Leptogenys modiglianii species group

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Based on: Arimoto, K. 2017. Taxonomy of the Leptogenys modiglianii species group from southeast Asia (Hymenoptera, Formicidae, Ponerinae). ZooKeys 651: 79–106 (doi:10.3897/zookeys.651.10366).

Species

Distribution

Malaysia (Peninsular Malaysia, Borneo), Indonesia (Sumatra, Engano Island).

Identification

Key to Leptogenys modiglianii species group workers

Worker Head widest just posterior to clypeus excluding eyes. Mandible sickle-shaped, elongate, without denticles. Anterior edge of torulus located anterior to mandible bases. Clypeus short, with apical median extension. Eye situated just posterior to clypeus, breaking outline of lateral head margin. Hypostomal teeth large, visible in full-face view. In profile, petioler node rectangular to fan-shape; subpetiolar process consisting of high anterior lobe and thin posterior extension. Body surface mostly areolate-rugose, extensively with standing long hairs.

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, presence of the lateral lobe on the anterior margin of the clypeus, 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, 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, anterior margin of the clypeus with lateral teeth, long petiole (LPI: 94–102), and rectangular petiolar node.

In the Oriental region, the members of the Leptogenys modiglianii species group are similar to those of the Leptogenys maxillosa species group, which includes two species, Leptogenys falcigera and Leptogenys pruinosa 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).

Description

Worker 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 dorsum, 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, white-yellow; long hairs standing; short pubescence decumbent; antenna and legs with dense short pubescence, mixed with scattered long hairs.

Queen 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.

Male Only known from L. itoi.

Notes

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.

Mann (1919) indicated that L. modiglianii is related to four species in the Australian region: Leptogenys emeryi from Bismarck Islands, Leptogenys foreli from Solomon Islands, Leptogenys triloba from New Guinea, and Leptogenys truncata from Santa Cruz Islands. These four species share the diagnostic characters with the modiglianii species group and possibly belong to this species group.