Leptogenys sianka

This species has been found nesting in the epiphyte bromeliad Aechmea bracteata in Yucatan and was misidentified as Leptogenys mexicana (= Leptogenys elongata) in Dejean et al. (1995) and Dejean & Olmsted (1997). This same species was also the subject of studies on its predatory behavior by Dejean (1997), where he detected the attraction of bathytropid isopods directly into the ant nest.

Identification
Lattke (2011) - Cephalic dorsum mostly areolate, areolae turning to longitudinal to oblique striae-rugulae anterad of eye; mandible elongate, external and basal margins subparallel; metanotal groove shallow but distinct; smooth sulcus extends posterad from spiracle dorsad of bulla into propodeum.

This species can be confused with Leptogenys elongata on first sight but the mandibles permit easy separation as they are distinctly triangular in L. elongata.

A member of the elongata species group.

Distribution
This taxon is known from southeastern Mexico.

Castes
Male unknown.

Nomenclature

 *  sianka. Leptogenys sianka Lattke, 2011: 164, fig. 21 (w.q.) MEXICO.

Worker
Metrics, holotype (paratypes, n = 4): HL 2.00 (1.70-2.00); HW 1.45 (1.25-1.45); ML 1.15 (1.00-1.10); EL 0.45 (0.40-0.45); SL 2.20 (1.75-2.15); PW 1.25 (1.05-1.25); WL 3.25 (2.65-3.25); PH 1.15 (1.00-1.15); PL 1.00 (0.90-1.00); DPW 0.70 (0.60-0.70) mm. CI 0.73 (0.71-0.74); MI 0.79 (0.76-0.80); OI 0.31 (0.31-0.32); SI 1.52 (1.40-1.48); LPI 1.15 (1.11-1.15); DPI 0.70 (0.63-0.70).

Head sub-quadrate in full-face view, slightly wider anterad than posterad; lateral margin anterad of eye straight, posterad broadly convex; posterior cephalic margin straight to broadly convex; median clypeal process tapers to lamellate bluntly pointed apex; lateral clypeal process narrow, its outline smoothly joining with outline of median process. Eye broadly convex, situated slightly dorsad at mid-length, occupies over one-third of lateral cephalic margin. Cephalic dorsum mostly areolate, areolae anterad of eye becoming longitudinal to oblique striae-rugulae, small smooth patch present lateroposterad of frontal carina, clypeus with oblique striae, smoother medially; longitudinal sulcus extends posterad from between frontal carinae to one-third eye height. Scape densely punctulae, with dense decumbent pilosity and scattered subdecumbent hairs, scape extends beyond posterior cephalic margin by one-third its length; third antennal segment over 3 x longer than apical width, second antennal segment more than half length of third segment; fourth antennal segment almost half length of third segment, each funicular segment slightly wider apicad than basad. Mandible elongate, external and basal margins subparallel, weakly expanding apicad, with fine weak longitudinal strigulae and sparse punctae; chewing border edentate, corner with blunt angle; PF: 4,3.

Mesosoma with shallow, but distinct metanotal groove in lateral view that separates promesonotal margin and dorsal propodeal margin, both broadly convex; pronotal sculpture mostly areolate, posterolaterally with small rugulose patch; propleuron with longitudinal to oblique mostly parallel striae; mesonotum wider than long. Mesometapleural suture well impressed; metapleural-propodeal suture obliterated; propodeal spiracle elongate, opening directed posteriorly, smooth sulcus extends posterad from spiracle dorsad of bulla into propodeum; bulla of metathoracic spiracle round, prominent; mesopleuron mostly transversely strigulate anterad with rugulae posteroventrad and oblique to longitudinal strigulae anterad, low anteroventral carina developed anterad, absent posterad; rugulae on propodeal dorsum mostly transverse with striae close to petiolar insertion; metapleuron punctulate-strigulate, declivitous face transversely strigulate, rounding to lateral propodeal face, not separated by sharp ridge; propodeum with low irregular lobe at spiracle height; propodeal dorsum with shallow longitudinal sulcus; mesonotum broader than long in dorsal view, anterior margin convex; metanotal groove straight to convex, smooth; anterodorsal margin of mesopleuron with triangular smooth and shining patch. Propodeal spiracle elongate, almost slit-shaped.

Petiole sub-quadrate in lateral view, higher posterad than anterad; anterior margin more than one-half height of posterior margin, anterior margin straight, anterodorsal margin convex, posterior margin weakly convex to straight. Subpetiolar process shaped as curved lobe in lateral view, posterior margin concave. Node elongate in dorsal view; anterior margin convex, more than half width of posterior margin; posterior margin straight; lateral margin straight to weakly concave. Posterior face rounds to lateral face; lateral node face densely punculate dorsad, ventrad tending to smooth. Anterior postpetiolar margin broadly convex in lateral view, curving onto dorsal margin; gaster mostly finely punctulate, constriction between abdominal segments III and IV shallow; pygidium with more or less well-developed longitudinal crest; procoxae mostly smooth and shining, with anterior longitudinal band of striae. Body with abundant decumbent pilosity and scattered standing-suberect hairs. Head, mesosoma, node and most of gaster black to dark brown; antenna, mandibles, clypeus, and legs brown, apex of gaster brown. Mesotibial apex with single external seta; protibial and metatibial apex without setae.

Queen
Similar to worker except for head more oval shaped in full-face view, small round depression present medially posterad of eyes; propodeal dorsum more convex in lateral view; petiolar node wider than long in dorsal view, and gaster relatively larger in size.

Type Material
Holotype worker. Mexico, Veracruz, Estación Los Tuxtlas, Sub1, 7.vii.2001, J. Valenzuela, deposited in. – Paratypes. (1) Mexico, Veracruz, Estación Los Tuxtlas, Sub1, 7. vii.2001, J. Valenzuela, 1w IEXA, 1w, 1w (same series as holotype). (2) Same locality but PP3, 7.vii.2001, J. Valenzuela, 1w IEXA, 1w.

Etymology
The species name is derived from that of the Sian Ka’a Reserve in Mexico, one of the localities from which it has been collected.