Proceratium diplopyx

Specimens have been collected from rainforest habitats.

Identification
Brown (1980) - This altogether extraordinary ant is distinguished at once from its congeners by the strongly produced and downcurved "false apex" of the second gastric segment, as well as by the form of the propodeum, and several minor characters of sculpture. Relatively large size, large but single facetted eyes, elongate petiole, coarse sculpture and developed propodeal teeth.

Baroni Urbani and de Andrade (2003) - Differing from all the species of the stictum clade by the gastral tergite I greatly hypertrophied posteriorly.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 * . Proceratium diplopyx Brown, 1980b: 337, figs. 1, 2 (w.) MADAGASCAR.
 * Type-material: holotype worker, 1 paratype worker.
 * Type-locality: holotype Madagascar: Prov. Tamatave, Baie d’Antongil, Iaraka, 1000 m., 26.xi.1969 (J.-M. Betsch); paratype with same data.
 * Type-depositories: MNHN (holotype); MCZC (paratype).
 * Status as species: Bolton, 1995b: 366; Baroni Urbani & De Andrade, 2003b: 71 (redescription).
 * Distribution: Madagascar.

Baroni Urbani and de Andrade (2003) - P. diplopyx is the most distinctive species of the stictum clade and of the whole genus for the shape of the gastral tergite I. Brown (1980) suggested to consider diplopyx as representing a species group of its own. In spite of the bizarre gastral morphology, however, Brown (1. c.) stressed the affinities of diplopyx with his sticturn group. In our analysis, diplopyx appears as a member of the stictum clade with which it shares synapomorphically the basal spine on the protibial spur. If, on one hand, considering the diplopyx grotesque gastral shape worthy of a separate group could be considered a matter of taste, on the other hand, its resolved phylogenetic position within the stictum clade represents an obstacle to this course of action.

Worker
Baroni Urbani and de Andrade (2003) - Head longer than broad with sides gently converging posteriorly. Vertex weakly convex in full face view and flat in dorsal view. Clypeus broad, convex, protruding anteriorly and surrounding the whole antennal insertions. Anteromedian margin of the clypeus with a very superficial notch. Frontal carinae apart each other, subparallel and not covering the antennal insertions. Lateral expansions of the frontal carinae narrow and low. Frons medially concave. Genal carina marked. Gular area gently impressed. Eyes present, with a single convex facet placed below the mid line of the head. First funicular joint longer than broad. Funicular joints 2-10 slightly longer than broad. Scapes reaching the vertexal margin and gently thickening apically. Masticatory margin of the mandibles with 3 denticles before the pointed apical tooth. Palp formula 4,3.

Mesosoma slightly longer than the head (mandibles included). Promesonotal and propodeal sutures absent. Promesopleural and mesometapleural sutures more impressed ventrally. Basal face of the propodeurn convex. Each side of the propodeurn between basal and declivous face with a pointed tooth. Propodeal lobes with a small, triangular dorsal tooth. Propodeal spiracle tumuliform.

Petiole 1/5 longer than broad. Petiole in dorsal view with the sides diverging on the anterior third and convex on the two posterior thirds. Anterior border of the petiole concave and carinate, the carina denticulate on each side. Ventral process of the petiole small and obtuse. Postpetiole about half of the length of the gastral tergite 1. Postpetiolar dorsum with a broad tumulus on the middle of the posterior half. Postpetiolar sternite anteromedially with a marked subtriangular projection followed by a short longitudinal superficial carina prolonging backwards. Posterior half of the postpetiolar sternite convex. Constriction between postpetiole and gaster impressed. Gastral tergite I deeply hypertrophied posteriorly. Remaining gastral tergites and sternites curved ventrally.

Legs slender, elongate. All tibiae with a pectinate spur. Spurs of fore legs with a basal spine. Fore basitarsi as long as the mid ones. Hind basitarsi about 0.8 of the length of the hind tibiae. Second tarsomere of inid and hind legs longer than third and fourth tarsoineres and about as long as the pretarsus. Pretarsal claws simple. Pretarsal arolium small.

Sculpture. Head irregularly reticulorugose; in addition to this sculpture, the frons, the vertex and the sides of the head very irregularly foveolate-granulate. Mesosoma, petiole and postpetioie very irregularly foveolate-granulate, the granulation raised as peaks. First gastral tergite smooth and with sparse granulation. Legs and scapes with dense punctures.

Body covered by hairs of three main types: (1) short, dense, subdecumbent on the whole body, erect and sparse on the funicular joints; (2) long, suberect or subdecumbent, sparse on the whole body but absent on the scapes and funicular joints; (3) shorter than the 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 hairs shorter than hair type (2).

Colour reddish-brown.

Measurements in mm and Indices: TL 5.86; HL 1.44; HW 1.24; EL 0.12; SL 1.12; WL 1.68; PeL 0.66; PeW 0.48; HFeL 1.52; HTiL 1.24; HBaL 1.00; LS4 0.19; LT4 1.32; CI 86.1; ST 77.8; IGR 0.14.

Type Material
Baroni Urbani and de Andrade (2003) - Type locality: Baie d'Antongil, Madagascar. Type material: holotype and paratype workers labelled: "Iaraka, 1000 m, Baie d'Antongi1, 26.XI.1969, Madagascar, Prov. Tamatave, J. M. Betsch", in (holotype) and in  (paratype), both examined.

References based on Global Ant Biodiversity Informatics

 * Baroni Urbani C., and M.L de Andrade. 2003. The ant genus Proceratium in the extant and fossil record (Hymenoptera: Formicidae). Museo Regionale di Scienze Naturali, Monografie 36: 1-480.
 * Fisher B. L. 1997. Biogeography and ecology of the ant fauna of Madagascar (Hymenoptera: Formicidae). Journal of Natural History 31: 269-302.
 * Fisher B. L. 1998. Ant diversity patterns along an elevational gradient in the Réserve Spéciale d'Anjanaharibe-Sud and on the western Masoala Peninsula, Madagascar. Fieldiana Zoology (n.s.)90: 39-67.
 * Fisher B. L. 2003. Formicidae, ants. Pp. 811-819 in: Goodman, S. M.; Benstead, J. P. (eds.) 2003. The natural history of Madagascar. Chicago: University of Chicago Press, xxi + 1709 pp.