Malagasy Leptogenys species groups

These groups and key are based on Rakotonirina, J.C. & Fisher, B.L. 2014. Revision of the Malagasy ponerine ants of the genus Leptogenys Roger (Hymenoptera: Formicidae). Zootaxa 3836, 1-163.

Key to groups
Identification key to species groups of the workers of Malagasy Leptogenys

1

 * In full-face view, mandible either subtriangular or elongate but capable of closing tightly against the anterior margin of clypeus without a gap between them . . . . . 2


 * In full-face view, mandible elongate and narrow, not capable of closing tightly against the clypeus; the apices slightly crossing each other and leaving a large gap between themselves and the clypeus when closed . . . . . 7

2
return to couplet #1
 * With gaster in profile, prora generally globular and usually voluminous, directed anteroventrally; anteroventral angle of third abdominal sternite rounded; helcium usually situated almost to mid-height of anterior margin of third abdominal segment; prora and anteroventral angle of third abdominal sternite separated by large indentation . . . . . toeraniva group


 * With gaster in profile, prora flattened and small and directed ventrally along a vertical line; anteroventral angle of third abdominal sternite angulate; helcium situated at lower level near the anteroventral angle of third abdominal segment; prora and anteroventral angle of third abdominal sternite not separated by large indentation . . . . . 3

3
return to couplet #2
 * In full-face view, greatest width of eye roughly equal to or less than the greatest width of antennal scape; small species (HW: 0.60–0.83, PW: 0.59–0.70) . . . . . fiandry group


 * In full-face view, greatest width of eye markedly greater than the maximum width of antennal scape; generally larger species (HW: 0.75–1.92, PW: 0.60–1.62) . . . . . 4

4
return to couplet #3
 * Distance between anterior level of torulus and anteromedian margin of clypeus distinctly less than the distance between outer margin of torulus and outer margin of base of the mandible; mandible elongate and narrow; anterior clypeal margin widely transverse, broadly rounded or convex, usually bordered with white yellowish lamellae . . . . . truncatirostris group


 * Distance between anterior level of torulus and anteromedian margin of clypeus equal to or greater than the distance between outer margin of torulus and outer margin of base of the mandible; mandible short and robust, subtriangular or with convex inner margin; anterior clypeal margin medially projecting into a triangular lobe, edge sharp or bordered with subopaque lamella . . . . . 5

5
return to couplet #4
 * Dorsum of head and mesosoma smooth apart from piligerous pits . . . . . attenuata group


 * Sculpture on dorsum of head and pronotum variable, ranging from densely reticulate-rugulose, densely reticulate punctulate or densely punctulate to scattered punctures or punctulate . . . . . 6

6
return to couplet #5
 * Inner margin of mandible, at about mid-length, with angulate convexity; in profile, posterolateral margin of petiolar node with-out denticle or blunt angle, dorsum of pronotum either finely reticulate-rugulose or transversely finely striate-rugulose . . . . . mayotte and incisa groups (in part - also )


 * Inner margin of mandible without convexity at mid-length; in profile, posterolateral margin of petiolar node with small tooth, denticle or blunt angle; sculpture of the dorsum of head and mesosoma not the same as above . . . . . 

7
return to couplet #1
 * In full-face view, eye diameter usually less than the greatest width of antennal scape; mandible short and more or less straight . . . . . Leptogenys rabebe


 * In full-face view, eye diameter markedly greater than the maximum width of antennal scape . . . . . 8

8
return to couplet #7
 * Dorsum of head, mesosoma, petiolar node, and abdominal segments III and IV without standing hairs, but strongly shagreened and covered with dense pruinose pubescence . . . . . maxillosa group


 * Dorsum of at least some parts of the body covered with standing hairs, not strongly shagreened and not densely covered with pubescence . . . . . 9

9
return to couplet #8
 * Third antennal segment approximately twice as long as the second; dorsum of head smooth apart from scattered punctures; pronotum dorsally weakly sculptured; constriction between third and fourth abdominal segments indistinct . . . . . stuhlmanni group


 * Third antennal segment less than twice as long as the second; dorsum of head and mesosoma very strongly sculptured; gaster noticeably constricted between third and fourth abdominal segments . . . . . incisa group (in part - also )

attenuata group
In full-face view, mandible subtriangular, inner margin distinctly convex or with a blunt basal angle and closing tightly against anterior margin of clypeus; apical portions just superimposed when at rest; basal groove broadly impressed. Head shape variable but generally elongate and slightly broadened anteriorly. Eye most often large, maximum diameter greater than widest portion of antennal scape. Clypeus with median carina; anteriorly projecting medially into triangular lobe, lobe anterior margin with or fringed by semi-translucent lamella at least on apex; median clypeal carina elongate and sharp. Antennal scape long, at least 1/4 of its apical portion surpassing posterior margin of head. Propodeal declivity either transversely striate or smooth and shining. Petiole variable in width and length, but node generally longer than broad in dorsal view; in profile, posterior margin of petiolar node without small tooth or denticle. Helcium located roughly at anteroventral angle of third abdominal segment. Constriction between third and fourth abdominal segments slightly visible. Dorsum of head, mesosoma, petiolar node, and gaster entirely smooth and shining apart from small piligerous punctures. The attenuata group includes at least two complexes of closely related species. One complex, which includes Leptogenys angusta, Leptogenys johary and Leptogenys zohy, can be separated by the very long petiolar node (LNI: 49–77), which is strongly constricted anteriorly in dorsal view, and the presence of a long third antennal segment, which is at least twice as long as the second segment. The second species complex, which contains the remaining10 species, is characterized by a much shorter petiolar node (LNI: 77–121) with a slightly constricted anterior portion, and the average length of the third antennal segment is less than twice the length of the second.

fiandry group
Head rectangular, only slightly broadened in front of eyes. Eye either small or large, if small then maximum width less than greatest width of antennal scape. Anterior clypeal margin projecting medially into triangular lobe borderedby semi-translucent lamella. Mandible short and falcate, capable of closing tightly against clypeus; basal groove deeply impressed; blades slightly increasing in width from base to apical third and becoming narrow toward apical sharp tooth; preapical tooth inserted at apical third portion; inner margin with narrow and thin translucent lamella. Antennal scape relatively short, only one-fifth of its length extending beyond posterior cephalic margin; third segment apparently as long as the fourth. Metanotal groove strongly impressed, without transverse striation. Propodeal lobe indistinct. With petiolar node in lateral view, anterior margin much shorter than posterior; anterior margin rounding into the dorsum, which joins posterior margin at an apparently distinct angle. Helcium at anteroventral angle of third abdominal segment. Constriction between third and fourth abdominal segments visible. Dorsum of head and mesosoma mostly smooth and shining apart from scattered hair-bearing punctures or covered with fairly dense and fine punctures. Mandible smooth or longitudinally striate. Mesopleuron and lower half of sides of propodeum most often finely microrugulose. Propodeal declivity transversely striate. Light brown hairs and pubescence present on body. Integument with glossy reflection, blackish-brown to light brown in color, with lighter apical portion of gaster and appendages. This group consists of four species, recognized generally by their smaller body size, smaller eye and the presence of dense and fine reticulate-rugae or reticulate punctures on mesopleuron and lower half of lateral propodeal surface.

incisa group
Mandible elongate and narrow, with sharp apical tooth; usually not capable of closing tightly against clypeus, only their apical portions crossing each other when fully closed; very seldom are their inner margins convex and very seldom do they close tightly without a gap against the clypeus when at rest. Mandibular inner margin with narrow subopaque lamella; preapical tooth may be present near sharp apical one; basal groove narrow, vestigial or almost effaced. Head variably shaped, either subrectangular, ovoid or trapezoidal; head can be short and broad or narrow and elongate; posterior margin generally straight. Eye large, diameter greater than maximum width of antennal scape; either breaking or in front of outline of lateral border of head. Antennal scape with at least apical third surpassing posterior cephalic margin. Clypeus diversely shaped, projecting anteriorly into broad triangular lobe or apically terminated into toothlike spine, with a narrowly circular or obtusely triangular extension; translucent or semi-translucent lamella bordering clypeal margin, sometimes very narrow and barely visible in a few specimens; median clypeal carina long and usually sharp except for Leptogenys imerinensis. With mesosoma in dorsal view, metanotal groove with a straight or curved suture; posterior of metanotal groove, an additional suture present, dividing mesosoma into a fourth section. Propodeal lobe toothlike if present. In profile, petiole nodiform, either roughly as long as high, or longer than high. Constriction between third and fourth abdominal segments weakly to strongly visible. Dorsum of head, mesosoma and petiolar node lacking smooth areas, most often densely and finely reticulate-rugose, superimposed with small punctures. Erect or suberect hairs present on dorsum of head and rest of body, generally with sparse pubescence. Integument black to dark brown, with lighter coloration on apex of appendages. One of the largest species groups of Leptogenys from the Malagasy region, the incisa group contains 17 species that can be divided into three species complexes: the alluaudi, imerinensis, and voeltzkowi. The alluaudi complex includes Leptogenys alluaudi, Leptogenys incisa and Leptogenys pilaka, characterized by the absence of peg-like setae projecting anteriorly on the anteromedial clypeal margin and by its larger size. The voeltzkowi complex, with Leptogenys voeltzkowi, Leptogenys vitsy and Leptogenys sahamalaza, is distinguished by the presence of peg-like setae on the anterior margin of the clypeus and the restriction of a membranous spot to the small and rounded median lobe of the clypeus. The imerinensis complex contains the rest of the species and can be recognized by the broadly triangular or spine-like shape of the anteromedial clypeal lobe, which is equipped with at least one pair of peg-like setae. The incisa group is among the species-rich groups that show remarkable morphological variations within species. Populations within species sometimes show more variation than groups among species. In the present study, complexes of phenotypic divergences have been found based on mandible shape, the form of the anterior clypeal margin and the shape of the petiolar node. All of these species occur only in Madagascar except Leptogenys gracilis, one of the smaller species within the species group, which is also found on the Comoros Islands.

maxillosa group
Mandible narrow, long and curved with relatively broadly concave inner margin; not able to close tightly against clypeus; preapical tooth or denticles either absent or present and situated near sharp apical tooth. Head broadened anteriorly; sides slightly convex. Anteromedian clypeal margin projecting into obtusely angulate lobe and covered with a translucent fringing lamella median clypeal carina short. Eye large, maximum diameter noticeably greater than maximum width of scape. Antennal scape exceeding posterior cephalic margin by one fourth of its length. With mesosoma in dorsal view, metanotal groove weakly noticeable and not impressed. Constriction between abdominal segments III and IVdistinctly visible. Entire body densely and finely reticulate-rugulose to densely and finely reticulate-punctate, interspersed with larger punctures. Standing hairs absent from dorsum of body and first three abdominal segments, but long hairs only present on anterior border of clypeus and on mandibular blades. Whitish-yellow pubescence very dense all over the body. Integument black, with tip of gaster and apices of appendages brown.

saussurei group
Mandible short and robust, subfalcate, capable of closing tightly against median lobe of the clypeus; inner margin convex and covered with semi-translucent lamella, which becomes more transparent and broader from broadest width of blades towards apex; basal groove narrowly impressed. Head shape variable among species, but lateral borders not strongly diverging anteriorly and posterior margin straight. Clypeus broadly triangular anteriorly, with anteromedian lobe rounded or bidentate; median clypeal carina long and sharp. Eye large, maximum diameter greater than widest portion of antennal scape. Antennal scape relatively long. With mesosoma in profile, posterolateral margin of propodeum equipped with toothlike lobe at level of propodeal spiracle, whose opening may be elliptical or slit-like. In lateral view, petiolar node longer than high; vertical anterior margin slightly shorter than sloping posterior, which may have a sharp tooth, denticle or blunt tubercle at mid-height. Subpetiolar process simple, consisting of anterior hook-like teeth or a tubercle; a convex surface may be present posteriorly. Helcium at lower level in profile, located at anteroventral angle of third abdominal segment. Prora small and anteroventral angle of third abdominal sternite angulate; prora and anteroventral angle of third abdominal sternite not separated by large indentation. Gaster not constricted between first and second segments. Clypeus longitudinally rugulose, with sparse punctures. Dorsum of head, mesosoma and petiolar node variably sculptured, mostly with large, sparse punctures grading to smaller, dense ones; head in front of the level of eye longitudinally rugulose or striate; mesosoma and node of petiole seldom with rugulation. Standing hairs present; pubescence sparse or absent. Body color black to reddish-black, with bases of appendages dark brown which becomes orange-brown at the apices and gastral apex. In this species group, ergatoid queens are not known and the data indicate that the species may reproduce by mated workers.

stuhlmanni group
With only one species recorded from the Malagasy region, the species group description coincides with the species description.

toeraniva group
Mandible short, with convex inner margin; blades widest at about distal half or apical third and capable of closing tightly against clypeus; basal groove distinctly impressed; preapical tooth or denticle present near the broadly lamellate apical tooth. Clypeus bordered laterally with large lobe, anterior margin projects anteriorly into triangular median lobe, which is bordered with a semi-translucent lamella; two to three peg-like setae are present near anterior margin of median lobe of the clypeus; median clypeal carina long and sharp. Head apparently subrectangular; sides almost straight throughout their length and rounding into posterior cephalic margin. Eye usually small, with their greatest diameter less than the maximum width of antennal scape. With mesosoma in dorsal view, mesonotum broader than long; metanotal groove strongly impressed with cross-ribs or only consisting of a line; in profile, opening of propodeal spiracle rounded. Petiolar node variously shaped, either about as long as high or longer than high in profile; dorsal margin convex or straight; anterior and posterior faces at the same height or posterior face at lower level so that the node is inclined posteriorly; subpetiolar process consisting of anteriorly broad tooth followed by posterior rounded lobe with an indentation between them. Prora voluminous and lobe-like; anteroventral angle of third abdominal sternite usually rounded. Prora and anteroventral angle of third abdominal sternite separated by large indentation. Constriction between abdominal segments III and IV absent or very weakly visible. Body variously sculptured, but generally in dorsal view promesonotum and node of petiole with sparse punctures and propodeum rugulose interspersed with coarser punctures. In profile, mesopleuron, lateral section of propodeum and petiolar node, and anterior half of third abdominal segment either rugulose with sparse punctures or densely to typically punctate. Standing, erect, yellowish hairs and little pubescence present. Most species in this species group are cryptic and rarely collected. They exhibit a high degree of local endemism.

truncatirostris group
Mandible elongate and variably curved, but capable of closing tightly against clypeus; preapical tooth may be present; basal groove narrow. Head either strongly broader anterad than posterad or width changing very slightly along sides. In full-face view, eye may be small, greatest width slightly greater than widest part of scape, medium, with width about one and a half times the maximum width of scape, or large, with width at least twice as great as maximum diameter of scape; slightly convex and may or may not break the outline of lateral margin of head. Clypeus without a prominent projecting median lobe, anterior margin broadly evenly rounded or truncated and widely transverse; median longitudinal carina either present or absent. Distance between anterior level of antennal insertion and anteromedian margin of clypeus distinctly less than the distance between outer margin of torulus and outer margin of base of mandible. With mesosoma in dorsal view, metanotal groove impressed, with transverse striation; propodeal declivity transversely striate. With petiole in lateral view, node approximately as high as broad; dorsum convex and anterior face shorter than sloping posterior border. Gaster constricted between first and second segments. Sculpture of body mostly reticulate-rugulose, superimposed with small punctures, rarely with faintly effaced sculptures or scattered punctures. Three complexes of closely related species can be distinguished within the truncatirostris group on the basis of the shape of the mandible and the characteristics of the clypeus. First is the arcirostris complex, consisting of Leptogenys alatapia, Leptogenys arcirostris, and Leptogenys borivava, which can be separated from other complexes by the presence of the median longitudinal carina on the clypeus, a particularly short clypeus whose anterior margin is wide and broadly convex, and the superimposition of the mandibular blades when tightly closed against the anterior clypeal margin. The second is the ridens complex, represented by Leptogenys fotsivava, Leptogenys namoroka, Leptogenys ridens and Leptogenys tsingy, that can be identified by the presence of the median longitudinal carina on the clypeus, the rounded clypeus, and the fact that the mandibles cross each other when tightly closed against the anterior clypeal margin. Finally there is the truncatirostris complex, including Leptogenys diana and Leptogenys truncatirostris, for which the clypeus is anteriorly truncate or broadly rounded and lacks a median longitudinal carina, in profile mandibular blades bend forward so that their bases are inserted in a distinct angle relative to the head dorsum, then strongly curved down nearly at basal third, the blades widest at distal half and gradually narrower toward the sharp apical tooth, the interior margin of blades broadly arch from the distal half to the apex, and the surface from distal half to apex has dense and fine striae. Based on the collection records from the ant surveys in Madagascar, members of the truncatirostris species group may not have ergatoid queens, perhaps relying on mated workers instead.