Polyrhachis fornicata

Specimens have been collected in fogging samples from cacao agroforest.

Identification
Kohout (2008) surmised, despite the types being lost, this apparently endemic Sulawesi species was distinctively enough described by Emery to allow non-type specimens to be identified as Polyrhachis fornicata.

Polyrhachis celebensis is very similar to Polyrhachis fornicata. Both species have a virtually identical petiole with slender and acute dorsal spines with their tips curved backwards, while the lateral spines are very short, reduced to mere angles. In lateral view the mesosoma of both species is quite similar, featuring a moderately convex pronotum and a distinct step in the mesosomal outline, indicating the position of the metanotal groove. However, the propodeal declivity in P. celebensis is steeply oblique, while in P. fornicata it is virtually vertical. The main difference between the species is the shape of their pronotal humeri that, in P. celebensis are somewhat angulate, while in P. fornicata they are narrowly rounded.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia, Sulawesi.

Nomenclature

 *  fornicata. Polyrhachis rastellata subsp. fornicata Emery, 1900d: 720 (w.) INDONESIA (Sulawesi). Combination in P. (Cyrtomyrma): Emery, 1925b: 208. Raised to species: Donisthorpe, 1938c: 261; Dorow, 1995: 23. See also: Kohout, 2008a: 261.

Worker
Kohout (2008) - TL c. 6.00-6.50; HL 1.53-1.62; HW 1.50-1.65; CI 98-100; SL 1.78-1.96; SI 119-121; PW 1.18-1.34; MTL 2.09-2.25 (4 measured).

Anterior clypeal margin produced into a shallow, truncate, medially notched flange, flanked by distinct acute angles. Clypeus in profile weakly convex; medially with blunt, longitudinal carina; basal clypeal margin weakly impressed medially, not impressed laterally. Frontal triangle indistinct. Frontal carinae with margins moderately raised medially; weakly converging and rather flat posteriorly; central area concave with weakly impressed, short, frontal furrow. Sides of head in front of eyes converging towards mandibular bases in almost straight line; behind eyes sides rounding abruptly into convex occipital margin. Eyes convex, in full face view clearly breaking lateral cephalic outline. Ocelli lacking; their relative positions indicated by distinct punctures in sculpturation. Pronotal dorsum in dorsal view with greatest width just behind narrowly rounded humeri; moderately convex in lateral view with promesonotal suture well impressed; position of metanotal groove indicated by distinct step in outline and a shallow depression. Propodeal dorsum rounding smoothly into vertical, declivity. Petiole with anterior face virtualy flat, posterior face weakly convex; dorsal spines situated close together, slender and acute, somewhat diverging with their tips curved backwards; lateral spines very short, reduced to mere angles in some specimens. Subpetiolar process in lateral view relatively short, acute anteriorly, with posterior face weakly concave. Anterior face of first gastral segment lower than full height of petiole, widely rounding onto dorsum of gaster.

Mandibles very finely rugose with numerous piliferous pits. Head, mesosoma and gaster shagreened; intensity of sculpturation only marginally increasing laterally, becoming somewhat reticulate, with meso-and metapleurae and base of petiole only weakly reticulate-rugose. Whole body with numerous piliferous pits and shallow punctures.

Mandibular masticatory borders near outer margins with numerous, curved hairs. Anterior clypeal margin with three, relatively long, anteriorly directed setae medially and a few, short setae laterally. Only a few pairs of rather short, erect hairs near anterior and basal clypeal margins, along frontal carinae and a pair of longer hairs on vertex. A few longer, erect hairs on anterior and posterior faces of fore coxae. Gaster with several erect hairs along posterior margins of dorsal segments and longer and more abundant hairs over ventral surfaces.

Colour. Black throughout, only tips of mandibular teeth, antennal condylae, extreme tip of apical funicular segments, joints of trochaters and femora, and tarsal claws lighter, yellowish-or reddish-brown.

Type Material
Kohout (2008) - Syntype workers. INDONESIA, SULAWESI (E. Modigliani), (type/s considered lost).

This species was originally described from Sulawesi by Emery (1900) as a subspecies of Polyrhachis rastellata and also listed from the island the following year (Emery, 1901). The type specimen/s from Sulawesi should be lodged in the Emery collection in MCSN, however, an extensive search by Dr Roberto Poggi and the author failed to locate them in that, or any other collection examined. Consequently, specimens collected by Elio Modigliani on Sumatra, Engano (= Pulau Enggano) and Mentawei (= Kepulauan Mentawai), lodged in MCSN and labelled as ‘Co-types’, have been generally accepted as syntypes of this species. These specimens were listed in the original description (Emery, 1900) and bear identification tags inscribed ‘Polyrhachis rastellata fornicata Em’ in Emery’s handwriting. However, I have directly compared the ‘Co-type’ specimens from Sumatra (Balighe, x.90-iii.91, E. Modigliani) with recently acquired Cyrtomyrma specimens from Sulawesi and am confident that they represent two different species. The original description of P. fornicata, though rather short, is diagnostic and no other Cyrtomyrma species known to occur on Sulawesi share the characters given by Emery.