Holotype. Madagascar. • 1 major worker; Antsiranana; Sava Region: Parc National de Marojejy, near Manantenina tributary, 28.3 km 28.5°NE Andapa, forest along trail below Camp 1; -14.43934, 49.77689; alt. 450 m; 8 Feb 2018; B. L. Fisher et al. leg.; rainforest, ex rotten log; BLF40787; CASENT0825256 (CASC). Paratypes. • 2w., 1m.; same data as for holotype, CASENT0825255, CASENT0923288 (CASC, MHNG).

Moderately large species. Major workers. Head in full-face view sub-oval and slightly widening posteriorly, with anterior and posterior sides slightly convex, in lateral view sub-oval; ventral and dorsal faces convex; sides of the head with moderately sparse, long, suberect to erect pilosity; with thick, interrupted, dense, and longitudinal rugae, posteromedial frons with rugae irregular, interspaces with sparse rugofoveolate; lateral sides of frons with dense, thick, predominantly irregular rugae with few distinct, longitudinal rugae, interspaces with sparse rugulae; occipital lobes, area posterolateral from eyes without smooth notches; scape, when laid back, exceeding the midlength of head by two-fifths of its length; inner hypostomal teeth distinct, large, closely spaced, triangular, with rounded apex directed upward; outer hypostomal teeth lobe-like, wider than and approximately as high as inner teeth, apex directed upward; inner and outer hypostomal teeth closely spaced and not connected by concavity; mesosoma rugofoveolate; pronotum with additional thin, moderately dense, and transverse rugae; gaster smooth with slightly shagreened base of first tergite; body brown. Minor workers. Head foveolate; median frons with short and indistinct longitudinal rugulae; area posterolateral from eyes with weaker sculpture; scape, when laid back, exceeding the posterior head margin by one-third of its length; promesonotum low and moderately long, arched; promesonotal groove absent; propodeal spines small and triangular; mesosoma with sparse foveolae; dorsal promesonotum and medial parts of lateral sides of pronotum, propodeum, and katepisternum with smooth notches; body brown.

Major workers. Measurements (N = 1): HL: 1.03; HW: 1.0; SL: 0.74; EL: 0.15; WL: 0.96; PSL: 0.14; MTL: 0.65; PNW: 0.41; PTW: 0.13; PPW: 0.3; CI: 102.5; SI: 73.8; PSLI: 13.5; PPI: 42.8; PNI: 40.9; MTI: 65.3.

Head. In full-face sub-oval, slightly widening posteriorly, with anterior and posterior sides slightly convex (Fig. 47B). In lateral view sub-oval; ventral and dorsal faces convex; inner hypostomal teeth visible. Sides of the head with moderately sparse, long, suberect to erect pilosity; whole head with dense, long, decumbent to erect pilosity. Anteromedial part of frons with thick, interrupted, dense, and longitudinal rugae, posteromedial frons with irregular rugae, interspaces with sparse rugofoveolate; lateral sides of frons with dense, thick, and predominantly irregular rugae with few distinct longitudinal rugae, interspaces with sparse rugulae. Occipital lobes with irregular and thinner rugae and indistinctly rugulate interspaces. Area posterolateral from eyes with sparse, thick, longitudinal rugae and distinctly rugofoveolate interspaces. Gena with relatively sparse, thick, longitudinal rugae indistinctly rugulate interspaces. Centre of clypeus smooth and shiny, lateral sides with indistinct rugulae; median notch present, moderately wide, and shallow; median longitudinal carina present; lateral longitudinal carinae absent. Scape, when laid back, exceeding the midlength of head by two-fifths of its length; pilosity subdecumbent to erect (Fig. 47B, D). Inner hypostomal teeth distinct, large, closely spaced, triangular, with rounded apex directed upward; outer hypostomal teeth lobe-like, wider than and approximately as high as inner teeth, apex directed upward; inner and outer hypostomal teeth closely spaced and not connected by concavity (Fig. 64E). Mesosoma. In lateral view, promesonotum short, angular, and moderately low, posterior mesonotum moderately steep, mesonotal process indistinct, tubercle-like; promesonotal groove absent; metanotal groove indistinct; propodeal spines moderate, with wide base and acute apex; humeral area weakly produced (Fig. 47D). Surface shiny and rugofoveolate; pronotum with additional thin, moderately dense, and transverse rugae. Pilosity moderately dense, long, and erect (Fig. 47D, F). Petiole. Shiny with dense foveolae; node finely foveolate, triangular, with rounded and thick apex, in rear view node dorsoventrally slightly convex; pilosity moderately sparse and erect (Fig. 47D, F). Postpetiole. Shiny and foveolate; dorsum with reduced sculpture and smooth notch; in dorsal view oval, lateral margins medially with two dentate projections; pilosity long, moderately sparse, and erect (Fig. 47D, F). Gaster. Shiny and smooth with slightly shagreened base of first tergite; pilosity moderately dense, long, and erect (Fig. 47D, F). Colour. Brown, gaster slightly darker, legs yellowish (Fig. 47D, F).

Minor workers. Measurements (N = 2): HL: 0.56, 0.61; HW: 0.47, 0.48; SL: 0.74, 0.75; EL: 0.11, 0.12; WL: 0.75, 0.75; PSL: 0.09, 0.09; MTL: 0.54, 0.57; PNW: 0.32, 0.33; PTW: 0.08, 0.08; PPW: 0.13, 0.12; CI: 119.1, 126.6; SI: 156.8, 155.4; PSLI: 15.2, 14.5; PPI: 66.7, 66.1; PNI: 68.5, 69.5; MTI: 115.1, 119.7.

Head. Cephalic margin slightly convex (Fig. 47A). Pilosity relatively sparse, moderately long, subdecumbent to erect. Sculpture shiny and foveolate; median frons with short and indistinct longitudinal rugulae; area posterolateral from eyes with weaker sculpture; antennal sockets with few indistinct, curved outward rugae and foveolate interspaces. Clypeus with median longitudinal carina absent; two lateral longitudinal carinae absent. Scape, when laid back, exceeding the posterior head margin by one-third of its length; pilosity dense, subdecumbent to erect (Fig. 47A, C). Mesosoma. In lateral view, promesonotum low and moderately long, arched; promesonotal groove absent; metanotal groove distinct; propodeal spines small and triangular (Fig. 47C). Sculpture shiny with sparse foveolae; dorsal promesonotum and medial parts of lateral sides of pronotum, propodeum, and katepisternum with smooth notches. Pilosity very sparse, moderately long, and erect (Fig. 47C, E). Gaster. With sparse, erect pilosity (Fig. 47C, E). Colour. Brown, legs yellowish (Fig. 47C, E).

Malagasy for watercourse in reference to the river located close to the sampling site of the species.

The species was collected at 450 m in elevation, in rainforest. Nest was located in a rotten log.

Pheidole mivory sp. nov., described from Parc National de Marojejy in Antsiranana, has major workers with dense and thick rugae that are anteromedially longitudinal and posteromedially irregular, with distinctly rugofoveolate interspaces, and brown body colouration. Morphologically it is most similar to the parapatric P. joffreville sp. nov., known from Parc National Montagne d’Ambre in Antsiranana. Majors of both taxa are extremely similar and species separation should be supported by or based exclusively on minors. Majors of P. mivory sp. nov. differ from P. joffreville sp. nov. in indistinctly rugofoveolate interspaces on frons, and presence of longitudinal rugae on lateral sides of frons, and indistinctly shagreened sculpture of first gastral tergite; minor workers differ in mesosoma with sparse foveolae with dorsal promesonotum and medial parts of lateral sides of pronotum, propodeum, and katepisternum with smooth notches.