Acanthostichus longinodis

The type series, the only known specimens, were collected from under a stone.

Identification
Mackay (2004) - This initially appears to be a typical South American Acanthostichus species, but can be distinguished from other South American species by the combination of the elongate petiole (Fig. 4), the small subpetiolar process (Fig. 1) and the incrassate posterior femur (Fig. 3). It can be separated from two Mexican species with elongate petioles, Acanthostichus quirozi and Acanthostichus skwarrae Wheeler as the sides of the petiole are sharply separated from the dorsal surface by an abrupt bend which nearly forms a carina. The elongate petiole would preclude confusion with any other species in the genus.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Paraguay.

Nomenclature

 * . Acanthostichus longinodis Mackay, 2004: 97, figs. 1 – 4, 10 (w.) PARAGUAY.
 * Type-material: holotype worker, 2 paratype workers.
 * Type-locality: holotype Paraguay: Dpto Chaco, Parque Nacional Defensores del Chaco, Cerro Léon, zona pelada, sitio #11, 9-15.viii.1983 (J.A. Kochalka); paratypes with same data.
 * Type-depositories: MNSP (holotype); MCZC, WEMC (paratypes).
 * Status as species: Wild, 2007b: 23.
 * Distribution: Paraguay.

Worker
(n = 3, all measurements in mm): HL (Head Length) 0.76-0.78, HW (Head Width) 0.58-0.60, SL (Scape Length) 0.28-0.30, SW (maximum Scape Width) 0.10-0.11, EL (maximum Eye Length) 0.04-0.05, WL (Weber's Length, anterior edge of pronotal shoulder to posterior edge of metapleurallobe) 1.08-1.14, PL (Petiole Length) 0.35-0.40, PW (Petiole Width) 0.23-0.26, SI (Scape index, SL/HL X 100) 35-40, Cl (Cephalic Index, HW/HL X 100) 76-77, PI (Petiolar Index, PL/PW X 100) 150-153, SL/SW 2.78-2.88.

Mandible without teeth; anterior border of clypeus weakly concave, nearly straight; frontal carinae closely spaced, slightly overhanging anterior margin of clypeus with head in full face view (Fig. 2); sides of head nearly straight, slightly widened anteriorly (Fig. 2), posterior border of head slightly concave; scape short; eye tiny, apparently composed of three ommatidia; malar groove well marked; mesosoma basically rectangular in shape as seen from side and as seen from above, narrowed posteriorly (seen from above), with narrowest part being posterior edge of propodeum; propodeal spiracle slightly below midline (Fig. 1); petiole greatly elongated (Fig. 4), anterior face nearly straight, slightly widened posteriorly; posterior femur incrassate (Fig. 3).

Moderately hairy, with erect hairs on scape, mandible, dorsal surface of head, posterior border of head, ventral surface of head, dorsum of mesosoma, dorsum of petiole, and all surfaces of gaster.

All surfaces smooth and glossy.

Ferrugineous red, appendages and gaster slightly lighter.

Type Material
Type series.-Holotype worker (, Museo Nacional de Historia Natural del Paraguay), 2 paratype workers (, William and Emma Mackay collection;, Museum of Comparative Zoology, Harvard University), PARAGUAY: Dpto. Chaco: Parque Nacional Defensores del Chaco: Cerro Leon: zona pelada: Sitio #11; 9-15-viii-1983, Colr. J. A. Kochalka.

Etymology
From Latin, longus for long and nodus for swelling, describing the elongate petiole.

References based on Global Ant Biodiversity Informatics

 * Borowiec M. L. 2016. Generic revision of the ant subfamily Dorylinae (Hymenoptera, Formicidae). ZooKeys 608: 1–280.
 * Mackay W. P. 2004. A new species of the ant genus Acanthostichus Mayr (Hymenoptera: Formicidae) from Paraguay, and a description of the gyne of A. brevicornis Emery. Proceedings of the Entomological Society of Washington 106: 97-101.
 * Wild, A. L. "A catalogue of the ants of Paraguay (Hymenoptera: Formicidae)." Zootaxa 1622 (2007): 1-55.