Proceratium micrommatum

In Costa Rica this species is known from lowland wet forest. The species is encountered as isolated workers in sifted leaf litter samples from the forest floor. (Longino, Ants of Costa Rica).

Identification
A member of the micrommatum clade. Similar to Proceratium panamense and Proceratium poinari, but differing from panamense, in the worker and gyne, by the smaller size (worker TL < 3.60 mm instead of 3.80 mm, gyne TL < 3.60 mm instead of 4.57 mm) and by the SI ≥ 61.7 instead of ≤ 60.8; and from poinari by the worker and gyne IGR ≤ 0.16 instead of ≥ 0.23. (Baroni Urbani and de Andrade 2003)

Key to Nearctic and Neotropical Proceratium Species

Distribution based on Regional Taxon Lists
Neotropical Region: Colombia, Costa Rica, Guatemala, Honduras, Mexico, Panama, Venezuela.

Nomenclature

 *  micrommatum. Sysphingta micrommata Roger, 1863a: 176 (w.) SOUTH AMERICA. Combination in Proceratium: Dalla Torre, 1893: 18; Forel, 1895b: 111. Senior synonym of cavernicola: Borgmeier, 1957: 118. See also: Brown, 1958g: 333; Baroni Urbani & De Andrade, 2003b: 172.
 * cavernicola. Sysphincta cavernicola Borgmeier, 1937b: 221, figs. 1-4 (q.) PANAMA. Weber, 1940b: 79 (w.). Junior synonym of micrommatum: Borgmeier, 1957: 118.

Baroni Urbani and de Andrade (2003) - Proceratium micrommatum is the most widespread species of its clade. Nonetheless the distribution given in this paper is much narrower than the one resulting from the previous literature. In fact four new species described in this paper have been previously identified as micrommatum.

Ward (1988) attributed a male from south Texas (Hidalgo County) to micrommatum or to the micrommatum complex. He added that the male is relatively small (HW 0.66 mm), with strongly recurved gaster (IGR 0.32) and mid tibia without spur. We did not see the specimen in question but we agree that it should belong to the micrommatum clade. It is very likely, however, that this male should be referred to Proceratium mexicanum (q. v.).

Borgmeier (1957) proposed the synonymy of his Sysphincta cavernicola Borgmeier with Proceratium micrommatum (Roger). We examined the holotype of both species and we confirm the synonymy.

Brown (1974) doubted the specific validity of convexiceps Borgmeier. We consider Proceratium convexiceps as a valid species. The reasons for our conclusion are given under the discussion of convexiceps.

The identification keys by Brown (1980) and by Ward (1989) list the presence of micrommnatum also in Ecuador. The only specimens from Ecuador belonging to the micrommatum clade that we examined represent a new species described in this paper as Proceratium ecuadoriense.

Worker
Baroni Urbani and de Andrade (2003) - Head longer than broad, slightly narrower anteriorly than posteriorly. Vertex in full face view straight. Clypeus very reduced, triangular or round, between the and slightly longer than the antennal sockets. Antenna1 sockets with broad torulus. Frontal carinae close each other, not covering the antenna1 insertions. Frontal area behind the frontal carinae weakly convex. Lateral expansions of the frontal carinae relatively narrow, raised, diverging or subparallel. Genal carinae poorly marked. A superficial sulcus between the genal carinae and the gular area. Eyes present, composed by a clearly convex facet placed below the midline of the head. Ocelli absent. Scapes thicker in the distal half and short of the vertexal margin. First funicular joint 1/3 longer than broad. Funicular joints 2-10 broader than long. Last funicular joint as long as the sum of joints 6-10. Masticatory margin of the mandibles with 3 denticles before the apical tooth. Palp formula 3,2.

Mesosoma slightly convex in side view. Promesonotal and propodeal sutures absent. Promesopleural and mesometapleural sutures impressed on the ventral half only. Basal face of the propodeum gently declivous or weakly convex, with a superficial trace of a transversal sulcus close to the declivous face; the sulcus sometimes posteriorly carinate. Declivous face of the propodeum with the sides superficially marginate, the margin more marked posteriorly. Propodeal lobes subround and with variably crenulate margin. Propodeal spiracles small and tumuliform.

Petiole as broad as long, in dorsal view with the sides subparallel in the anterior fourth or fifth and convex posteriorly. Anterior border of the petiole straight or concave, variably carinate and angulate on each side. Ventral process of the petiole subtriangular and small. Postpetiole less than 1/2 of the length of the gastral tergite I (LT4), in dorsal view anterolaterally gently angulate and with the sides weakly convex. Postpetiolar sternite anteromedially with a superficially marked subtriangular projection. Posterior half of the postpetiolar sternite straight or slightly convex. Constriction between postpetiole and gastral segment I deeply impressed. Gastral tergite I slightly angulate on the curvature, less round than panamense. Gastral sternite I very short medially. Sides of gastral sternite I protruding anteriorly, obtuse and carinale. Remaining gastral tergites and sternites curved ventrally. Sting developed.

Legs moderately elongate. Mid tibiae without spur. Spurs of fore legs without basal spine. Fore basitarsi longer than the mid ones. Hind basitarsi about 1/5 shorter than hind tibiae. Second tarsomere of mid and hind legs longer than third and fourth tarsomeres, and slightly shorter than pretarsus. Pretarsal claws simple. Arolia very small.

Sculpture. As in panamense but the petiole and postpetiole with sparser foveae-like depressions.

Pilosity. As in panamense but with hairs of type (2) shorter and less recurved.

Colour light brown-ferrugineous with lighter antennae and legs.

Measurements in mm and Indices: TL 2.64-3.53; HL 0.62-0.81; HW 0.53-0.72; EL 0.04-0.05; SL 0.40-0.50; WL 0.72-0.95; PeL 0.26-0.35; PeW 0.23-0.35; HFeL 0.45-0.61; HTiL 0.37-0.50; HBaL 0.28-0.35; LS4 0.10-0.14; LT4 0.65-0.90; CI 85.5-89.7; SI 6 1.7-64.5; IGR 0.14-0.16.

Queen
Baroni Urbani and de Andrade (2003) - It differs from the worker in the following details: eyes large, shorter than 1/3 of the head length and with ocular pilosity. Ocelli well developed. Mesosoma robust and convex in profile. Parapsidal furrows weakly impressed. Scutellum with the sides converging posteriorly and with the posterior border round. Metanotum without tooth or spine-like projection. Basal face of the propodeum very short, laterally weakly angulate, medially incised and as flat as the declivous face.

Fore wings of our type 5, hind wings of our type 3 as defined in the description of the genus.

Sculpture. Mesonotum less granulate and more smooth.

Measurements in mm and Indices: TL 3.25-3.55; HL 0.66-0.71; HW 0.58-0.63; EL 0.18-0.20; SL 0.42-0.45; WL 0.91- 1.00; HFeL 0.53-0.56; HTiL 0.42-0.45; HBaL 0.32-0.35; LS4 0.1 3-0.16; LT4 0.89-0.98; CI 86.6-89.3; SI 63.3-64.5; IGR 0.15-0.16.

Type Material
Baroni Urbani and de Andrade (2003) - Type locality: South America. Type material: holotype worker labelled: "Siid-America; Proceratium micrommatum (Rog) Em; TYPE; 1895; Sysphincta Roger; micrommata Roger; Zool. Mus. Berlin", in ZMBC, examined.

Sysphincta cavernicola Type locality: Panama. Type Material: Holotype gyne labeled: “Chilibrillo Caves, Panama, L. H. Dunn, 1931, C-99; Typus; Holotypus.