Holotype. Madagascar. • 1 major worker; Toliara; Anosy Region, Anosyenne Mts, 29.9 km NW Manantenina; -24.13894, 47.06804; alt. 750 m; 22 Feb 2015; B. L. Fisher et al. leg.; montane rainforest, under rootmat, on rock; BLF36257; CASENT0704453 (CASC). Paratype. • 1w.; same data as for holotype, CASENT0923274 (CASC).

Minute species. Major workers.HL < 1.1 mm and WL < 0.9 mm; head in full-face view sub-oval, slightly widening posteriorly, with anterior and posterior sides convex, in lateral view sub-oval; ventral and dorsal faces convex; body yellowish orange; sides of head with moderately dense, moderately long, decumbent to subdecumbent pilosity; entire head distinctly sculptured, medial part of frons with thick, longitudinal, and dense rugae and smooth to indistinctly rugulate interspaces, rugae more irregular and directed slightly outward on posteromedial part; scape, when laid back, reaching the midlength of head; promesonotum foveolate with sparse, thick to moderately thick, transverse to irregular rugae on dorsum; anepisternum, katepisternum, and propodeum with sparser foveolae; inner hypostomal teeth distinct, large, closely spaced, triangular, with rounded apex directed upward; outer hypostomal teeth lobe-like, wider than inner teeth and approximately the same height; inner and outer hypostomal teeth closely spaced and not connected by concavity; base of first gastral tergite smooth. Minor workers.HL < 0.5 mm and WL < 0.6 mm, scape, when laid back, exceeding the posterior head margin by one-fifth of its length; propodeal spines reduced to small tubercles; head relatively oval and entirely smooth; body yellow; mesosoma smooth.

Major workers. Measurements (N = 1): HL: 1.06; HW: 1.05; SL: 0.56; EL: 0.12; WL: 0.9; PSL: 0.13; MTL: 0.5; PNW: 0.5; PTW: 0.12; PPW: 0.32; CI: 101.2; SI: 53.7; PSLI: 12.4; PPI: 36.7; PNI: 47.4; MTI: 48.1.

Head. In full-face view sub-oval, slightly widening posteriorly, with anterior and posterior sides convex (Fig. 50B). In lateral view sub-oval; ventral and dorsal faces convex; inner hypostomal teeth visible. Sides of the head with moderately dense, moderately long, decumbent to subdecumbent pilosity; whole head with dense, long, decumbent to erect pilosity. Medial part of frons with thick, longitudinal, and dense rugae and smooth to indistinctly rugulate interspaces, rugae more irregular and directed slightly outward on posteromedial part; lateral sides with thick, sparse, and irregular rugae with distinctly rugulate interspaces. Occipital lobes with dense, irregular rugae and distinctly rugoreticulate interspaces. Area posterolateral from eyes with weaker sculpture, rugoreticulate. Gena with relatively dense, thick, and longitudinal rugae and smooth to rugoreticulate interspaces. Clypeus with smooth centre 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, reaching the midlength of head; pilosity subdecumbent to erect (Fig. 50B, D). Inner hypostomal teeth distinct, large, closely spaced, triangular, with rounded apex directed upward; outer hypostomal teeth lobe-like, wider than inner teeth and approximately the same height; inner and outer hypostomal teeth closely spaced and not connected by concavity (Fig. 64H). Mesosoma. In lateral view, promesonotum short, angular, and moderately high, posterior mesonotum moderately steep, mesonotal process very indistinct, bulge-like; promesonotal groove absent; metanotal groove absent; propodeal spines very short, with wide base and acute apex; humeral area produced (Fig. 50D). Surface shiny; promesonotum foveolate with sparse, thick to moderately thick, transverse to irregular rugae on dorsum; anepisternum, katepisternum, and propodeum with sparser foveolae. Pilosity moderately sparse, moderately long, and erect (Fig. 50D, F). Petiole. Shiny with dense foveolae; node finely foveolate, triangular, with rounded and thin apex, in rear view node dorsoventrally convex; pilosity moderately sparse and erect (Fig. 50D, 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. 50D, F). Gaster. Shiny and smooth; pilosity moderately dense, moderately short, and erect (Fig. 50D, F). Colour. Yellowish orange with yellow legs (Fig. 50D, F).

Minor workers. Measurements (N = 1): HL: 0.49; HW: 0.44; SL: 0.47; EL: 0.09; WL: 0.58; PSL: 0.06; MTL: 0.36; PNW: 0.29; PTW: 0.06; PPW: 0.11; CI: 113.0; SI: 107.8; PSLI: 12.8; PPI: 60.0; PNI: 67.0; MTI: 82.6.

Head. Cephalic margin indistinct and relatively straight (Fig. 50A). Pilosity relatively sparse, moderately long, decumbent to subdecumbent. 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 (Fig. 50A, C). Mesosoma. In lateral view, promesonotum moderately high and short, arched; promesonotal groove absent; metanotal groove distinct; propodeal spines reduced to small tubercles (Fig. 50C). Sculpture shiny and smooth. Pilosity moderately sparse, moderately long, and erect (Fig. 50C, E). Gaster. With sparse, erect pilosity (Fig. 50C, E). Colour. Yellow (Fig. 50C, E).

Latin for both small and gibbus, in reference to small body size and shape of promesonotum of major workers.

The species was collected at 750 m in elevation, in montane rainforest. Nest was located under rootmats, on rock.

Pheidole parvulogibba sp. nov. 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 sub-oval, slightly widening posteriorly with anterior and posterior sides convex in major workers, and minor workers with yellow to brown body colouration and head foveolate or predominantly smooth and relatively oval. The group includes six species: P. havoana sp. nov., P. kely sp. nov., P. parvula sp. nov., P. parvulogibba sp. nov., P. volontany sp. nov., and P. midongy sp. nov. Within this group, P. parvulogibba sp. nov., described from the Anosyenne Mts. in Toliara, is most similar to P. kely sp. nov., known from northern Madagascar, P. parvula sp. nov., known from the vicinity of Antananarivo, and sympatric P. havoana sp. nov. Minor workers of P. parvulogibba sp. nov. distinctly differ from P. kely sp. nov. and P. havoana sp. nov. in never foveolate head; and from P. parvula sp. nov. in entirely smooth frons and vertex. Major workers of P. parvulogibba sp. nov. differ from P. havoana sp. nov. and P. parvula sp. nov. in medial part of frons with thick, dense rugae and smooth to indistinctly rugulate interspaces; from P. kely sp. nov. in promesonotum foveolate with sparse, thick to moderately thick, transverse to irregular rugae on dorsum; anepisternum, katepisternum, and propodeum with sparser foveolae but never smooth notches.