Pheidole mikros

The species was collected between 80-450 m in elevation, in rainforest and tropical dry forest. Nests were located in rotten logs and under tree bark.

Identification
Salata and Fisher (2020) - A member of the Pheidole sikorae species group. Minute species. Major: HL < 0.9 mm and WL < 0.75 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 brownish orange; sides of head with moderately sparse, moderately long, subdecumbent to suberect pilosity; entire head distinctly sculptured, medial part of frons with thick and longitudinal rugae and indistinctly rugulate and never smooth interspaces, occipital lobes with dense and irregular rugae with distinctly rugoreticulate interspaces; scape, when laid back, slightly exceeding the midlength of head; lateral sides of promesonotum distinctly foveolate with additional sparse and indistinct rugulae; inner hypostomal teeth large, closely spaced, triangular, with rounded apex directed upward; outer hypostomal teeth lobe-like, slightly lower and narrower than inner teeth; inner and outer hypostomal teeth moderately closely spaced and not connected by concavity; base of first gastral tergite shagreened. Minor: HL < 0.5 mm and WL < 0.6 mm, scape, when laid back, surpassing the posterior head margin by one-fifth of its length; propodeal spines small, triangular; head relatively rectangular; body yellowish brown; lateral sides of frons with fine, sparse, and irregular rugulae with smooth interspaces; vertex with distinct, sparse, and transverse rugulae; mesosoma with sparse and moderately thick network of irregular rugulae; mesonotum and katepisternum smooth.

Pheidole mikros 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), head elongate and not widening posteriorly in major workers, and minor workers with head predominantly smooth and relatively rectangular, and body colouration yellow to brown. The group includes four species: Pheidole flavominuta, Pheidole nitidobruna, P. mikros, and Pheidole beanka Pheidole mikros is known from the area between Andapa and Antisiranana and is parapatric with Pheidole nitidobruna described from Makirovana forest in Antsiranana. Major workers of P. mikros can be separated from P. nitidobruna by predominantly indistinctly rugulate interspaces on frons, occipital lobes with distinctly foveolate or rugoreticulae interspaces, and absence of smooth notches on lateral sides of promesonotum. Minor workers of P. mikros can be separated from P. nitidobruna based on presence of sculpture on vertex and frons and presence of small, triangular propodeal spines. However, the morphology of P. mikros is most similar to P. beanka, which is known from Réserve forestière Beanka in Mahajanga. Pheidole mikros differs from P. beanka by the combination of the following characters: major workers have medial part of frons with indistinctly rugulate interspaces and their propodeal spines are moderately long; minor workers have lateral sides of frons with fine, sparse, and irregular rugulae, mesosoma covered by a sparse and moderately thick network of irregular rugulae, and body is yellowish brown.

Distribution based on Regional Taxon Lists
Malagasy Region: Madagascar.

Nomenclature

 * . Pheidole mikros Salata & Fisher, 2020: 117, figs. 46A–F, 64D, 66H (w.) MADAGASCAR.

Worker
Major (N = 2): HL: 0.86, 0.88; HW: 0.8, 0.83; SL: 0.49, 0.47; EL: 0.12, 0.11; WL: 0.74, 0.77; PSL: 0.12, 0.13; MTL: 0.44, 0.41; PNW: 0.46, 0.46; PTW: 0.13, 0.14; PPW: 0.35, 0.37; CI: 107.6, 105.2; SI: 61.7, 56.5; PSLI: 13.9, 15.0; PPI: 37.8, 38.7; PNI: 57.3, 55.6; MTI: 54.8, 49.7.

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, subdecumbent to suberect pilosity; whole head with dense, long, decumbent to erect pilosity. Medial part of frons with thick, longitudinal, and dense rugae and indistinctly rugulate interspaces, rugae more irregular and directed slightly outward on posteromedial part; lateral sides with thick, sparse, and predominantly longitudinal rugae, interspaces shiny and distinctly foveolate. Occipital lobes with denser, irregular rugae and distinctly foveolate interspaces. Area posterolateral from eyes foveolate with sparse and moderately thick rugae. Gena with relatively sparse, thick, and longitudinal rugae and indistinctly foveolate 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, slightly exceeding the midlength of head; pilosity subdecumbent to erect. Inner hypostomal teeth distinct, large, closely spaced, triangular, with rounded apex directed upward; outer hypostomal teeth lobe-like, slightly lower and narrower than inner teeth; inner and outer hypostomal teeth moderately closely spaced and not connected by concavity. Mesosoma. In lateral view, promesonotum short, angular, and moderately low, posterior mesonotum moderately steep, mesonotal process very indistinct, tubercle-like; promesonotal groove absent; metanotal groove absent; propodeal spines moderately long, with wide base and acute apex; humeral area laterally weakly produced. Surface shiny and distinctly foveolate with additional sparse and indistinct rugulae on promesonotum. Pilosity moderately sparse, moderately long, and erect. Petiole. Shiny with dense foveolae; node smooth to finely foveolate, triangular, with rounded and thick apex, in rear view node dorsoventrally concave; pilosity moderately sparse and erect. Postpetiole. Shiny and foveolate; dorsum with slightly reduced sculpture; in dorsal view trapezoid, lateral margins medially with two large dentate lobes; pilosity long, moderately sparse, and erect. Gaster. Shiny, its base shagreened; pilosity dense, moderately short, and erect. Colour. Brownish orange; mandibles and gaster brown.

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 = 3): HL: 0.47-0.48 (0.47); HW: 0.4-0.42 (0.41); SL: 0.42-0.43 (0.43); EL: 0.08-0.08 (0.08); WL: 0.54-0.56 (0.55); PSL: 0.07-0.07 (0.07); MTL: 0.3-0.31 (0.31); PNW: 0.29-0.3 (0.29); PTW: 0.07-0.07 (0.07); PPW: 0.12-0.13 (0.12); CI: 110.8-117.7 (115.1); SI: 101.9-105.4 (104.2); PSLI: 14.4-15.5 (15.0); PPI: 54.7-57.5 (56.4); PNI: 67.7-73.7 (71.6); MTI: 73.4-76.0 (74.4).

Head. Cephalic margin indistinctly concave to straight. Pilosity relatively dense, moderately long, decumbent to suberect. Sculpture shiny; medial frons smooth; lateral sides of frons with fine, sparse, and irregular rugulae with smooth interspaces; vertex with distinct, sparse, and transverse rugulae; area posterolateral from eyes with fine, sparse, and irregular rugulae with smooth interspaces; antennal sockets with few thick, curved outward rugae and indistinctly foveolate 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, subdecumbent to erect. Mesosoma. In lateral view, promesonotum moderately high and short, arched; promesonotal groove absent; metanotal groove distinct; propodeal spines small and triangular. Sculpture shiny with sparse and moderately thick network of irregular rugulae; mesonotum and katepisternum 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; Sakaramy; -12.44131, 49.22723; alt. 365 m; 13 May 2011; B. L. Fisher et al. leg.; tropical dry forest, under tree bark, live tree; BLF27321; CASENT0923271. Paratype. 1w.; same data as for holotype, CASENT0261101 (CASC).

Etymology
Greek for small in reference to the body size.