Leptogenys species groups

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Lattke 2011. Revision of the New World species of the genus Leptogenys Roger (Insecta: Hymenoptera: Formicidae: Ponerinae). Arthropod Systematics & Phylogeny 69:127-264.

These groupings of the New World Leptogenys are based on similarities in worker morphology.

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antillana species group

Worker diagnosis - Head subrectangular in full-face view; eye weakly convex, situated laterad at cephalic mid-length, eye longer than maximum scape width, circumocular sulcus well developed; scape surpasses posterior cephalic margin by not more than one-fourth its length, funicular segments with marked constrictions, third antennal segment longer than other basal funicular segments; suture between antennal sclerite and tentorial pit well impressed. Median clypeal lobe broadly triangular, with (L. antillana) or without (L. reggae) lamella, with or without apical setae; lateral lobe narrow; basal mandibular sulcus well impressed, basal and external mandibular margins subparallel. Mesosoma with promesonotum forming single broad convexity in lateral view; propleuron smooth and shining; mesonotum transverse; metanotal groove well impressed, smooth; metanotal-propodeal sulcus absent to weakly impressed propodeum unarmed; node longer than wide in dorsal view; cross-section of node at mid-length with convex sides; constriction between abdominal segments III and IV moderately to well developed; posterodorsal swelling of metacoxa well developed; pro- and metatibial apex without setae, mesotibial apex with single seta; body mostly smooth and shining, without appressed pubescence, scattered standing to decumbent hairs present on body.

Comments - The two known species from this group are island endemics, one found in Jamaica, and another in Hispaniola. The queens are still unknown in this group. The lack of propodeal lobes or teeth shown by L. antillana and L. reggae is rare within the pusilla clade, in which the phylogenetic analysis places this group.

Possible apomorphies - The lateral position of the eye on the head at cephalic mid-length is not seen in other species. The few species with eyes at cephalic midlength have the eyes dorsolaterally placed on the head.

arcuata species group

Worker diagnosis - Compound eyes dorsolaterally situated on head, diameter greater than one-fourth lateral cephalic margin; clypeal apex with setae, median clypeal lobe small, shorter than maximum scape width, with lamella; mandibles arched, narrow, and parallel-sided; suture between antennal sclerite and tentorial pit well impressed; labrum with scattered pointed tubercles on anterior face; well-developed hypostomal lobes usually present (except L. arcuata); PF: 4,4. Antenna with each funicular segment gradually expanding apicad, third antennal segment not noticeably elongate; mesonotum subquadrate to wider than long, never narrow and transverse; propleuron mosly transversely striate (smooth in L. arcuata), metanotal groove well impressed, scrobiculate; metapleural-propodeal suture present, propodeum unarmed; node with posterior margin vertical in lateral view, without an apical crest or point, posterior face of node flat, smooth and shining, posterior and lateral margins separated by sharp angle (except L. santacruzi); meso-, metapleuron, and most of lateral face of petiole rugulose; anterior face of abdominal segment III flat, subpetiolar process with sloping posterior margin in lateral view; constriction between abdominal segments III and IV weak; body without pubescence; head, mesosoma, petiole and gaster with scattered standing pilosity, no appressed pubescence. Metacoxal dorsum without swelling at base; apex of protibia lacking setae; apex of mesotibia with 1 external seta; apex of metatibia without setae.

Comments - These ants are found from southern Mexico into northern South America, including an island endemic on Santa Cruz, Galapagos Islands. One species, L. arcuata, may actually represent a complex with representatives in the Amazon watershed and the Lesser Antilles. No queens are yet known for this species group, even in species that have been relatively well sampled, such as L. arcuata or L. donisthorpei, leading to the inference that egg laying workers fulfill this reproductive role in the group.

Possible apomorphies - The reduced clypeal lobe, presence of clypeal setae, slender, arched mandibles, and large hypostomal lobes are synapomorphic with the unistimulosa group, the apparent sister group to the arcuata group. The arcuata group claims as apomorphic the flattened posterior face of the node that is separated from the rest of the node by a sharp edge, lacking the curvature usually associated with this margin. The disc of the anterior face of abdominal segment III is also flattened. There is a lack of pubescence on the head and mesosoma dorsum which could be considered apomorphic as the loss of pubescence is common for the pusilla clade, but not for taxa outside of it. The unistimulosa group retains pubescence on the cephalic dorsum, and occasionally presents sparse pubescence on the mesosoma.

crudelis species group

Worker diagnosis - Head longer than wide; eye diameter not more than one-third the length of lateral cephalic margin, eye weakly convex, dorsolaterally placed on head, circumocular sulcus absent; median clypeal lobe with lateral lamella, clypeal apex without setae, lateral clypeal lobe poorly developed; mandible shuts tight against clypeus, basal mandibular sulcus well developed, mandible subtriangular; sulcus between tentorial pit and antennal sclerite shallow, scape surpasses posterior cephalic margin by at least one-fourth its length; third antennal segment longer than neighboring basal funicular segments. Mesonotum wider than long, not narrow; metanotal groove smooth, not scrobiculate; metapleural-propodeal suture absent; declivitous propodeal margin shorter than dorsal margin in mesosomal lateral view, propodeum with lobe or tooth; node subtriangular (L. iheringi, L. vogeli) to subquadrate (L. crudelis) in lateral view, petiolar node longer than wide in dorsal view; anterodorsal margin of third abdominal segment convex in lateral view, constriction between abdominal segments III and IV well developed; metacoxa with low posterodorsal swelling; protibial apex lacking seta, mesotibial apex with single seta, metatibial apex with (L. crudelis) or without (L. iheringi) apical seta; body mostly with smooth and shining sculpture; appressed pubescence lacking, scattered standing hairs present on dorsum of body

Comments - This group has three member species, all of similar size and general appearance, in southeastern Brazil. Ergatoid queens are known for L. crudelis, and L. iheringi.

Possible apomorphies - This group needs more scrutiny to extract decent support. The absence of a circumocular sulcus is uncommon amongst New World Leptogenys, yet ascertaining the extent of presence or absence of this sulcus is not without difficulties. A smooth and polished cuticle will hinder clear observation, especially in smaller sized species even if a strip of mylar is used to diffuse the light source. The sulcus between the tentorial pit and antennal sclerite is quite shallow, and this is usually well impressed in most species.

elongata species group

Worker diagnosis - Head not subrectangular, lateral margins convex, posterolateral margins convergent. Mandible variable in shape, ranging from triangular to elongate and falcate, mandibular masticatory margin edentate, basal sulcus variably developed from shallow to deep; median clypeal lobe prominent, longer than ocular malar distance (except L. oaxaca, L. chamela); no setae on clypeal apex (except L. foraminosa); PF: 4,3. Eyes dorsolaterally situated on head; eye diameter usually between one-fourth and one-third the length of lateral cephalic margin in full face view, rarely more; scape surpasses posterior cephalic margin by over one-fourth its length, third antennal segment elongate compared with neighboring funicular segments; funicular segments sub cylindrical (except L. chamela, L. bifida); median clypeal lobe with lateral lamella; mesosoma with abundant sculpturing, not smooth and shining; propleuron transversely striate to rugulose; metanotal groove deeply impressed (variable in L. sianka), smooth or scrobiculate; mesonotum longer than wide to wider than long, never narrow and transverse; anteroventral carina weak to absent especially ventrad (distinct in L. volcanica, L. elongata); metapleural-propodeal suture weakly developed to absent; propodeum unarmed or with low lobes or teeth; propodeal spiracle mostly elongate to almost slit-shaped, sometimes oval, facing posterad (posterolaterally in L. bifida), followed posterad by sulcus; dorsal and declivitous propodeal margins form single convexity in lateral view; node subquadrate in lateral view; anterior margin of abdominal segment III mostly vertical and weakly convex; constriction between abdominal segments III & IV usually weak, moderate at best; dorsum of head, mesosoma, petiole, and at least gastral segments I – II with appressed pubescence and standing hairs; protibial apex lacking setae; apex of mesotibia usually with single seta (none in L. peninsularis, L. sonora); metatibial apex with 0 or 1 seta; metacoxa lacking basal swelling.

Comments - These are the New World Leptogenys with the northernmost distribution, including L. elongata found from northern Mexico to Texas and Louisiana (U.S.A.), and L. manni, found in Florida, U.S.A. Most species are found in Mexico and Central America with a few reaching northwestern Colombia. All are of moderate to large size. Besides species found in temperate climates, the group also has species endemic to arid localities such as L. sonora in the Sonoran Desert and L. peninsularis in the Baja Peninsula of Mexico, and in lowland and montane humid forests also. The extent of development of the propodeal armature can vary from distinct teeth to low lobes or entirely edentate (L. sonora, L. chamela, L. peninsularis, and L. manni). Within L. elongata, the lobes may vary in development. The propleuron is usually mostly smooth and shining in this genus with sculpturing limited to the periphery, but the elongata species bear rough sculpturing throughout this sclerite and on most of the head and mesosoma as well. This is also accompanied by the presence of pubescence on the head and mesosoma. The trend in many groups seems to be towards smooth and shining sculpturing, and loss of pubescence. Ergatoid queens are known for several species in this group.

Possible apomorphies - A good number of plesiomorphies provide uniting criteria for this collection of species, where the only possible apomorphy detected so far seems to be the weakening and effacement of the anteroventral mesopleural carina, especially ventrad. This carina is normally well-defined in this genus. Noise is produced by two exceptions to this within the group and by the lack of this carina in L. panops, an incertae sedis species with enough characters to place it closer to the arcuata-unistimulosa lineage, safely away from the elongata species.

famelica species group

Worker diagnosis - Head elongate; mandible triangular, masticatory and basal margins approximately of same length, shuts tight against clypeus, masticatory margin concave, totally to partially serrate, with pre-apical tooth at mid-length; basal mandibular sulcus weakly impressed; median clypeal lobe mostly laminate and translucent against background lighting, lobe shorter than ocular malar distance, lacking setae on apex; PF: 4,3. Suture between antennal sclerite and tentorial pit well impressed; eyes dorsolaterally to laterally placed on cephalic dorsum; eye diameter ranging from over one-third to under one-fourth length of lateral cephalic margin in full-face view; scape long, surpassing posterior cephalic margin by over one-third its length, third antennal segment much longer than other basal funicular segments, funicular segments subcylindrical; clypealantennal base protrudes prominently dorsad in lateral view (except L. famelica); propleuron smooth and shining (except some L. famelica); mesonotum wider than long to longer than wide, never narrow and transverse, metanotal groove deeply impressed, usually smooth, sometimes with transverse striae or weakly scrobiculate; mesosoma mostly smooth (except L. famelica); mesopleuron abruptly elevated along mesometapleural suture, anteroventral carina well developed, anteriorly elevated in shape of lobe or fin; metapleural-propodeal suture absent; propodeum without low lobes or teeth, rounded (in L. famelica a low overhang may be present); propodeal spiracle facing laterally to posterolaterally, propodeal spiracle on same level as surrounding cuticle; scattered hairs present on dorsum of head, mesosoma, petiole and gaster; cephalic dorsum with scattered pubescence, none on mesosomal dorsum; dorsal and declivitous propodeal margins form continuous convexity in lateral view; petiolar node triangular to subquadrate; anterior margin of third abdominal segment in lateral view convex; postpetiolar constriction weak; protibial apex without setae; mesotibial apex with single seta; metatibial apex with single seta (L. famelica, L. pinna) or no seta (L. phylloba, L. pittieri, L. serrata); posterobasal metacoxal dorsum with weak swelling.

Comments - The five members of this group are found from Costa Rica southward to the Amazon watershed. L. famelica has the largest range of all, with records from Costa Rica to the Amazon watershed, whilst the other species apparently have much smaller distribution ranges. The size range of these ants is from quite large to median sized, there are no small species. Whilst the general trend in the genus has been towards more slender mandibles and an edentate masticatory margin, this group retains the generalized triangular shape with a serrated masticatory margin. With the exception of the large and conspicuous L. famelica, there is scarce museum material belonging to this group, hinting to the relative rarity of these species. An example is L. pittieri, a species known only from the type material and even though the type locality has been the object of many ant collecting activities, no other specimens have been found. Worker reproduction seems to be the situation for L. famelica, whilst ergatoid queens are known for L. pinna and L. pittieri. Several specimens clearly belonging to this group where studied but none could be satisfactorily assigned to the recognized species, and given that all were uniques, it was decided to determine each as famelica group members. The species in this group seem to form a compact set with L. famelica as the odd-man out. Besides the conspicuously larger size of L. famelica, it lacks the dorsally elevated frontal lobes when seen laterally, a feature seen in the other members of the group. During preliminary runs of diverse versions of the character matrix, L. famelica, and two other species in the group were considered as terminal taxa. Good support for the monophyly of the 3 species was recovered with L. famelica as sister to the other two species.

Possible apomorphies - The mostly translucent median clypeal lobe and the well-developed anterior lobe of the mesopleural carina are the proposed autopomorphies for the group. This anterior lobe projects perpendicularly from the lateral mesopleural surface, like a small fin, in all species save L. famelica. The antennae have an elongate third segment and the funicular segments are subcylindrical, but these same character states can be found in other New World Leptogenys.

ingens species group

Worker diagnosis - Compound eyes tending to dorsolateral position with head in full-face view, eyes large and convex, diameter usually ranging from one-fourth to one-third the lateral cephalic margin in full-face view, occasionally more or less; scape surpasses posterior cephalic margin by at least half its length; third antennal segment elongate, median clypeal lobe and lateral clypeal lobes well developed, median lobe with slight basal kink (except L. ingens) and no setae on apex nor fringing lamella; deep transverse sulcus present along posterior clypeal margin between anterior tentorial pit and anterior margin of antennal sclerite; mandible elonpeal spiragate, not triangular, with pre-apical notch, basal sulcus well impressed; PF: 4,3. Third antennal segment elongate; mesonotum wider than long to longer than wide, never narrow and transverse; metanotal groove weakly to moderately impressed, never scrobiculate; metapleural-propodeal suture weakly impressed; propodeum unarmed, profile rounded, dorsum with transverse striae (striae weak in L. tiobil); propodeal spiracle elongate; petiolar node shape usually subquadrate (triangular in L. tiobil) in lateral view, apex of node with tooth or blunt lobe; body with abundant erect hairs, appressed pubescence present on cephalic and mesosomal dorsum; mesosoma well sculpted, not smooth and shining; body color black, with or without blue iridescence; constriction between abdominal segments III and IV moderate; protibia with 1 – 3, usually 2, setae on posterior face just basad of strigil; apex of mesotibia with 1 (2 in L. ingens) seta on external face; apex of metatibia with 1 external seta (L. ingens in addition with 1 – 2 internal apical setae); metacoxal dorsum with low posterobasal swelling; subpetiolar process abruptly projected, not tapering; posteriorly concave in lateral view.

Comments - This group of relatively large and easily recognizable species has a distribution limited to the northern South American Coastal Range, from northeastern Venezuela to northern Colombia, including Margarita Island, but none reported yet from Trinidad. The most widespread species is L. ingens. L. carbonaria is known only from the Santa Marta Cordillera in northern Colombia. Reproduction is apparently by egg-laying workers as numerous nests found and collected have failed to reveal any specimen that could be recognized as a queen using external morphology alone.

Possible apomorphies - A strong apomorphy supporting monophyly of this group is the presence of setae on the protibia just basad of strigil insertion, and also, but a bit weaker is the discrete kink of the median clypeal lobe. A posterior process on the petiolar node is also found in the species of the unistimulosa group.

langi species group

Worker diagnosis - Head capsule subrectangular in full-face view; eye length greater than maximum scape width, eye convex to weakly convex, situated weakly dorsolaterally on head; mandible elongate, basal and external margins subparallel, basal mandibular margin with 2 – 3 stout hairs (not setae), mandibular basal sulcus well impressed, mandible leaves open space between basal margin and clypeus, does not shut tight; frontoclypeal suture shallow but well-defined; median clypeal lobe slender, length greater than basal width, apex sharply pointed, lacking apical seta; scape surpasses posterior cephalic margin by under one-fourth its length; basal funicular segments subequal in length. Mesonotum wider than long in mesosomal dorsal view; metanotal groove scrobiculate (L. minima, L. mavaca) or smooth (L. langi); metapleural-propodeal suture absent; propodeal spiracle facing posterolaterad with depressed area between spiracle and bulla; propodeum armed with low blunt tooth. Petiolar node longer than wide in dorsal view, anterior margin greater than half width of posterior margin, node subquadrate in lateral view; constriction between abdominal segments III & IV weak (L. mavaca) to moderately developed (L. minima, L. langi); sculpturing on dorsum of head, thorax, and abdomen mostly smooth and shining with standing pilosity, no pubescence present (except cephalic dorsum of L. minima); anterior margin of abdominal segment III vertical to weakly convex; tibial apices lacking seta; metacoxal tumosity well developed.

Comments - The three small sized species known from this group are distributed within the Amazon-Orinoco watershed. L. langi is the most collected and apparently the most widespread, whilst the other two species are known from a single series each. The basal funicular segments in L. langi tend to have a marked constriction between each while the segments are subcylindrical in the other species, with a weak constriction between each segment. The gap between the mandibles and clypeus is greatest in L. langi, but narrow in the other two species. One of the few species of Leptogenys with winged queens is L. langi. During the final stages of studying material for this revision at least two possible species apparently related to at least one or two of the species listed here were found. Since they are only represented by single specimens it was decided not to describe them. With the accumulation of much more specimens than at hand now hopefully additional characters may be gleaned for satisfactorily defining not only species limits but how these species are related to each other. The phylogenetic analysis placed L. langi as close to L. antillana. Clearly more work is needed here.

Possible apomorphies - This is a very weakly supported group without an explicit apomorphy. The possible apomorphies can be found in various other groups: eye weakly dorsolaterad on head, mandible does not shut tight against clypeus, internal mandibular margin with 2 – 4 stout hairs, median clypeal lobe elongate and slender, shortened scape, antennal segments with strong constriction, and mesotibial apex lacking setae.

luederwaldti species group

Worker diagnosis - Head elongate, eye much larger than maximum scape width (OI > 0.29), eye dorsolaterally situated on head, its diameter covering at least one-fourth to over one-third of lateral cephalic margin; third antennal segment quite elongate compared with surrounding segments, funicular segments subcylindrical without marked constrictions between each; scape extends beyond posterior cephalic margin by one-third its length (except L. pucuna); mandible shuts tight against clypeus when closed, mandibular shape subtriangular tending to elongate with parallel to subparallel basal and external margins, basal mandibular margin without basal convexity; basal sulcus deeply impressed (except L. linda); sulcus between basal antennal sclerite and tentorial pit shallow but well-defined; labrum with scattered piligerous tubercles on anterior face; median clypeal lobe longer than ocularmalar length, with lateral lamella, lacking setae on apex; PF: 4,4 (L. cuneata, L. gaigei) or 4,3 (L. imperatrix, L. luederwaldti). Propleuron mostly smooth; mesonotum wider than long to longer than wide, never narrow and transverse; metapleuralpropodeal suture absent to indistinct; mesosoma mostly smooth and shining (except L. imperatrix); metanotal groove well impressed (shallow in L. gaigei), not scrobiculate; propodeal spiracle elongate to broadly oval; cross-section of petiolar node at mid-length V-shaped, node triangular to semi-triangular in lateral view, rounded margin between posterior and lateral face; cuneiform in dorsal view with narrow, peduncular anterior part (except L. linda); anterior margin of abdominal segment III in lateral view convex, continuous with dorsal margin; propodeal declivity rounded and unarmed (L. imperatrix, L. cuneata) or weakly concave with lateral tooth (L. luederwaldti, L. gaigei, L. linda). Constriction between abdominal segments III and IV modest to absent; metacoxal dorsum with weakly developed posterobasal swelling; apex of protibia lacking setae (L. cuneata sometimes with 1 seta); apex of mesotibia with 1 external seta (L. cuneata with 1 – 2 internal additionally); apex of metatibia without seta (except L. cuneata with one internal seta); body with sparse, standing hairs and appressed pubescence on head only (on whole body in L. imperatrix, absent in L. luederwaldti); body sculpture mostly smooth and shining (punctate in L. imperatrix); blue iridescence present on body (L. luederwaldti, L. gaigei, L. cuneata, L. imperatrix) or absent.

Comments - These large to medium sized species are found from Honduras into the Amazon watershed, except for L. luederwaldti which is found in southeastern Brazil. The propodeum may be armed with teeth or lobes as in L. luederwaldti, L. linda, L. pucuna, and L. gaigei, or it may lack any trace of armature as in L. imperatrix and L. cuneata. The postpetiolar constriction may be well marked as L. imperatrix, L. linda, and L. pucuna; or it may be poorly marked as in L. cuneata, and L. gaigei. L. gaigei and L. cuneata share a translucent lobe next to the protibial strigil. Ergatoid queens are known for three species but L. gaigei may reproduce through gamergates as it is a fairly well collected species and no distinct queens have been recovered to date. In preliminary phylogenic analyses, L. gaigei, L. imperatrix and L. luederwaldti were separately considered and they were recovered as a group.

Possible apomorphies - The wedge-shaped petiole in dorsal view, with a very brief anterior margin compared with the posterior margin, and concave lateral margins, besides the triangular to subtriangular shape in lateral view is what distinctly sets this group apart from the others.

maxillosa species group

Worker diagnosis - Head broader than long, compound eyes dorsolaterally situated on head, diameter greater than maximum scape width; sulcus between basal antennal sclerite and tentorial pit well impressed; median clypeal lobe broadly triangular, bordered by narrow translucent lamella that extends laterad beyond lateral margin of antennal fossa to mid-point between clypeal apex and mandibular insertion; two setae present on clypeal apex; lateral clypeal lobe indistinct; mandible smooth and shining, slender, except for basal curve, arching and tapering apicad; apex of hypostomal tooth visible in cephalic full-face view; anterior face of labrum with a anterior series of transverse crests that form an irregular arch, without scattered tubercles; scape extends beyond posterior cephalic margin by less than one-fourth its length; antennal segments II – VI narrower basad than apicad, segments beyond of uniform diameter; antennal segment III not noticeably longer than other segments; metanotal groove weakly impressed in lateral view, not scrobiculate; mesometapleural suture weakly impressed, metapleural propodeal suture obsolete; propodeum unarmed, laterally broadly angular; node in lateral view subquadrate with a brief posterior shelf, sides convex, ventral process shaped as en elongate triangular anterior lobe; cross-section of petiolar node at mid-length convex; constriction between abdominal segments III and IV well developed. Cuticle opaque and dominated by rough to fine pruinosity; fine, appressed pubescence present throughout body, dorsum of body without standing hairs except on gastral apex, and scattered hairs on cephalic and gastral ventrum. Apex of protibia with single stout seta; apex of mesotibia and metatibia without setae; metacoxal dorsum with posterobasal low swelling.

Comments - This is a group native to Africa that includes several tramp species (Bolton 1975), of which only L. maxillosa is known from the New World, though L. falcigera could be present. Superficially L. maxillosa resembles a wheeleri group species, especially on account of similarities in the cuticular texture, lack of standing hairs, and slender mandibles, but a number of characters suggest this to be convergence. The median clypeal lobe in the wheeleri group does not extend laterad beyond the antennal fossa, and the lateral lobe is distinct; the clypeal apex lacks setae such as those in L. maxillosa. The mandibles in L. maxillosa are very smooth, whilst the mandibles in the wheeleri group show some fine striae. The shagreened appearance of the cuticle in L. maxillosa is construed by fine areolae or rugulae, with occasional sparse punctae; the shagreening in L. wheeleri is based on fine punctuation, without larger punctures or other features. The protibial apex has a short stout seta on the external side in L. maxillosa, a feature lacking in wheeleri species. The subpetiolar process in L. maxillosa appears as an elongate triangle in lateral view, with a long slope, whilst in the wheeleri group the process is short and abrupt. The mandibular basal sulcus in L. maxillosa is rough and contrasts with the rest of the smooth mandible, whilst the sulcus in the wheeleri group is smooth. The base of funicular segments II – VI in L. maxillosa are of a lesser diameter basad than apicad, contrasting with the regular diameter of all the funicular segments in the wheeleri group. The posterior margin of the petiolar node of L. maxillosa in lateral view has a modest shelf, a feature lacking in the wheeleri group species, and the prora protrudes anterad more than in the wheeleri group.

pusilla species group

Worker diagnosis - Head rectangular in full-face view, lateral cephalic margin broadly convex, head widest at eyes (except L. corniculans, and L. glabra), eye weakly dorsolaterad to laterally placed on head; eye length longer (except L. corniculans, L. pusilla, L. ritae) than maximum scape width, eye broadly to weakly convex, ommatidia tend to become fused; at least one mandible shuts tight against clypeus, mandibular basal and external margins subparallel, basal mandibular margin with low convexity at base (weak in L. quadrata) upon which are 2 – 4 setae, basal mandibular sulcus well developed; median clypeal lobe slender, without apical setae; lateral lamella of median clypeal lobe absent or very narrow, poorly developed; PF: 4,4. Basal funicular segments subequal in length, the third antennal segment frequently weakly longer than neighbouring segments, scape surpasses posterior cephalic margin by under one-fourth its length; suture between basal antennal sclerite and tentorial pit well impressed; mesonotum transverse, narrow; metanotal groove fine, shallow, smooth, not scrobiculate (except L. guianensis); mesometapleural suture well impressed, scrobiculate; metapleural-propodeal suture absent; dorsal propodeal margin at least 2 × longer than declivitous margin in lateral view; propodeum laterally bluntly angular or armed with blunt lobe (distinctly triangular in L. corniculans), declivitous face with transverse striae, spiracle faces posterolaterad (laterad in L. guianensis); node subquadrate in lateral view; cross-section of petiolar node at mid-length V-shaped to subparallel, not convex; node longer than wide in dorsal view; anterior margin of abdominal segment III vertical, flat to weakly convex, dorsal margin convex in lateral view; constriction between abdominal segments III and IV well developed; exoskeleton mostly smooth and shining; no appressed pubescence present; sparse standing hairs present on dorsum of body; metacoxal dorsum with well-developed posterobasal swelling; mesotibial apex with or without single apical seta.

Comments - The mostly small to medium sized species of this group range from southern Mexico south into Colombia, eastern Ecuador and Venezuela into the Amazon Basin and the Mata Atlantica. Towards the end of this study specimens representing unknown species of this group from southern Mexico were supplied by John Longino. The queens are ergatoid, with or without the greatly swollen, yellow mandibles in L. josephi, L. pusilla, and L. ritae. In L. glabra the head is widest anterad. Found mostly in humid forests but some species have been recorded from dry forests (L. ritae) or from arid thorny brush vegetation (L. cf. gorgona) on Santa Cruz Island of the Galapagos Archipelago. Several specimens representing what could be distinct species were seen during the course of this study but they were not pursued any further than a species group determination given the scant material involved. At least one form has a scrobiculate metanotal groove. This is a difficult group with uncertainties about the extent of morphological variability and how this affects discernment of species limits. The node cross-section in L. ritae and L. guianensis is not as clearly V-shaped since it tends to be weakly convex dorsad, but overall it is not a convex section but the specialised queens shared by L. ritae and L. josephi point to membership in this group. The trend towards fusion of the ommatidia is evidenced by a loss of convexity for each ommatidium, with the separation between each reduced to a fine line as if a hot iron had partially flattened the eye. All species show this either totally or partially for each eye. This modification of the lens is best developed in the rufa species group where a single lens seems to cover the reduced compound eyes.

Possible apomorphies - The elongate mandibles with the basal margin bearing a broad concavity at the base, followed apicad by a convexity, along with the presence of 2 – 4 setae basad along the basal mandibular margin define this group from other New World species. Setae or thickened hairs on the inner mandibular margin have apparently developed a number of times in the New World fauna, but the sinusoidally shaped basal mandibular margin is distinctive for this assemblage of species. Other derived traits for this group is the shortened scape, transverse mesonotum, well-developed constriction between abdominal segments III and IV, and well-developed constriction between each antennal segment. But several instances of the presence of these traits will be found in other New World Leptogenys.

quiriguana species group

Worker diagnosis - Head subrectangular in full-face view; eye flattened, situated close to middle of head and weakly dorsolaterally, eye extending more laterad; eye without circumocular sulcus, eye length greater than maximum scape width; apex of median clypeal lobe with single median hair, plus two lateral hairs, no apical setae (except L. orchidiodes with weak seta), median clypeal lobe with or without lamella; median clypeal lobe broadly triangular (slender in L. gagates); suture between tentorial pit and basal antennal sclerite weakly impressed; mandible shuts tight against clypeus (except L. gagates), mandibular basal sulcus moderately to well developed, mandible usually with subparallel basal and external margins, less frequently subtriangular or triangular, basal mandibular margin lacking basal convexity, with 2 – 4 stout hairs; PF: 4,3. Scape surpasses posterior cephalic margin by not more than one-fourth its length; basal funicular segment longer than wide, neighboring segments subequal in length, funiculus weakly incrassate (except L. yocota). Body mostly smooth and shining, propleuron smooth and shining; metanotal groove relatively shallow, smooth, not scrobiculate; mesonotum wider than long in dorsal view, rectangular to narrow and transverse; promesonotal and dorsal propodeal margin relatively at same level in lateral view; propodeal spiracle oval to round, laterally to posterolaterally facing, without distinct sulcus from spiracle to metapleural bulla (except L. deborae, L. gagates, and L. yocota); declivitous margin shorter than dorsal margin, dorsal margin weakly convex to straight; propodeum with lobe or tooth (except L. erugata); metapleural-propodeal suture absent; mesosomal dorsum with sparse standing hairs and no appressed pubescence; no pubescence on cephalic dorsum; petiolar node subquadrate in lateral view; postpetiolar constriction weak to moderate; metacoxal dorsum with moderate posterobasal swelling; pro- and metatibial apex with no apical setae; mesotibial apex with single apical seta.

Comments - Most of these ants are distributed from Central America into northern South America along the Cordillera de la Costa of Venezuela except for L. nigricans and L. amu, both known from the Amazon watershed. Both L. yocota and L. amu have the compound eye situated more dorsolaterally on the head, while in the rest of the species it extends laterad. The mesonotal width is not more than twice its length in most species except L. amu. Almost all of these ants have fine standing hairs on the mesosoma except L. yocota which has noticeably stouter hairs than the rest. Ergatoid queens are known for this group, besides the only other known winged queen for the New World species, or at least a queen with the mesosomal sclerites associated with flight (L. nigricans).

Possible apomorphies - Apparently derived characters for this species are the flattened compound eye, mandible with 3 – 4 stout hairs along the inner margin, shortened scape, and the apex of the median clypeal lobe with a thick median hair flanked by two lateral hairs of lesser diameter. Most of these characters can be also found in other taxa, but the configuration of the hairs on the apex of the median clypeal lobe seems to be unique to these species.

rufa species group

Worker diagnosis - Head subquadrate; sulcus between antennal basal sclerite and tentorial pit well developed; scape surpasses posterior cephalic margin by not more than one-fourth its length (slightly longer in L. toxeres), basal funicular segments subequal in length, wider apicad than basad; lateral clypeal lobe modest, median clypeal lobe broad, not longer than maximum scape width, apex blunt except for median apical denticle, or bluntly angular, lacking apical setae; basal and external mandibular margins semiparallel, basal mandibular margin with row of hairs; mandibular sulcus shallow to well impressed; mandible does not shut tight against clypeus, but leaves noticeable gap; PF: 4,3 (unknown for L. toxeres). Eye diameter less than maximum scape width, reduced number of ommatidia, eye laterally to weakly dorsolaterally placed on head, lens of each ommatidium relatively indistinct, a single lens apparently covering all; mesonotum transverse; metanotal groove moderately to well impressed, scrobiculate; metapleural-propodeal suture present or absent; shallow sulcus present posterad of propodeal spiracle; propodeum armed with triangular lobe; node wider than long in dorsal view, subquadrate in lateral view; anterior margin of third abdominal segment vertical in lateral view; constriction between third and fourth abdominal segments moderate; appressed pubescence lacking on head, mesosoma, node and most of gaster; abundant standing pilosity present on dorsum of head, and mesosoma; body sculpturing ranges from punctate, foveolate, or sulcate to smooth and shining; metacoxal posterobasal swelling moderate to well developed; pro and metatibial apices lacking setae, mesotibial apex with single seta.

Comments - The members of this group are known from lowland sites from northeastern Mexico southwards into Costa Rica along the Gulf of Mexico and Caribbean coasts. Apparently rare as known from only three (possibly four) species, of which the suspect fourth species is only known from a single specimen. Queens are not yet known for this group.

Possible apomorphies - The configuration of the median clypeal lobe, apex blunt or truncate except for a median apical denticle, is not found in other New World Leptogenys. In L. toxeres this is not as apparent as its median lobe is broad but the apex ends in blunt angle. Other characters such as the reduced eye, in diameter as well as number of ommatidia, and the loss of distinct margins for each lens, which tend to become fused, a single lens apparently covering all the eye; basal mandibular margin with row of setae; mesonotum transverse; and worker node wider than long in dorsal view are found scattered throughout other New World Leptogenys.

unistimulosa species group

Worker diagnosis - Compound eye dorsolaterally placed on head, eye subglobulose and prominent, OI > 0.24 (except L. peruana); hypostomal lobe well developed, usually visible in full-face view of head (short in L. amazonica, L. peruana, and L. punctaticeps); 2 – 6, sometimes more, stout setae present on clypeal apex, median clypeal lobe reduced, not wider than maximum scape width, with narrow lateral lamella; mandible slender and elongate; labrum with scattered denticles on anterior face; PF 4,4; suture between antennal sclerite and tentorial pit well impressed; cephalic dorsum with pubescence (except L. amazonica); scape surpasses posterior cephalic margin by at least one-third its length; funicular segments subcylindrical, each segment slightly widening apicad, third antennal segment elongate; mesonotum either as long as wide, or longer than wide in dorsal view; propleuron mostly striate to rugulose (mostly shining in L. amazonica and L. peruana) metanotal groove well impressed, not scrobiculate; metapleural-propodeal suture present; mesosomal sculpture mostly striate to costulate, with sparse smooth and shining areas, pubescence lacking; propodeal dorsum transversely striate (tending to smooth in L. amazonica and L. peruana), propodeum unarmed; petiolar apex with a posteriorly directed tooth or lobe (except L. peruana) either sharply pointed or blunt; petiolar posterior margin sinuous in lateral view, with brief dorsal concavity and longer ventral convexity; petiolar sides convex in anterior view; constriction between abdominal segments III and IV modest; body with abundant standing hairs, appressed pubescence only on cephalic dorsum, occasionally on mesosomal dorsum, none on petiole nor gaster; apex of protibia lacking setae; apex of mesotibia with 1 external seta; apex of metatibia with a single seta (setae not discernible in L. amazonica); metacoxal dorsum without posterobasal swelling.

Comments - The members of this group are found mostly in South America, with some representatives in Central America and a species complex widespread in the Caribbean. They are all medium sized Leptogenys, even the smallest species: L. amazonica and L. peruana. Some of the more widespread species for the genus are in this group such as L. unistimulosa, found throughout northern South America southwards into Bolivia and Brasil, and the Caribbean-centered pubiceps complex of species. Reproduction is most probably through egg-laying workers as no morphologically distinct queens have been found to date amongst the species of this group.

wheeleri species group

Worker diagnosis - Compound eye dorsolaterally placed on head, diameter several times greater than maximum scape width, circumocular sulcus well impressed; sulcus between basal antennal sclerite and tentorial pit well impressed; clypeal median lobe bordered by narrow translucent lamella, lacking setae on apex, not longer than maximum width of scape; mandible slender, tends to falcate or subtriangular, none triangular, basal sulcus well impressed; anterior face of labrum with scattered low piligerous tubercles; PF: 4,3. Third antennal segment noticeably longer than rest of basal funicular segments, remaining funicular segments of uniform diameter, without marked constriction between each antennomere; integument densely shagreened or punctulae, opaque; no standing hairs on dorsum of head, mesosoma and abdominal segments I – IV, appressed pubescence present throughout body. Metanotal groove distinctly impressed, deep to moderate, not scrobiculate; propodeal spiracle facing posterad; propodeal declivity unarmed; metapleural-propodeal suture shallow; petiole with convex lateral margins in transverse cross-section; subpetiolar process anteriorly place, triangular or lobe like in lateral view, with convex posterior face. Apex of protibia lacking setae; apex of mesotibia with 1 – 2 external setae (none in L. maya); apex of metatibia with 1 external seta (none in L. maya). Constriction between abdominal segments III and IV modest, metacoxal dorsum without basal swelling.

Comments - This group is found from Mexico to Central America and is very easy to distinguish on account of the opaque pruinose integument that lacks standing hairs and the slender falcate or semifalcate mandibles. They superficially resemble species of the African maxillosa group, which has at least one tramp member in the American Tropics (see “Comments” for the maxillosa group for differences between the two groups) Males examined in L. wheeleri, L. maya. The examined males share a prominent shelf formed by the pronotal posterior margin and anterior mesonotal margin visible in lateral view. Ergatoid queens are known for this group.

Possible apomorphies - The densely shagreened and opaque integument, lack of standing hairs on the dorsum of the head, mesosoma, and abdomen are found in no other New World species. Possible apomorphies - This group shares with its postulated sister species, the arcuata group, reduced clypeal lobes; presence of clypeal setae; slender, arched mandibles; and large hypostomal lobes. All species have a posterior facing lobe or point on the node apex, a trait only shared with the ingens group. The distinctive apomorphy is the sinusoidal posterior margin of the petiolar node when seen in lateral view, no other New World species outside of this group show the trait.