Pheidole sikorae

The species was collected between 20-1580 m in elevation, in montane and littoral rainforest. Nests were located in rotten logs, dead twigs above ground, under moss, and rot pockets above ground.

Identification
Salata and Fisher (2020) - Moderately large species. Major: Head in full-face view sub-oval, widening posteriorly, with anterior and posterior sides convex, in lateral view sub-oval; ventral and dorsal faces convex; impressed and smooth concavity placed lateral to antennal socket and tentorial pit present; sides of the head with dense, long, suberect to erect pilosity; anterior and medial parts of frons with sparse, thick, longitudinal, and sometimes interrupted rugae and smooth to indistinctly rugulae interspaces; posterolateral sides with more irregular rugae and smooth to indistinctly rugulate interspaces, area posterolateral from eyes without smooth notches; scape, when laid back, exceeding the midlength of head by approximately one-third of its length; inner hypostomal teeth distinct, moderately high, closely spaced, triangular, with rounded apex and wide base; outer hypostomal teeth lobe-like, wider and higher than inner hypostomal teeth, apex directed outward; inner and outer hypostomal teeth closely spaced and connected by concavity; promesonotum predominantly smooth, with sparse, thin to thick, transverse rugae on pronotum and sometimes with fine, irregular rugulae on anepisternum and katepisternum; propodeum with fine, sparse, and indistinct rugulae; gaster smooth; body yellow to orange. Minor: Head sculpture variable, from smooth with foveolae restricted to anterior or medial frons to foveolate with smooth patches on vertex and area posterolateral from eyes; foveolae always sparse, frons sometimes with additional, sparse, and irregular rugae; scape, when laid back, surpassing the posterior head margin by one-fifth of its length; promesonotum moderately high and short; promesonotal groove present; propodeal spines very small and triangular; mesosoma smooth and shiny, only dorsum with few transverse, thick rugulae and propodeum with indistinct and sparse foveolae; body yellow to orange.

Major workers of Pheidole sikorae can be easily separated from all other Malagasy Pheidole based on strongly reduced sculpture of mesosoma and presence of impressed and smooth concavity placed lateral to antennal socket and tentorial pit. However, minor workers of P. sikorae have highly variable head sculpture. In most cases the head is predominantly smooth with sparse foveolae restricted to anterior and medial frons, but sometimes sparse foveolae extend to the whole frons and smooth patches are present only on vertex and area posterolateral from eyes. Minors of P. sikorae with strongly developed head sculpture are indistinguishable from minor workers of Pheidole antranohofa, a species known from Parc National de Marojejy in Antsiranana. Distribution ranges of these taxa do not overlap.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 *  sikorae. Pheidole sikorae Forel, 1891b: 223 (s.w.) MADAGASCAR. Forel, 1892l: 258 (q.). Current subspecies: nominal plus litigiosa.

Worker
Major (N = 10): HL: 0.94-1.18 (1.11); HW: 0.93-1.19 (1.14); SL: 0.65-0.7 (0.67); EL: 0.12-0.15 (0.14); WL: 0.9-1.07 (1.01); PSL: 0.13-0.19 (0.16); MTL: 0.59-0.69 (0.66); PNW: 0.39-0.5 (0.47); PTW: 0.13-0.15 (0.14); PPW: 0.23-0.3 (0.27); CI: 94.2-101.4 (97.3); SI: 55.6-69.7 (59.3); PSLI: 12.1-15.7 (14.5); PPI: 42.5-55.4 (50.1); PNI: 40.0-42.2 (41.5); MTI: 54.4-63.7 (57.7).

Head. In full-face view sub-oval, widening posteriorly, with anterior and posterior sides convex. In lateral view sub-oval; ventral and dorsal faces convex; inner hypostomal teeth invisible. Sides of the head with dense, long, suberect to erect pilosity; whole head with relatively dense, long, decumbent to erect pilosity. Anterior and medial parts of frons with sparse and thick, longitudinal, and sometimes interrupted rugae and smooth to indistinctly rugulate interspaces; posterolateral sides with more irregular rugae and smooth to indistinctly rugulate interspaces. Impressed and smooth concavity placed lateral to antennal socket and tentorial pit present. Occipital lobes with thick, sparse, irregular rugae, sometimes fading medially, interspaces smooth or with fine, indistinct rugulae. Gena with sparse, thick, and longitudinal rugae and smooth interspaces. Area posterolateral from eyes with weaker and sparser rugoreticulae. Centre of clypeus smooth and shiny, lateral sides with indistinct rugulae; median notch present, wide, and shallow; median longitudinal carina absent; lateral longitudinal carinae absent. Scape, when laid back, exceeding the midlength of head by approximately one-third of its length; pilosity decumbent to suberect. Inner hypostomal teeth distinct, moderately high, closely spaced, triangular, with rounded apex and wide base; outer hypostomal teeth lobe-like, wider and higher than inner hypostomal teeth, apex directed outward; inner and outer hypostomal teeth closely spaced and connected by concavity. Mesosoma. In lateral view, promesonotum short, angular, and moderately high, posterior mesonotum moderately steep, mesonotal process indistinct, tubercle-like; promesonotal groove absent; metanotal groove present; propodeal spines moderate, triangular, thin, with acute apex; humeral area laterally weakly produced. Surface shiny, promesonotum predominantly smooth, with sparse, thin to thick, transverse rugae on pronotum and sometimes with fine, irregular rugulae on anepisternum and katepisternum; propodeum with fine, sparse, and indistinct rugulae. Pilosity sparse, long, and erect. Petiole. Shiny with fine and sparse rugulae; peduncle; node smooth to indistinctly rugulose, low, triangular, with rounded apex, in rear view node dorsoventrally convex; pilosity moderately sparse and erect. Postpetiole. Shiny, with fine and sparse rugulae; in dorsal view postpetiole oval, lateral margins medially with two dentate projections; pilosity long, moderately sparse, and erect. Gaster. Shiny and smooth; pilosity sparse, long, and erect. Colour. Yellow to orange; gaster usually slightly darker.

The following characters are found in most Pheidole sikorae species-group majors in Madagascar (Salata and Fisher 2020b). These characters also occur in , except for any differences noted in the paragraph above. Dorsal face of head in lateral view not depressed posteriorly; antennal sockets shallow; frontal lobes absent; head in full-face view with distinct median concavity; antenna 12-segmented, with 3-segmented club; masticatory margin of mandible with large, stout apical and preapical teeth, followed by a long diastema and then a short and crenulate tooth just before the rounded basal angle; outer surface of mandible mostly smooth and shining, sometimes with weak and sparse foveolae; antennal scrobes absent; promesonotum strongly convex, well above the level of propodeum; petiolar peduncle with small horizontal lobes on its basal part; postpetiole short with slightly convex dorsum; petiolar peduncle without horizontal lobes on its basal part; body unicolourous.

Minor (N = 10): HL: 0.55-0.61 (0.58); HW: 0.46-0.51 (0.49); SL: 0.58-0.63 (0.61); EL: 0.1-0.12 (0.11); WL: 0.67-0.76 (0.72); PSL: 0.06-0.08 (0.07); MTL: 0.45-0.53 (0.48); PNW: 0.3-0.35 (0.33); PTW: 0.07-0.09 (0.08); PPW: 0.13-0.16 (0.14); CI: 114.4-120.7 (118.4); SI: 121.9-127.5 (124.6); PSLI: 10.3-14.0 (11.8); PPI: 49.3-69.0 (60.6); PNI: 64.9-68.8 (67.5); MTI: 94.4-103.9 (98.9).

Head. Cephalic margin straight or indistinctly convex. Pilosity moderately dense, long, and erect. Head sculpture variable, from smooth with foveolae restricted to anterior or medial frons to foveolate with smooth patches on vertex and area posterolateral from eyes; foveolae always sparse, frons sometimes with additional, sparse, and irregular rugae; antennal sockets with few thick, curved outward rugae and smooth to foveolae interspaces. Clypeus with median longitudinal carina absent; two lateral longitudinal carinae absent. Scape, when laid back, surpassing the posterior head margin by one-fifth of its length; pilosity dense, suberect to erect. Mesosoma. In lateral view, promesonotum moderately high, short, arched; promesonotal groove present, sometimes indistinct; metanotal groove present and distinct; propodeal spines very small and triangular, apex acute. Sculpture smooth and shiny, only dorsum with few transverse, thick rugulae and propodeum with indistinct and sparse foveolae. Pilosity sparse, moderately long, and erect. Petiole. Peduncle short and thin with ventral face slightly convex(Fig. 53C, E). Postpetiole. Short, low, and convex; with few short, erect setae. Gaster. With sparse, erect pilosity. Colour. Orange to yellow.

The following characters are found in most Pheidole sikorae species-group minors in Madagascar (Salata and Fisher 2020b). These characters also occur in , except for any differences noted in the paragraph above. Antennal sockets shallow; frontal lobes absent; occipital carina absent; head in full-face view oval, posterior and anterior of eyes convex; antenna 12-segmented, with 3-segmented club; humeral area not developed; clypeus smooth and shiny, its anterior margin regularly convex; promesonotum well above the level of propodeum; petiole smooth, with node moderately low, triangular, and small, with few short, erect setae; petiolar peduncle with ventral face slightly convex; postpetiole smooth, short, low, and slightly convex, with few short, erect setae; gaster smooth and shiny; body unicolourous.

Type material
Pheidole sikorae Forel, 1891: 223 (s.w.). Lectotype [designated here]: major worker (top specimen, CASENT0101692): Madagascar, Antananarivo, Andrangoloaka, coll. Sikora [examined]. Paralectotypes: 1 major worker (CASENT0876548, bottom specimen, the same pin as lectotype) (MHNG) [examined], 3 minor workers (CASENT0101668) (MHNG) [examined].

References based on Global Ant Biodiversity Informatics

 * 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. 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.
 * Wheeler W. M. 1922. Ants of the American Museum Congo expedition. A contribution to the myrmecology of Africa. IX. A synonymic list of the ants of the Malagasy region. Bulletin of the American Museum of Natural History 45: 1005-1055