Leptogenys elongata

Identification
Key to Leptogenys of the New World

Lattke (2011) - Head sub-quadrate to sub-rectangular in full-face view, wider anterad than posterad; anterior clypeal margin tapers evenly to median process, lateral lobes weakly developed; mesosternum sharply separated from mesopleuron by carina that expands anterad into modest lobe; surface of head and mesosoma dull, with coarse punctuations; color deep yellow-red to black.

A member of the elongata species group.

Distribution
This taxon was described from the United States. It is known from eastern Mexico – southcentral USA.

Biology
Lattke (2011) - Leptogenys elongata may be found in caves in Texas (Cokendolpher et al. 2009), though in the same paper the authors record an apparently undescribed Leptogenys found in one Texas cave. It appears to be a pusilla group member and does not have traits that could be deemed troglobitic save the reduced eyes, which is frequent in said group.

Nomenclature

 *  elongata. Ponera elongata Buckley, 1866: 172 (w.) U.S.A. Wheeler, W.M. 1900b: 7, 16 (q.m.l.); Wheeler, W.M. 1904c: 258 (w.q.m.); Wheeler, G.C. & Wheeler, J. 1952c: 641 (l.); Petralia & Vinson, 1980: 378 (l.). Combination in Leptogenys: Emery, 1895c: 268; Wheeler, W.M. 1900b: 2. Senior synonym of septentrionalis, texana: Wheeler, W.M. 1902f: 25; Wheeler, W.M. 1904c: 257; of mexicana: Lattke, 2011: 157.
 * mexicana. Lobopelta mexicana Mayr, 1870b: 966 (w.) MEXICO. Combination in Leptogenys: Forel, 1899c: 18. Junior synonym of elongata: Lattke, 2011: 157.
 * septentrionalis. Lobopelta septentrionalis Mayr, 1886d: 438 (w.) U.S.A. Combination in Leptogenys: Emery, 1895c: 268. Junior synonym of elongata: Wheeler, W.M. 1902f: 25.
 * texana. Ponera texana Buckley, 1866: 170 (w.) U.S.A. Combination in Leptogenys: Emery, 1895c: 338. Junior synonym of elongata: Wheeler, W.M. 1902f: 25; Wheeler, W.M. 1904c: 258.

Lattke (2011) - It was not possible to locate the types of Leptogenys described by Buckley nor ascertain if they exist. S.B. Buckley described many species of plants and animals during his lifetime and left a legacy of poor descriptions and apparent absence of type specimens which have since vexed myrmecologists and other taxonomists (Mayr 1886b; Wheeler 1902). At least some ant types existed during the late 1870’s in the collections of the Academy of Natural Sciences of Philadelphia, but regrettably vanished later on (Snelling 1995). The descriptions of both L. elongata and L. texana seemingly agree with the present concept of L. elongata, but the possibility exists they could be something else. If more investigations into the whereabouts of the Buckley types can soundly conclude they do not exist or met a unfortunate end, neotype designation should be considered. As aptly put by Snelling (1995), “The identity of Buckley’s species must, of necessity, rely on speculation”.

The examination of both syntypes of L. septentrionalis revealed nothing that could render it different from L. elongata, thus supporting Wheeler’s synonymy. The description of this species cites “Districte Columbia” as the type locality, an obvious error as the District of Columbia lies far beyond the range of L. elongata. Mayr (1870) described L. mexicana from a specimen apparently collected by D. Bilimek, though Emery’s last name figures alongside that of Bilimek perhaps hinting the Bilimek collected ant came to him by way of Emery. Emery did not venture far from Italy, but Bilimek did collect in Mexico. The type of L. mexicana was the only type specimen of the species to be found, at least in the major European and US museums, implying the species was described from a single specimen. Mayr gave importance to the heavily punctate sculpturing which he asserted to distinguish the new species from all other congeners. Such sculpturing is now known to exist in several other Leptogenys, including the form L. elongata. Even though Mexican specimens tend to have heavier punctation than those from Texas, heavily punctate specimens can also be found north of the Río Grande whilst sparsely punctate specimens can also be found south of said river. The northern populations are lighter colored than the southern populations, but the two shades are not contrastingly different when compared throughout the distribution range. Specimens from Texas and Louisiana are yellow-red to brown-red, with Mexican specimens ranging from black to very dark brown. On average the shape of the petiole seen dorsally is relatively slender in Texas material whilst it is commonly more subquadrate in Mexican specimens, but Mexican specimens with slender petioles exist, as well as specimens from Texas or Louisiana with a more robust petiole. The shape of the parameres and aedeagus in Mexican males is similar to those of males from northern localities, further undermining the species status of L. mexicana.

L. elongata can be easily confused with Leptogenys manni, the putative sister species, originally described as a subspecies of L. elongata by Wheeler (1923) and elevated to species rank by Trager & Johnson (1988). The diagnosis should suffice to separate the two, but additional characters are given in the discussion for L. manni. Judging from the amount of specimens deposited in various collections, Mesa de Chipinque near Monterrey, and central Texas constitute reliable localities for collecting this species. Trager & Johnson (1988) point out the months of March to May as optimal for finding these ants beneath rocks and logs. Disturbed habitats, such as highway rights of way, are also favored by these ants, perhaps due to the availability of the tramp isopod Armadillidium sp. Wheeler (1900, 1904) studied the biology of this species and additional information is available in Trager & Johnson (1988). This species is cited (Dejean et al. 1995; Dejean & Olmsted 1997) as nesting in rotting ramets of the bromeliad Aechmea bracteata in the Reserva Sian Ka’an in Quintana Roo, Mexico, but an examination of voucher specimens in the revealed that it is actually another elongata group species, Leptogenys sianka, described in this revision. Quiroz-Robledo & Valenzuela-González (2007) record the species from the state of Morelos inhabiting tropical deciduous forest and thorn forest between the altitudes of 990 – 1190 m.

Worker
Lattke (2011) - Metrics (n = 8): HL 1.35-1.55; HW 1.01-1.11; ML 0.81-0.88; EL 0.24-0.34; SL 1.42-1.69; PW 0.84-0.91; WL 2.22-2.56; PH 0.88-0.91; PL 0.71-0.84; DPW 0.51-0.57 mm. CI 0.71-0.80; MI 0.75-0.84; OI 0.23-0.32; SI 1.27-1.61; LPI 1.13-1.23; DPI 0.65-0.81.

Head sub-quadrate to sub-rectangular in full-face view, wider anterad than posterad; lateral margin anterad of eye straight, and posterad of eye broadly convex; posterior cephalic margin straight to broadly convex; median clypeal process tapers to rounded, lamellate apex, apex with two long hairs, no setae; lateral process narrow, its outline smoothly joining with outline of median process. Eye broadly convex, occupies under one-third of lateral cephalic margin, situated at mid-length, slightly dorsad. Cephalic dorsum densely punctate, distance between each depression less than their respective diameter, longitudinal to oblique striae present between eye and antennal insertion; longitudinal sulcus stretches from between frontal carinae to mid-eye height. Scape mostly smooth and shining with fine punctulae and abundant decumbent pilosity and occasional hairs, scape extends beyond posterior cephalic margin by one-fourth its length; third funicular segment 3 x longer than apical width, about two-thirds length of second segment; each funicular segment wider apicad than basad. Mandible triangular, shuts tight against clypeus, with fine weak longitudinal striae and sparse punctae; chewing border edentate, basal angle blunt; PF: 4,3.

Mesosoma with broad and deep metanotal groove in lateral view that separates promesonotal margin and dorsal propodeal margin, both broadly convex; lateral pronotal sculpture mostly longitudinally rugulose, obliquely transverse on mesometapleural and lateral propodeal faces. Mesometapleural suture well impressed; metapleural-propodeal suture not impressed or appearing as brief narrow ledge just anterad of propodeal spiracle; propodeal spiracle elongate, slit-shaped, oriented posteriorly; dorsum of pronotum with arching rugulae; rugulae on propodeal dorsum mostly transverse with striae close to petiolar insertion; declivitous face transversely striate, rounding to lateral propodeal face, not separated by sharp ridge; propodeum with low triangular lobe at spiracle height; prosternum transversely striate to rugulose. Mesosternum sharply separated from mesopleuron by carina that expands anterad into modest lobe, lobe with crest that extends mesad on mesosternum delimiting narrow transverse area on anterior mesosternal margin; mesonotum slightly elongate in dorsal view, anterior margin convex; metanotal groove straight to convex, smooth.

Petiole sub-quadrate to elongate in lateral view, higher posterad than anterad; anterior margin more than one-half height of posterior margin, anterior margin straight, dorsal margin convex, posterior margin weakly convex to straight. Subpetiolar process rectangular to lobe like in lateral view with concave posterior margin. Node subquadrate to elongate in dorsal view; anterior margin convex, more than half width of posterior face; posterior face straight; sides straight to very broadly convex. Posterior face rounds to lateral face, sometimes separated ventrad by low ridge; lateral node face with longitudinal striae dorsad, ventrad tending to smooth with weak undulations and rugosities; dorsum with transverse to oblique low striae. Anterior postpetiolar margin broadly convex in lateral view, curving onto dorsal margin; gaster smooth and shining, constriction between abdominal segments III and IV well marked; procoxae with sparse low rugulosities, mostly smooth. Body with abundant decumbent pilosity and scattered standing-suberect hairs. Head, mesosoma node and most of gaster black to ferruginous brown or ferruginous; antenna, mandibles, legs and apex of gaster brown to ferruginous. Meso and metatibial apex each with single external seta.

Queen
Lattke (2011) - Metrics (n = 2): HL 1.38-1.42; HW 1.08-1.15; ML 0.81-0.88; EL 0.27-0.30; SL 1.45-1.55; PW 0.88-0.91; WL 2.26-2.29; PH 0.78-0.81; PL 0.67-0.71; DPW 0.67-0.67 mm. CI 0.76-0.83; MI 0.75-0.76; OI 0.25-0.26; SI 1.34-1.35; LPI 1.10-1.20; DPI 0.95-1.00. Similar to worker except for: head more oval shaped in full-face view, propodeal dorsum more convex in lateral view; petiolar node wider than long in dorsal view, and gaster relatively larger in size.

Male
Lattke (2011) - Not measured. Head mostly smooth and shining with some transverse striae anterad of antennal fossae. Pronotum mostly punctate, punctae denser medially than laterally; anterior mesonotum separated by gap from posterior pronotum. In dorsal view scutum with shallow impressed medial line extending anterad from anterior base of scutellum, bifurcating and joining notauli between tegulae; parapsidal line impressed from anterior base of axilla until almost touching notaulus; impressed lines with same color as surrounding cuticle. Mesonotum and mesopleuron mostly smooth and shining with punctulae; metapleuron and propodeum mostly with low rugulosities.

Type Material
Lattke (2011):

Ponera elongata. Holotype worker: United States, Texas [not examined].

Ponera texana. Holotype worker: United States, Texas [not examined].

Lobopelta septentrionalis. Syntype workers: United States, Districte Columbia (Pergande) [examined].

Lobopelta mexicana. Holotype worker: Mexico (Bilimek) (NHMW) [examined].

Additional References

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