Odontomachus cornutus

The range of ''0. cornutus'', as presently known, is restricted to the two sites on the Pacific slope of the Colombian and Ecuadorian Andes.

Identification
Key to Odontomachus of the New World

Distribution based on Regional Taxon Lists
Neotropical Region: Ecuador.

Biology
All specimens were taken from Finca los Guaduales, the farm of Jim West, Meredith Foyle and Jack Sachs, some IO km southwest of San Jose de! Palmar (about 5 km by road to La Badea, then footpath for about 3 hours), Departamento de! Choco, Colombia on 1-4 June 1978 by C. Kugler. Four workers and a dealate queen were collected as strays from the lower boundary of the property on the Rio Torito, 610 m. Three more workers and 2 males were found in a nest or nest fragment in soft deep soil under leaf litter on a ridge above the farm buildings, 850 m. Few individuals and no larvae were seen in this "nest ," even after digging down to 30 cm. In both places the vegetation is montane forest, apparently primary. The area has been colonized only in the last 10 years, and this finca has escaped extensive cutting. The present owners hope to preserve the major part of their land in its natural state, and they welcome visiting scientists. Annual rainfall in 1977, as measured by a home rain gauge, was 4.8 m. Driest months are January, February, July and August (4.5 cm to 16.6 cm per month).

Nomenclature

 *  cornutus. Odontomachus cornutus Stitz, 1933: 67, fig. 1 (w.) ECUADOR. Kugler, C. 1980: 225 (q.m.). See also: Brown, 1976a: 144.

Description
metric characters, those of smallest worker followed by those of largest: TL 13.68, 18.71 ; HL 3.40, 4.56; HW (across vertex) 2.00, 3.10; HW (across ocular prominences) 2.90, 3.84; ML 2.15, 2.75; scape L 3.6, 4.36; eye L 0.36, 0.44; WL 4.08, 5.36; hind femur L 4.10, 5.12; hind tibia L 3.40, 4.24; petiole L 0.85, 1.20; CI (using HW across vertex) 59, 68; MI 63, 59; SI 180, 141. Composite description of worker: Mandibles long, more robust in major workers (maximum mandible W excluding teeth/ML = 28%) than in minors (23%). Callows (Fig. I ) with acute apical and intercalary teeth; very long, truncate subapical tooth; and 14-17 teeth along the entire length of the ventral masticatory border, gradually diminishing in size basad, and changing from triangular to slender and curved. In older ants all teeth wear to shorter and more rounded. Palpal formula 4, 4. Head (Fig. I ) with ocular prominences drawn out as stout oblique teeth; median furrow strongly impressed and confluent with antennal fossae ; occipital carina not strongly produced. Eyes small (EL/HL = 10-11%). Scapes extend well beyond oc­cipital corners (by 20% of SL in smallest worker; by 15% in largest). Trunk profile usually with metanotum declining caudad to a variable de­gree so that there is a distinct step up to the propodeum, but in some specimens (Fig. 2) metanotum and propodeum are continuous and nearly flat. Metasternum without metasternal processes. Mesepisterna without an­ teroventral lobes when seen from above. Apical tibial spurs 1, 2, 2. Orifice of propodeal spiracle subcrescentic. Petiolar node in profile (Fig. 2) with a sloping, sinuous anterior face; posterior face weakly convex below, straight along vertical apical spine. Anterior penduncle with a prominent, sharp, upturned lip. Node as seen from the front not swollen; weakly convex sides converge to base of spine, then through a broadly concave arc become strongly tapered and flat to the acute apex of the compressed spine. Anterior edge of spine more or less carinate, and in some specimens the sharp edge extends about halfway down the node. Subpetiolar process subtriangular, with convex anterior edge, concave posterior edge, and bluntly rounded apex. Gaster with a narrow, triangular stridulatory file on second acrotergite. Sculpture: Mandibles and head smooth and shining, except for weak lon­gitudinal striation between frontal carinae, and coarse, fan-like striation in antenna! fossae. Weak longitudinal striation also on ventral aspect of an­ terior comers of head. Piligerous punctures are scattered throughout. Prono­tum with fine, whorled striation above, bracketed by bands of transverse striae fore and aft, the latter flaring ventrad to cover humeri. Mesonotum, metanotum and propodeum (including declivous face) transversely striate; slightly coarser on the propodeum. Anteriormost striae of propodeum longitudinal in some specimens. Sides of mesopleura largely smooth, but with effaced, largely vertical striation on each end; ventral aspect covered trans­versely with same weak sculpture. Legs, petiolar node and gaster smooth and shining, with scattered piligerous punctures. Gaster also with very fine, dilute pitting best seen at 50 x. Light yellow to golden pubescence of about 0.05-0.2 mm present on all parts of body except nude posterior face of petiole; predominant and dense on tibiae, tarsi, antennae and propodeum; dilute, appressed and difficult to see on gaster and upper surfaces of mandibles. Somewhat longer hairs (up to 0.3 mm) on head, trunk, petiole, coxae and femora. Longest (0.3-0.7 mm), more erect, and golden to light brown pilosity only on ventral surfaces of mandibles, near midline of head (dorsum, 28-36 hairs; venter, 20-22; labium, 2), disc of pronotum (14-16), ventral surfaces of coxae, flexor surfaces of femora (3-8), and throughout gaster except for anterior face of first tergum. Body uniformly ferruginous brown with darker frontal carinae and clyp­eus, and largely black mandibles. Violaceous reflections seen on all parts (under strong lighting); more bluish over more darkly colored areas. This description departs from that of Stitz (see also Brown, 1976: 144) only in minor ways: width of vertex and shape of mandibles (as shown by his figure), extent of preapical dentition, striation and pilosity on pronotal disc, and a slightly different interpretation of color. Notable only is his statement that the pronotum is transversely striate above; all of mine are predominantly whorled. TL 19.16; HL 4.79; HW (across vertex) 3.23; HW (across ocular prominences) 4.05; ML 2.92; scape L 4.60; eye L 0.65; WL 5.92; hind femur L 5.20; hind tibia L 4.40; petiole L 1.30; CI 67; MI 61; SI 142. Single specimen dealate; differs from workers in the normal ways, and in the following: Striation on pronotum entirely transverse; that on meso- and metanota longitudinal. Petiole from the side with anterior face concave up to base of relatively broader spine, at which point there is a small step down in the outline. Apical spine curved more caudad, giving the posterior face a more concave outline (flattened midlength). Anterior peduncle without sharp upturned lip. TL 10.24, 10.42; HL 1.27, 1.30; HW (across eyes) 1.80, 1.84; ML (chord) 0.25, 0.22; eye L 0.85, 0.88; maximum diameter of median ocellus 0.20, 0.19; WL 4.00, 4.14; petiole L 0.95, 0.98; CI 141, 142; MI 173, 192. Head short, without a neck. Anterior clypeal margin very weakly convex. Mandibles short, compressed apically into blunt, smoothly rounded paddles; outer surfaces with a few short setae, none more prominent or stiff than the others. Free edge of labrum strongly emarginate, lateral corners acute. Pal­pal formula 6, 4. Mesoscutum lacks notauli. Mesonotum and metanotum with weak to prominent median carina. Propodeal spiracles subcriscentic, placed on  prominent  tubercles;  anterior  peduncle  with  sharp  upturned lip. Wings typical for Ponerini. Petiolar node a short,  acute  to  subacute cone. First gastric segment not constricted behind. Spine of pygidium seen from the side straight or weakly downcurved, parallel-sided,  apex  blunt; from above, tapered and acute. Parameres widely  rounded  apically. Sculpture on head from smooth or very weakly alutaceous around eyes to weakly roughened elsewhere. Scattered piligerous punctures occur throughout. Trunk rather strongly sculptured. Mesonotum mostly longitu­ dinally striate; pronotum, pleura and propodeum striate to rugose-striate; orientation of striae varies slightly between the 2 specimens. Wide, im­ pressed bands with bridging striae or costae mark some sutures of sides. Petiole grades from smooth above to striate on sides. Gaster smooth to alutaceous, very shiny, and with scattered piligerous and nonpiligerous punctures throughout. Pubescence much as described for worker, but more conspicuous on gas­ ter; none on upper surfaces of mandibles. Pattern of pilosity also much the same, but shorter (up to 0.5 mm); and emergent hairs not so obvious on head, absent on mandibles and arrayed  on pronotum  along promesonotal suture. Color shiny black except for dark brown face, legs beyond the femora, and hind segments of gaster; brown clypeus, scape and pedicel; yellow­ brown terminalia and trochanters. Antennae not shining due to dense pu­bescence. Bluish reflections most clearly seen on smooth areas.
 * Worker
 * QUEEN:
 * MALES (2 specimens):