Leptogenys

Identification
Leptogenys species groups (New World species)

Lattke (2011) - The apparent monophyly of Leptogenys is nowadays not questioned, probably due to several outstanding characters that qualify as apomorphies when compared with other ponerines. Besides the traditional pectinate claws and carinate median clypeal lobe, additional characters useful for separating this genus from other Ponerini may be considered: the presence of a basal protarsal comb is common in the most Ponerini, but is lost in Leptogenys. In Pachycondyla impressa the anterior tentorial pit is located close to the antennal sclerite whilst in Leptogenys it is quite separated. The tentorial pit in Myopias has a similar location to Leptogenys, and the two also share the presence of a median clypeal lobe and basal mandibular sulcus. The clypeal lobe in Myopias is usually subquadrate to rectangular, thicker and opaque throughout when compared with Leptogenys. Additionally there are Myopias species lacking the lobe, all suggesting this lobe is not homologous for the two groups. Presence of the basal mandibular sulcus is considered a plesiomorphic character (Schmidt 2009, in thesis). The relative situation of the tentorial pit should studied in other ponerines.

Nomenclature

 *  LEPTOGENYS [Ponerinae: Ponerini]
 * Leptogenys Roger, 1861a: 41. Type-species: Leptogenys falcigera, by subsequent designation of Bingham, 1903: 52.
 * Leptogenys senior synonym of Microbolbos: Wilson, 1955b: 136.
 * Leptogenys senior synonym of Dorylozelus: Taylor, 1969: 132.
 * Leptogenys senior synonym of Machaerogenys, Lobopelta: Bolton, 1975a: 240.
 * Leptogenys senior synonym of Odontopelta: Snelling, R.R. 1981: 390; Taylor & Brown, D.R. 1985: 32.
 * Leptogenys senior synonym of Prionogenys: Taylor, 1988: 33.
 * DORYLOZELUS [junior synonym of Leptogenys]
 * Dorylozelus Forel, 1915b: 24. Type-species: Dorylozelus mjobergi (junior secondary homonym in Leptogenys, replaced by Leptogenys tricosa), by monotypy.
 * Dorylozelus junior synonym of Leptogenys: Taylor, 1969: 132.
 * LOBOPELTA [junior synonym of Leptogenys]
 * Lobopelta Mayr, 1862: 733. Type-species: Ponera diminuta, by subsequent designation of Bingham, 1903: 54.
 * Lobopelta subgenus of Leptogenys: Forel, 1892k: 520.
 * Lobopelta revived status as genus: Dalla Torre, 1893: 43; maintained as genus: Bingham, 1903: 54.
 * Lobopelta junior synonym of Leptogenys: Emery, 1896e: 177 (footnote)
 * Lobopelta revived from synonymy as subgenus of Leptogenys: Forel, 1899c: 18; Forel, 1900d: 304; maintained as subgenus: Wheeler, W.M. 1910g: 135; Emery, 1911d: 101; Forel, 1917: 238; Wheeler, W.M. 1922a: 653; Creighton, 1950a: 50; Kempf, 1972a: 131.
 * Lobopelta junior synonym of Leptogenys: Bolton, 1975a: 240.
 * MACHAEROGENYS [junior synonym of Leptogenys]
 * Machaerogenys Emery, 1911d: 100 [as subgenus of Leptogenys]. Type-species: Leptogenys truncatirostris, by original designation.
 * Machaerogenys junior synonym of Leptogenys: Bolton, 1975a: 240.
 * MICROBOLBOS [junior synonym of Leptogenys]
 * Microbolbos Donisthorpe, 1948f: 170. Type-species: Microbolbos testaceus, by original designation.
 * Microbolbos junior synonym of Leptogenys: Wilson, 1955b: 136.
 * ODONTOPELTA [junior synonym of Leptogenys]
 * Odontopelta Emery, 1911d: 101 [as subgenus of Leptogenys]. Type-species: Leptogenys turneri, by monotypy.
 * Odontopelta junior synonym of Leptogenys: Taylor & Brown, D.R. 1985: 32.
 * PRIONOGENYS [junior synonym of Leptogenys]
 * Prionogenys Emery, 1895g: 348. Type-species: Prionogenys podenzanai, by monotypy.
 * Prionogenys junior synonym of Leptogenys: Taylor, 1988: 33.

Lattke (2011) - The genus Leptogenys as presently defined stems most recently from Bolton’s (1975) revision of the fauna from the Ethiopian Region and Madagascar. The generic worker diagnosis given below was taken using only New World species into account, and comparing with Bolton (1975). In a revisionary study of the ponerine genera based on molecular markers, Schmidt (2009, in thesis) found unequivocal molecular evidence for grouping Leptogenys along with 17 other genera into a monophyletic entity called the Odontomachus group, mostly of Old World distribution but with many species of Leptogenys, Anochetus and Odontomachus present in the New World. Within this group, Myopias is considered sister to Leptogenys, with evidence for both genera constituting one part of the basalmost divergence in the group, and the remaining genera the other part. Schmidt (2009, in thesis) argues for an Old World diversification of the Odontomachus group with age estimates ranging from 22 – 40 my according to diverse constraints, with a preferred estimate of 30 (38 – 24) my. The major radiations in Leptogenys have occured with an estimated crown age of 32 my (Schmidt 2009, in thesis). Examination of a few random Paleotropical species show character states not seen in New World Leptogenys such as a heavily dentate mandible, scale-like petiole, frontal lobe covering almost all of the antennal condyle or a moderately convex anterior clypeal margin. At least some traits are arguably plesiomorphic, thus lending a bit of morphological support to Schmidt’s conclusions based on molecular data

Worker
Lattke (2011) New World worker description.

Head shape ranges from elongate to wider than long in full-face view; vertexal carina present, usually visible from cephalic full-face view; compound eye usually situated anterad of mid-cephalic length, occasionally at mid-length, usually dorsolaterally situated on head; eye diameter may be very reduced, just a few ommatidia, to very large and prominent, its length covering more than one-third the lateral cephalic margin with the head in full-face view. Mandible variously shaped, either triangular or subtriangular, frequently elongate with subparallel internal and external margins, also falcate and incapable of closing against clypeus; masticatory margin usually shorter than basal margin, generally edentate or nearly so; rarely masticatory margin crenulate or with series of blunt denticles; apical tooth usually present, mandible usually with laterobasal sulcus. Clypeus relatively long with median portion of clypeus projecting anterad as distinct, variously shaped, usually triangular lobe, with a median longitudinal crest extending from apex to level of frontal lobes, clypeus extends briefly posterad between frontal carinae as narrow wedge; clypeus with narrow carinae or lobe bordering anterolateral cephalic margin; frontoclypeal suture straight and transverse, tentorial pit closer to compound eye than to antennal sclerite. Labrum frequently with tubercles on external face; palp formula 4,4 or 4,3. Frontal lobe covers less than half antennal insertion, frontal carinae very brief; antennae 12-segmented, usually weakly incrassate; scape usually surpasses posterior cephalic margin, rarely shorter; funicular segments subcylindrical or moniliform.

Propleural lateral and ventral face separated by curvature, not carinate; pronotum never with carinate sides; mesopleuron with anepisternum and katepisternum usually indistinctly separated; propodeal spiracle separated from declivitous margin in lateral view by at least 3 diameters; mesopleural carinae usually distinct, sometimes weakly developed, especially ventrad; pronotal suture mobile; mesonotum always distinct; metanotal groove distinctly impressed, from shallow and fine to deep and wide, smooth or scrobiculate; mesometapleural suture distinct, scrobiculate, posterodorsal edge of mesopleuron forming a distinct ledge; metapleural-propodeal suture varies from indistinct to well impressed. Propodeum with or without lateral teeth or lobes, declivitous face usually with broad transverse sulcus next to insertion of postpetiole.

Posterior face of anteroventral petiolar process medianly concave; prora well developed, usually shaped as transverse crest or lobe; gaster usually smooth and shining, sometimes abdominal segments III – IV punctate; pretergite of abdominal segment IV with stridulitrum; constriction between abdominal segments III and IV ranging from weakly developed to well developed; pygidium with or without longitudial crest; hypopygidium usually with a row of small setae. Tibiae without setae on lateral or dorsal surface; protibial apex usually without setae apicad of insertion of strigil (except L. panops); first protarsal segment without comb of stout setae opposite strigil; strigil without velum at base (except L. gaigei and L. cuneata); mesotibial apex usually with one small seta on external face, sometimes absent or several setae present; metatibial apex usually lacking apical setae; claws usually pectinate (this state is reduced in minute species such as L. pusilla or L. gorgona with few or no preapical teeth), arolium absent; meso- and metatibial apex each with 2 apical spurs. General body color ranges from black to ferruginous; mandibles, clypeus, antennae, legs, and gastral apex usually lighter colored than head, mesosoma, and gaster; blue or purple opalescence present in some species; sculpture varies from smooth and shining to striate, or punctate.

Additional References

 * [[Media:Lattke 2011.pdf|Lattke, J. E. 2011. Revision of the New World species of the genus Leptogenys Roger (Insecta: Hymenoptera: Formicidae: Ponerinae). Arthropod Systematics and Phylogeny 69:127-264. [2011-12-13] PDF]]