Pheidole nitidobruna

The species was collected at 550 m in elevation, in rainforest. Nest was located in a rotten log.

Identification
Salata and Fisher (2020) - Minute species. Major: HL < 0.9 mm and WL < 0.8 mm; head in full-face view elongate, not widening posteriorly with posterior sides slightly convex, in lateral view sub-oval and short with convex dorsal and ventral sides; body brown; sides of head with moderately sparse, moderately long, suberect to erect pilosity; entire head distinctly sculptured, medial part of frons with thick and longitudinal rugae and smooth to indistinctly rugulate interspaces, occipital lobes with dense and irregular rugae with indistinctly rugoreticulate interspaces; scape, when laid back, exceeding the midlength of head by one-fifth of its length; lateral sides of promesonotum with smooth notches; inner hypostomal teeth distinct, moderate, closely spaced, triangular, with rounded apex directed upward; outer hypostomal teeth lobe-like, lower and wider than inner teeth; inner and outer hypostomal teeth closely spaced and not connected by concavity; base of first gastral tergite shagreened. Minor: HL < 0.45 mm and WL < 0.5 mm, scape, when laid back, exceeding the posterior head margin by one-fifth of its length; propodeal spines reduced to small tubercles; head relatively rectangular; body yellowish brown; head with frons and vertex smooth; mesosoma smooth.

Pheidole nitidobruna belongs to the group of species characterised by small body size (major workers: HL < 1.05 mm, WL < 0.9 mm and minor workers HL < 0.5 mm, WL < 0.6 mm), major workers with head elongate and not widening posteriorly, and minor workers with predominantly smooth and relatively rectangular head and yellow to brown body colouration. The group includes four species: Pheidole flavominuta, P. nitidobruna, Pheidole mikros, and Pheidole beanka. Pheidole nitidobruna is known only from Makirovana forest in Antsiranana and is parapatric with P. mikros, which is recorded from the area between Andapa and Antisiranana. Major workers of P. nitidobruna can be separated from P. mikros by smooth to indistinctly rugulate interspaces on frons and occipital lobes and presence of smooth notches on lateral sides of promesonotum. Minor workers of P. nitidobruna can be separated from P. mikros based on entirely smooth vertex and frons and presence of propodeal spines reduced to small tubercles.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 * . Pheidole nitidobruna Salata & Fisher, 2020: 123, figs. 48A–F, 64F, 66J (w.) MADAGASCAR.

Worker
Major (N = 1): HL: 0.9; HW: 0.79; SL: 0.53; EL: 0.1; WL: 0.79; PSL: 0.11; MTL: 0.46; PNW: 0.44; PTW: 0.11; PPW: 0.28; CI: 113.1; SI: 66.7; PSLI: 12.7; PPI: 37.9; PNI: 55.8; MTI: 57.4.

Head. In full-face view elongate, not widening posteriorly, with anterior and posterior sides slightly convex. In lateral view sub-oval; ventral and dorsal faces convex; inner hypostomal teeth visible. Sides of the head with moderately sparse, moderately long, suberect to erect pilosity; whole head with dense, long, decumbent to erect pilosity. Medial part of frons with thick, longitudinal, and moderately dense rugae and smooth to indistinctly rugulate interspaces, rugae directed slightly outward on posteromedial part; anterolateral sides with thick, sparse, and longitudinal rugae with smooth to indistinctly rugulate interspaces, posterolateral sides with dense, thick, and irregular rugae with distinctly rugulae interspaces. Occipital lobes with dense, irregular rugae and indistinctly rugoreticulate interspaces. Area posterolateral from eyes with weaker sculpture, rugoreticulate. Gena with relatively sparse, thick, and longitudinal rugae and smooth interspaces. Centre of clypeus smooth and shiny, lateral sides with indistinct rugulae; median notch present, moderately wide, and shallow; median longitudinal carina absent; lateral longitudinal carinae absent. Scape, when laid back, exceeding the midlength of head by one-fifth of its length; pilosity subdecumbent to erect. Inner hypostomal teeth distinct, moderate, closely spaced, triangular, with rounded apex directed upward; outer hypostomal teeth lobe-like, lower and wider than inner teeth; inner and outer hypostomal teeth closely spaced and not connected by concavity. Mesosoma. In lateral view, promesonotum short, angular, and moderately high, posterior mesonotum moderately steep, mesonotal process very indistinct, tubercle-like; promesonotal groove absent; metanotal groove absent; propodeal spines short, with wide base and acute apex; humeral area produced. Surface shiny; promesonotum with sparse, thick to moderately thick, irregular rugae and foveolate interspaces, lateral sides with smooth notches; anepisternum, katepisternum, and propodeum with denser rugofoveolae. Pilosity moderately sparse, moderately long, and erect. Petiole. Shiny with dense foveolae; node finely foveolate, triangular, with rounded and thin apex, in rear view node dorsoventrally concave; pilosity moderately sparse and erect. Postpetiole. Shiny and foveolate; dorsum with reduced sculpture and smooth notch; in dorsal view trapezoid, lateral margins medially with two distinct dentate projections; pilosity long, moderately sparse, and erect. Gaster. Shiny and smooth with shagreened base; pilosity moderately dense, moderately short, and erect. Colour. Brown with yellow legs.

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 = 1): HL: 0.44; HW: 0.38; SL: 0.42; EL: 0.08; WL: 0.5; PSL: 0.03; MTL: 0.31; PNW: 0.25; PTW: 0.06; PPW: 0.08; CI: 117.2; SI: 110.3; PSLI: 7.4; PPI: 75.4; PNI: 67.0; MTI: 82.3.

Head. Cephalic margin indistinctly relatively straight. Pilosity relatively sparse, moderately long, decumbent to suberect. Sculpture shiny and smooth; antennal sockets with few thick, curved outward rugae and smooth interspaces. Clypeus with median longitudinal carina absent; two lateral longitudinal carinae absent. Scape, when laid back, exceeding the posterior head margin by one-fifth of its length; pilosity dense, subdecumbent to erect. Mesosoma. In lateral view, promesonotum moderately high and short, arched; promesonotal groove absent; metanotal groove indistinct; propodeal spines reduced to small tubercles. Sculpture shiny and smooth. Pilosity moderately sparse, moderately long, and erect. Gaster. With sparse, erect pilosity. Colour. Yellowish brown, legs and antenna 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
Holotype. Madagascar. 1 major worker; Antsiranana; Makirovana forest; -14.16044, 49.95216; alt. 550 m; 1 May 2011; B. L. Fisher et al. leg.; rainforest, ex rotten log; BLF26855; CASENT0923273. Paratype. 1w.; same data as for holotype, CASENT0245024 (CASC).

Etymology
Latin for smooth and brown in reference to smooth sculpture and dark body colouration.