Trachymyrmex pakawa Sanchez-Pena , Chacon-Cardosa , Canales-Del Castillo & Resendez-Perez

Sanchez-Pena, Sergio R., Chacon-Cardosa, Manuela Citlali, Canales-del-Castillo, Ricardo, Ward, Lauren & Resendez-Perez, Diana, 2017, A new species of Trachymyrmex (Hymenoptera, Formicidae) fungus-growing ant from the Sierra Madre Oriental of northeastern Mexico, ZooKeys 706, pp. 73-94 : 78-80

Trachymyrmex pakawa Sanchez-Pena, Chacon-Cardosa, Canales-Del Castillo & Resendez-Perez sp. n. (Figures 2, 3, 4)

Type material investigated.

Holotype worker: MEXICO, Saltillo, Coahuila; Lomas de Lourdes, 25.365181°N, 100.983217°W, 15.viii.2012, dry oak forest, ex ground (S. R. Sanchez-Peña). Collection code: UAN446. Specimen code: USNMENT01125073 (USNM).

Paratypes.

Additional specimens (workers) with the same collection information as the holotype deposited at ASU-SIBR, CASC, UAAAN, UNAM and USNM.

Additional material.

Additional material: MEXICO, one worker. Cerro de las Mitras, Monterrey, Nuevo León, 25.704834°N, - 100.397027°W, 24.viii.2008. Foragers on montane chaparral (S. R. Sanchez-Peña) (UCDC, Philip Ward).

Diagnosis (worker).

Similar to Trachymyrmex smithi but antennal scapes clearly longer, resulting in Scape Index values of 93-109 (Figure 2); head not as clearly cordate, nor broader than long; color dark reddish brown or rarely light ferruginous red. See Measurements in Table 2.

Description.

Head trapezoidal, weakly cordate (Figure 2); HW= 1.13, HL= 1.1 (mm) (holotype), nearly square or slightly rectangular, very slightly broader than long; head widest at midpoint between the eye and the posterior corner, and tapering anteriorly. Posterior margin of head is only moderately concave, slightly notched.

Vertex of head and gaster moderately tuberculate, more markedly spinulose than T. smithi ; tubercles thin and resembling spines, base of tubercles not confluent as in T. smithi . Tubercles on preoccipital lobes almost as long as preoccipital spines. Supraocular projections absent. Discal area of mandibles finely striated.

In full-face view, the frontal lobes are small, broadly triangular, usually asymmetrical, with anterior margin longer than posterior (Figure 2).

The margin of the frontal lobes is sub-triangular, smooth, and not crenulated; the base of the frontal lobes lacks projections. Anterior and posterior margin of frontal lobes straight.

Base of antennal scapes lacking lobe. Anterior surface of antennal scapes smooth or weakly microtuberculate. Antennal scapes long, surpassing the posterior corner of head by more than twice their maximum diameter.

Frontal and preocular carina ending separately. In full-face view, frontal carina extends almost to posterior corners, but weakening before reaching vertex. Preocular carina well developed, crossing nearly half distance between eye and frontal carina, curving mesad towards, but not reaching, the frontal carina; frontal carina faintly reaching posterior cephalic margin, forming weakly developed, closed antennal depressions ( “scrobes”) without apical tubercles.

Tubercles of gaster and mesosoma small, tubercular setae are weakly to strongly recurved; tubercles on sides of mesosoma minuscule and sparse (Figure 2). Pilosity of gaster and femora consists of hairs only, lacking fine pubescence. Texture of body surface rough, sandpaper-like. In T. pakawa the color is dull reddish to (almost always) dark reddish to dark brown, but unlike T. smithi , no blackish specimens have been observed. Dorsal projections of mesosoma are multituberculate swellings, tooth- or spine-like (Figure 2). Two median pronotal projections are present, appearing as ridges or multituberculate swellings. The inferior pronotal corner has a rounded, blunt, weakly developed, projecting tooth. Anterior median promesonotal tubercles short, vertical, tooth-like in frontal or posterior view. The anterior mesonotal projections are microscopically multituberculate or multidentate swellings, especially in Saltillo collections; they are nearly as long as pronotal lateral projections in La Estanzuela (Monterrey) but notably longer than pronotal lateral ones in material from Saltillo. Posterior mesonotal projections present, shaped as a ridge or multituberculate tooth or tumulus. Pilosity of mesopleura consisting of approxi mately twelve short, pale (not reddish) thin curved hairs, about half as long as hairs on mesosomal projections. Projections on inferior and superior margin of mesopleura absent.

The propodeal teeth are strongly divergent, spine-like, and longer than distance separating their bases; the teeth are longer than any promesonotal projections, and longer than projections of basal face. The petiolar node has one pair of teeth in specimens from La Estanzuela, and two (rather clearly) defined pairs of teeth in specimens from Saltillo. Petiolar node from above is as long as broad. Postpetiole from above is distinctly wider than long; the posterior border of postpetiole is notably excised.

Etymology.

From the name of an ancient, vanished Native American tribe that used to live in the same general area of arid northeastern Mexico, where Trachymyrmex pakawa is known to occur.

Distribution.

From warm-temperate forest and scrubland habitats at the northern Sierra Madre Oriental range in the Mexican states of Coahuila and Nuevo León: more specifically, in the northern Gran Sierra Plegada range and mountains between the cities of Monterrey and Saltillo. This species has also been collected in the mountains in the municipality of Iturbide, Nuevo Leon, near coordinates 24.721111, -99.896389, about 100 km to the south of Monterrey.