Proceratium tio

The holotype was found in rainforest leaf litter.

Identification
A member of the stictum clade and to the goliath group, and differing from its sister species Proceratium goliath, in the worker, by the following combination of characters: propodeal teeth larger, ventral process of the petiole distinct and spiniform instead of at most shortly triangular.

Distribution based on Regional Taxon Lists
Neotropical Region: Guatemala, Mexico.

Nomenclature

 *  tio. Proceratium tio Snelling, R.R. & Cover, 1992: 50, fig. 1 (w.) MEXICO. See also: Baroni Urbani & De Andrade, 2003b: 108.

Worker
Baroni Urbani and de Andrade (2003) - Head slightly longer than broad, with sides gently diverging posteriorly. Vertex convex in full face view. Clypeus broad, convex, protruding anteriorly and surrounding the whole antennal insertions. Anteromedian margin of the clypeus with a notch. Frontal carinae very far from each other, strongly diverging posteriorly and not covering the antennal insertions. Lateral expansions of the frontal carinae broad and slightly raised. Frons concave medially. Genal carinae marked. Head ventrally with a pair of superficially impressed longitudinal sulci delimited externally by the genal carinae. Gular area deeply impressed. Eyes composed by a clear, convex facet, and placed slightly below the mid-line of the head. Scapes not reaching the vertexal border. First funicular joint about 1/5 longer than broad. Funicular joints 2-10 broader than long. Last funicular joint as long as the sum of joints 7-10. Mandibles with 3-4 denticles before the apical tooth. Palp formula 4,3.

Mesosoma convex in side view and slightly longer than the head (mandibles included). Promesonotal and propodeal sutures very weakly impressed. Promesopleural and meso-metapleural sutures impressed on the ventral half only. Basal face of the propodeum declivous posteriorly. Declivous face of the propodeum flat; sides of the declivous face carinate. Each side between the basal and declivous faces of the propodeum separate by a broad, subround, carinate tooth. Propodeal lobes subtruncate and apically convex. Propodeal spiracle tumuliform and placed over mid height in lateral view.

Petiole slightly longer than broad, with the sides diverging on the anterior third and convex posteriorly in dorsal view. Anterior border of the petiole gently concave and strongly carinate. Ventral process of the petiole spiniform. Postpetiole slightly shorter than gastral tergite I (LT4), with a broad tumulus close to the center of the posterior border in side view. Postpetiolar sternite anteromedially with a marked subtriangular projection. Posterior half of the postpetiolar sternite convex. Constriction between postpetiole and gastral segment I impressed. Gastral tergite I strongly convex. Remaining gastral tergites and sternites slightly curved ventrally.

Legs slender. All tibiae with a pectinate spur. Spurs of fore legs with a basal spine. Fore basitarsi slightly longer than the mid ones. Hind basitarsi about 1/5 shorter than hind tibiae. Second tarsomere of mid and hind legs longer than each, third and fourth tarsomeres, and slightly shorter than pretarsus. Pretarsal claws simple. Arolia present but small.

Sculpture. Head, mesosoma, petiole and postpetiole irregularly foveolate-punctate. Caster smooth and with sparse, minute piligerous punctures. Legs with dense piligerous punctures.

Body covered by hairs of three main types: (1) short, dense, subdecumbent on the whole body, suberect and sparse on the funicular joints; (2) long, suberect or subdecumbent, relatively dense on the whole body, absent on the scapes and funicular joints; (3) shorter than hair type (1), dense and decumbent on the funicular joints only. In addition, the funicular joints bear thick, appressed, short, sparse hairs and the scapes sparse, subdecumbent hairs slightly shorter than hair type (2).

Colour brownish-red, antennae and legs lighter.

Measurements in mm and Indices (specimen from CPCC): TL 5.30; HL 1.25; HW 1.17; EL 0.08; SL 0.87; WL 1.52; PeL 0.60; PeW 0.54; HFeL 1.16; HTiL 0.94; HBaL 0.74; LS4 0.14; LT4 0.92; CI 93.6; SI 70.2; IGR 0.15.

Type Material
Baroni Urbani and de Andrade (2003) - Type locality: Veracruz, Mexico. Type material: a worker labelled: "Mex: Vera Cruz, 6 mi NE Catemaco, VII.7.1976, elev. 1500', A. Newton, Berl. Rainforest leaf litter, Holotype", in, examined.

References based on Global Ant Biodiversity Informatics

 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Longino J. T. L., and M. G. Branstetter. 2018. The truncated bell: an enigmatic but pervasive elevational diversity pattern in Middle American ants. Ecography 41: 1-12.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133