leptogenys malayana sp. n., and Leptogenys modiglianii Emery, 1900 are described from southeast Asia. The Leptogenys modiglianii species group is proposed on the basis of similarities among the six species. An identification key to species in this group from southeast Asia is provided.


Introduction
The genus Leptogenys Roger, 1861 is one of the largest ant genera, and contains 302 species and 25 subspecies throughout the tropical and subtropical regions (Bolton 2016). In the Oriental region, approximately 70 Leptogenys species have been described. They have not been comprehensively studied, although Xu and He (2015) provided a preliminary key to the known Oriental species. There are no species groups well defined on the basis of worker morphology in this region. Leptogenys modiglianii Emery, 1900  HW Head width: in full-face view, the maximum width of the head excluding the eyes. CML Clypeal median lobe length: in full-face view, the straight-line length measured from the anterior margin of the clypeus to the anterior margin of the torulus.

SL
Scape length: the straight-line length of the first antennal segment, excluding the neck and the basal condyle.

EL
Eye length: in full-face view, the vertical line length of the compound eye.

PrL
Pronotum length: in profile, the diagonal length of the pronotum, measured from the anterior margin of the pronotum excluding the collar to the posterior extremity of the pronotum. Weber's length: in profile, the diagonal length of the mesosoma, measured from the anterior margin of the pronotum excluding the collar to the posterior extremity of the propodeal lobe. PeL Petiole length: in profile, the maximum length of the petiole, measured from the anteriormost margin to the posteriormost margin of the petiole, including the peduncle. PeH Petiole height: in profile, the height of the node, measured from the apex of the subpetiolar process to the highest point of the node.
Description. In full-face view, head either longer than wide or almost as long as wide (CI: 77-101), broadening anteriad, widest just posterior to clypeus excluding eyes; posterior margin broadly convex. Mandible sickle-shaped, elongate, curved near base and becoming straight apically or curved throughout, without denticles, subapical tooth either absent or present near apical tooth; internal margin with narrow lamella; large gap present between mandibular shaft and clypeus; mandibles with only their apical portions crossing each other when fully closed. Eye large (OI: 26-39), situated just posterior to clypeus, breaking outline of lateral margin of head. Antennal scape almost as long as width of head or longer (SI: 99-121), surpassing posterior margin of head by one-sixth to two-fifths of its length; antennomere III longer than II; antennomere XII shorter than III, longer than XI. Anterior edge of torulus located anterior to mandible base. Clypeus short, with longitudinal median carina; anterolateral margin broadly concave, either with or without lateral lobe; apical median extension (CLI: 12-21) with convex or truncate apex, fringed by narrow translucent lamella, with pair of peg-like setae. Hypostomal teeth large, visible in full-face view. Pronotum in profile longer than high, in dorsal view shorter than wide or longer. Mesonotum in dorsal view shorter than wide. Metanotal groove distinctly visible, weakly to strongly impressed. Meso-metapleural sulcus present. In profile, propodeal dorsum convex to straight, posteriorly rounding into declivity, longer than length of propodeal declivity; metapleural-propodeal sulcus shallow. Petiole in profile longer than high or shorter (LPI: 94-118), in dorsal view longer than wide (DPI: 71-87); node in profile either rectangular (dorsal face subhorizontal) or fan-shape (dorsal face distinctly sloping anteriad), highest posteriorly, with anterior and dorsal faces forming continuous curve or anterior face of node ventrally vertical and dorsally forming continuous curve with dor- sum, in dorsal view widening posteriad, with lateral margin broadly convex; posterior face flat, abruptly separated from lateral face, slightly inclined anteriad. Subpetiolar process consisting of high anterior lobe and thin posterior extension; anterior lobe fan-shaped, with continuously curved anteroventral margin and concave posterior margin. Anterior face of gastral tergite I flat; in profile, anteroventral edge of gastral sternite I shallowly indented just posterior to prora; in profile, prora long-rectangular, low; constriction between gastral segments I and II distinct.
Head, mesosoma, and petiole mostly areolate-rugose, superimposed with small piligerous punctures. Antennal scape and legs densely punctuated. Clypeus with oblique to longitudinal striae. Propodeal declivity with transverse crests. Postgenal bridge and prosternum sparsely with circular depressions, medially smooth and without punctures. Mesosternum smooth and without punctures, sometime with transverse striate anteriorly and posteriorly. Ventrolateral and posterior faces of petiolar node smooth; subpetiolar process finely striate. Anterior face of gastral tergite I smooth; gastral segment I with scalloped depressions that are deepest anteriorly and sloping posteriad; segment II smooth or covered with scalloped depressions; constriction between gastral segments I and II finely scrobiculate; segments III-V smooth.
Body black and tinged with red, shiny. Hairs of various lengths, scattered, whiteyellow; long hairs standing; short pubescence decumbent; antenna and legs with dense short pubescence, mixed with scattered long hairs.
Queen (Figs 5,7,9,12). In general structure the queen is very similar to the worker (ergatoid queen) and lacks ocelli; it differs from the worker in having a higher and wider petiole (LPI: 105-132; DPI: 79-94) and voluminous gaster.
Key to species in the Leptogenys modiglianii species group from southeast Asia: worker 1 In profile, petiole longer than or almost as long as high (LPI: 94-102); dorsal face of node subhorizontal (Fig. 16A)  Worker. Diagnosis. In full-face view, head distinctly longer than wide (CI: 82-84). Mandible broadly curved throughout. Clypeus with lateral lobe, smoothly incurved between lateral lobe and median extension; apex of median extension convex. In profile, petiole longer than or almost as long as high (LPI: 94-102), highest near middle, with subhorizontal dorsal face.
Measurements ( Description. In full-face view, head distinctly longer than wide. Mandible broadly curved throughout, with subapical tooth near apical tooth. Eye strongly prominent, measuring one-third of head lateral margin length. Antennal scape distinctly longer than width of head, surpassing posterior margin of head by one-fourth of its length; antennomere III ca. 1.6 times as long as wide. Clypeus with lateral lobe, smoothly incurved between lateral lobe and median extension; median extension short, with convex apex. In dorsal view, pronotum shorter than or slightly longer than wide. Metanotal groove weakly impressed. In profile, propodeal dorsum almost straight. Petiole in profile longer than or almost as long as high, highest near middle, with subrectangular node; anterior face of node ventrally vertical and dorsally forming continuous curve with dorsum; dorsal face subhorizontal, but weakly sloping anteriad; posterior margin almost straight to slightly concave.
Head distinctly areolate-rugose. Mandible smooth. Gastral segment I with scalloped depressions, which are irregular in size but generally small; distance between small depressions greater than diameter of depressions; large depressions close to each other; segments II smooth.
Body black, slightly tinged with red; clypeus, mandible, antenna, legs and ventral half of petiole dark-red. Apical two or three segments of gaster red-brown. Scalloped depressions on gastral segments I bearing hairs.  Worker. Diagnosis. In full-face view, head distinctly longer than wide (CI: 77-78). Mandible distinctly curved throughout. Clypeus without lateral lobe; apex of median extension strongly projecting. In profile, petiole higher than long (LPI: 115-117), highest just anterior to posterodorsal angle; anterior and dorsal faces of node forming continuous curve; dorsal face distinctly sloping anteriad. Gastral segment II extensively covered with scalloped depressions. Body covered with understory layer of short, dense and recumbent pubescence.
Measurements ( Description. In full face view, head distinctly longer than wide. Mandible distinctly curved throughout, with subapical tooth near apical tooth. Eye prominent, measuring one-fourth to one-third of head lateral margin length. Antennal scape longer than width of head, surpassing posterior margin of head by less than onefifth of its length; antennomere III ca. 2.2 times as long as wide. Clypeus without lateral lobe; median extension moderately long, with apex strongly projecting. In dorsal view, pronotum longer than wide. Metanotal groove distinctly impressed. In profile, propodeal dorsum broadly convex. Petiole in profile higher than long, with fan-shaped node, highest just anterior to posterodorsal angle of node; anterior and dorsal faces of node forming continuous curve; dorsal face distinctly sloping anteriad; posterior face almost straight. Head weakly areolate-rugose, longitudinally striate anteriorly; vertex weakly and transversally striate. Mandible longitudinally striate. Prosternum weakly rugose. Gastral segments I-II extensively covered with scalloped depressions that are irregular in size and close to each other; generally depressions on segment I larger than those on segment II. Body black-gray; clypeus, mandible, antenna, legs, and ventral half of petiole darkred. Body covered with understory layer of short, dense and recumbent pubescence. Scalloped depressions on gastral segments I-II bearing hairs.   [SKYC]; 3 workers, 1 queen (FI11-16) 99-110), surpassing posterior margin of head by two-fifths to one-third of its length. Clypeus with lateral lobe, with blunt angle between lateral lobe and median extension; median extension long, with broadly convex apex. In profile, petiole distinctly higher than long (LPI: 109-118), highest just anterior to posterodorsal angle; anterior face of node ventrally vertical and dorsally forming continuous curve with dorsum; dorsal face distinctly sloping anteriad.
Measurements ( Description. In full face view, head slightly longer than wide. Mandible curved near base, becoming straight apically; subapical tooth obsolete. Eye prominent, measuring one-fourth to one-third of head lateral margin length. Antennal scape longer than width of head, surpassing posterior margin of head by two-fifths to one-third of its length; antennomere III ca. 2.5 times as long as wide. Clypeus with lateral lobe, with blunt angle between lateral lobe and median extension; median extension long, with broadly convex apex. In dorsal view, pronotum almost as long as wide. Metanotal groove slightly impressed. In profile, propodeal dorsum almost straight. Petiole in profile distinctly higher than long, highest just anterior to posterodorsal angle of node, with fan-shaped node; anterior face of node ventrally vertical and dorsally forming continuous curve with dorsum; dorsal face distinctly sloping anteriad; posterior face slightly concave dorsally and slightly convex ventrally.
Head strongly areolate-rugose, longitudinally striate near clypeus; vertex weakly and transversally striate. Mandible weakly striate longitudinally. Prosternum smooth and without punctures. Gastral segment I with scalloped depressions that are irregular in size; distance between depressions distinctly greater than diameter of depressions; interspace between depressions with small punctures; segments II smooth.
Body black, slightly tinged with red; clypeus, mandible, antenna, legs and ventral half of petiole dark-red. Apical two or three segments of gaster red-brown. Scalloped depressions on gastral segment I bearing hairs; small punctures without hairs.
Queen. Measurements (n = 5). HL: 1.58-1.68, HLL: 1.07-1.14, HLA: 0.10-0.14, HW: Description. In full-face view, head longer than wide excluding eyes, wider posteriorly; posterior margin distinctly rounded. Mandible small, without basal angle and Figure 10. Leptogenys itoi sp. n., paratype, male. A head, full-face view B lateral view C petiole, lateral view D dorsal view E forewing F hindwing. denticles, with rounded apex. Eye occupying over half of head length. Three prominent ocelli present; maximum length of lateral ocellus shorter than minimum distance between lateral ocellus and eye. Antenna 13-segmented; scape distinctly shorter than width of head; antennomere II shortest, roughly as long as wide; III longest; XIII shorter than III. Clypeus triangular and projecting anteriad, convex on midline; anterolateral margin straight; apex moderately acute; epistomal suture broadly rounded. Mesoscutum in profile convex, in dorsal view shorter than wide, widest posterior to mid-length; notaulus weakly notable; parapsidal line more than half of mesoscutal length; transscutal line almost straight. Anterior margin of mesoscutellar disc rounded.
In profile, propodeal dorsum forming continuous curve with declivity; metapleuralpropodeal sulcus present. Forewing ca. 3.0 times as long as wide, with stigma. Hindwing less than 0.8 times as long as forewing. Petiole in profile higher than long, in dorsal view longer than wide, highest posteriorly, with short peduncle, with fan-shaped node; anterior and dorsal faces forming convex line; dorsal face sloping anteriad; posterior face convex; in dorsal view, lateral margin broadly convex. With waist in profile, anterior lobe of subpetiolar process short-subtriangular, anterior margin convex, ventral apex moderately acute, posterior margin concave. With gaster in profile, prora low, long; continuously curved between prora and anteroventral edge of gastral sternite I. Constriction between gastral segments I and II distinct.
Head, mesosoma, and petiole weakly rugose, with piligerous small punctures. Mandible smooth. Clypeus with oblique to longitudinal striae. Subpetiolar process finely striate. Gastral segment I with irregularly sized depressions; distance between depressions distinctly greater than diameter of depressions; interspace between depressions with small punctures; segments II-V smooth; constriction between gastral segments I and II finely scrobiculate Body black, tinged with red; clypeus, mandible, antenna, legs, subpetiolar process, and gaster red-brown. Hairs of various lengths, scattered, white-yellow; antennal scape and legs with dense short pubescence, mixed with long scattered hairs. Scalloped depressions and small punctures on gastral segment I bearing hairs.

Leptogenys kanaoi sp. n.
http://zoobank.org/6E7E651D-FCEF-445A-A775-F44FB961D35D Figures 3, 11, 12 Worker. Diagnosis. In full-face view, head distinctly longer than wide (CI: 78-83). Mandible strongly curved throughout. Clypeus without lateral lobe; apex of median extension strongly projecting. Petiole in profile higher than long (LPI: 112-122), highest just anterior to posterodorsal angle; anterior face of node ventrally vertical and dorsally Description. In full face view, head distinctly longer than wide. Mandible strongly curved throughout, with subapical tooth near apical tooth. Eye prominent, measuring one-fourth to one-third of head lateral margin length. Antennal scape distinctly longer than width of head, surpassing posterior margin of head by one-fifth of its length; antennomere III ca. 2.2 times as long as wide. Clypeus without lateral lobe; median extension moderately long, with apex strongly projecting. In dorsal view, pronotum longer than wide. Metanotal groove distinctly impressed. In profile, propodeal dorsum broadly convex. Petiole in profile higher than long, highest near mid-length, with roughly fanshaped node; anterior face of node ventrally vertical and dorsally forming continuous curve with dorsum; dorsal face sloping anteriad; posterior face almost straight.
Head weakly areolate-rugose, longitudinally striate anteriorly; vertex weakly and transversally striate. Mandible weakly and longitudinally striate. Prosternum weakly rugose. Gastral segment I with scalloped depressions that are irregular in size and close to each other; segments II smooth.
Body black, gaster slightly tinged with red; clypeus, mandible, antenna, legs and ventral half of petiole dark-red. Apical two or three segments of gaster red-brown. Scalloped depressions on gastral segment I bearing hairs.
Queen Male. Unknown. Remarks. The colony (AK92), including the holotype, was collected from rotted wood. It was composed of four queens, nine workers, and two pupae. Detailed collecting locality of the types is unknown. For convenience, the location of this species is marked at the center of Trengganu Province, Malaysia, on the distribution map (Fig. 3).

Leptogenys malayana
Type locality. Trengganu, Malaysia. Distribution. Malaysia: Peninsular Malaysia (Trengganu). Worker. Diagnosis. In full-face view, head almost as long as wide (CI: 98-101). Mandible curved near base, becoming straight apically. Antennal scape distinctly longer than width of head (SI: 115-121), surpassing posterior margin of head by two-fifths of its length. Clypeus with lateral lobe, with blunt angle between lateral lobe and median extension; apex of median extension truncate. Petiole in profile distinctly higher than long (LPI: 112-116), highest just anterior to posterodorsal angle; anterior face of node ventrally vertical and dorsally forming continuous curve with dorsum; dorsal face distinctly inclined anteriad.
Measurements (  Description. In full face view, head almost as long as wide. Mandible curved near base, becoming straight apically; subapical tooth distinct in holotype or absent in paratypes. Eye prominent, measuring one-third of head lateral margin length. Antennal scape distinctly longer than width of head, surpassing posterior margin of head by two-fifths of its length; antennomere III ca. 2.7 times as long as wide. Clypeus with lateral lobe, with blunt angle between lateral lobe and median extension; median extension short, with truncate apex. In dorsal view, pronotum shorter than wide. Metanotal groove slightly impressed. In profile, propodeal dorsum weakly convex to almost straight. Petiole in profile distinctly higher than long, highest just anterior to posterodorsal angle, with fan-shaped node; anterior face of node ventrally vertical and dorsally forming continuous curve with dorsum; dorsal face distinctly inclined anteriad; posterior face slightly concave dorsally and slightly convex ventrally.
Head strongly areolate-rugose, longitudinally striate near clypeus; vertex weakly and transversally striate. Mandible distinctly striate longitudinally. Gastral segment I with scalloped depression that are irregular in size but generally large; large depressions close to each other; distance between small depressions greater than diameter of depressions; segments II smooth.
Body black, gaster slightly tinged with red; clypeus, mandible, antenna, legs and ventral half of petiole dark-red. Apical two or three segments of gaster red-brown. Scalloped depressions on gastral segment I bearing hairs.
Queen and male. Unknown. Worker. Diagnosis. In full-face view, head distinctly longer than wide (CI: 88-90). Mandible curved near base, becoming straight apically. Antennal scape slightly longer than width of head (SI: 103-105), surpassing posterior margin of head by one-fifth to one-fourth of its length. Clypeus with lateral lobe, smoothly incurved between lateral lobe and median extension; median extension with convex apex. In profile, petiole slightly higher than long (LPI: 103-108), highest just anterior to posterodorsal angle; anterior and dorsal faces forming continuous curve; dorsal face distinctly sloping anteriad.

Leptogenys modiglianii
Measurements (n = 5, lectotype in parentheses Redescription. In full-face view, head distinctly longer than wide. Mandible curved near base, becoming straight apically; subapical tooth absent. Eye prominent, measuring one-fourth to one-third of head lateral margin length. Antennal scape slightly longer than width of head, surpassing posterior margin of head by one-fifth    to one-fourth of its length; antennomere III ca. 2.3 times as long as wide. Clypeus with lateral lobe, smoothly incurved between lateral lobe and median extension; median extension moderately long, with convex apex. In dorsal view, pronotum longer than wide. Metanotal groove weakly impressed. In profile, propodeal dorsum almost straight. Petiole in profile slightly higher than long, highest just anterior to posterodorsal angle, with fan-shaped node; anterior and dorsal faces forming continuous curve; dorsal face distinctly sloping anteriad; posterior face almost straight but slightly convex.
Head weakly areolate-rugose, longitudinally striate anteriorly; vertex weakly and transversally striate. Mandible smooth. Gastral segment I with scalloped depressions that are irregular in size; distance between depressions distinctly greater than diameter of depressions; interspace between depressions with small punctures; segment II smooth.
Body black, slightly tinged with red; clypeus, mandible, antenna, legs and lower half of petiole dark-red. Apical two or three segments of gaster red-brown. Scalloped depressions on gastral segment I bearing hairs, small punctures without hairs.
Queen and male. Unknown.

Discussion
In the Oriental region, the members of the Leptogenys modiglianii species group are similar to those of the L. maxillosa species group, which includes two species, L. falcigera Roger, 1861 andL. pruinosa Forel, 1900 in the region. They share several features such as the elongate and curved mandible, anterior edge of torulus located anterior to mandible base, short clypeus, eye situated just posterior to clypeus and  breaking outline of lateral margin of head, hypostomal teeth visible in full-face view, petioler node subrectangular in profile, and subpetiolar process consisting of high anterior lobe and thin posterior extension. However, the L. modiglianii species group is distinguished from the L. maxillosa group by the following contrasting character states (maxillosa group in parentheses): clypeus with apical median extension (without median extension), body surface mostly areolate-rugose (with shagreened sculpture), and body extensively covered with standing hairs (without standing hairs). Mann (1919) indicated that L. modiglianii is related to four species in the Australian region: L. emeryi Forel, 1901from Bismarck Islands, L. foreli Mann, 1919from Solomon Islands, L. triloba Emery, 1901from New Guinea, and L. truncate Mann, 1919 from Santa Cruz Islands. These four species share the above diagnostic characters with the modiglianii species group defined in this paper and possibly belong to this species group.
There is little information about this species group. Most of the specimens examined in this study were collected in one place: Ulu Gombak on the Peninsular Malaysia. This species group may also occur in Java, Kalimantan, and Sulawesi, Indonesia, and additional as-yet undescribed species may be found in Sundaland and New Guinea.
This species group in southeast Asia is divided into three subgroups. One, which contains L. itoi, L. malayana and L. modiglianii, is recognized by elongate antennomere III that is ca. 2.3-2.7 times as long as wide (Fig. 15C), presence of the lateral lobe on the anterior margin of the clypeus (Fig. 17A), short petiole (LPI: 103-118), and fan-shaped petiolar node. The second group, which contains L. kanaoi and L. curva, is recognized by the strongly curved mandible, relatively short antennomere III that is ca. 2.2 times as long as wide, absence of the lateral lobe on the anterior margin of the clypeus (Fig. 17B), short petiole (LPI: 112-122), and fan-shaped petiolar node. Leptogeny breviloba is a remarkable species among this species group, with very short antennomere III that is ca. 1.6 times as long as wide (Fig. 15D), anterior margin of the clypeus with lateral teeth, long petiole (LPI: 94-102), and rectangular petiolar node.