Carebara omasi Azorsa & Fisher

Azorsa, Frank & Fisher, Brian L., 2018, Taxonomy of the ant genus Carebara Westwood (Formicidae, Myrmicinae) in the Malagasy Region, ZooKeys 767, pp. 1-149 : 1

Carebara omasi Azorsa & Fisher sp. n.

Holotype.

(major worker), MADAGASCAR, Toliara , Réserve Spéciale d’Ambohijanahary, Forêt d’Ankazotsihitafototra, 34.6 km 314° NW Ambaravaranala, -18.26, 45.41833, 1100 m, montane rainforest, 16.i.2003, (Fisher, Griswold et al.). Collection code BLF07086, (CASC: CASENT0028870). Paratypes: (30 major workers and 16 minor workers), with same data as holotype, 17 major workers (BMNH: CASENT0028980, CASC: CASENT0029010, CASENT0029145, CASENT0028999, CASENT0029011, CASENT0029140, CASENT0028973, CASENT0028998, CASENT0029040, CASENT0029146, CASENT0029024, CASENT0028886, CASENT0028879, CASENT0028869, MCZ: CASENT0028945, MHNG: CASENT0028955, NHMB: CASENT0028987), and 16 minor workers (BMNH: CASENT0028987, CASC: CASENT0028928, CASENT0029047, CASENT0029035, CASENT0028947, CASENT0029042, CASENT0029043, CASENT0029045, CASENT0029046, CASENT0028936, CASENT0029031, CASENT0029087, CASENT0028940, MCZ: CASENT0028940, MHNG: CASENT0029086, NHMB: CASENT0029088). 13 major workers from: Toliara , Réserve Spéciale d’Ambohijanahary, Forêt d’Ankazotsihitafototra, 35.2 km 312° NW Ambaravaranala, -18.26667, 45.40667, 1050 m, montane rainforest, 13-17.i.2003, (Fisher, Griswold et al.), BLF07020, 4 major workers (CASC: CASENT0027925, CASENT0027900, CASENT0027924, CASENT0027810), BLF07132, 1 major worker (CASC: CASENT0496795), BLF07148, 2 major workers (CASC: CASENT0485919, CASENT0485920).

Diagnosis.

Antennae ten-segmented. Major: Head nearly subrectangular, longer than wide, lateral margins straight and parallel, posterolateral corners well developed and rounded, posterior margin of head deeply concave; dorsum of propodeum flat, posterodorsal corner with a pair of triangular teeth; gaster with very short decumbent or appressed hairs, and sparse, longer suberect hairs. Minor: Head longer than wide, posterior margin of head nearly straight; dorsum of propodeum weakly convex, posterodorsal corner with a pair of laminate, small, upwardly directed triangular teeth; gaster with short decumbent hairs and sparse, longer suberect to subdecumbent hairs.

Description of major workers.

Measurements (n=20): HL 0.62-1.10 (1.04); HW 0.54-0.94 (0.87); SL 0.27-0.42 (0.38); ML 0.15-0.27 (0.23); EL 0.01-0.15 (0.05); EM 0.18-0.29 (0.28); HD 0.36-0.68 (0.65); WL 0.52-1.02 (0.92); PSL 0.07-0.15 (0.13); PW 0.31-0.58 (0.55); MFL 0.30-0.58 (0.54), MFW 0.08-0.13 (0.12); MTL 0.24-0.46 (0.43), PTL 0.20-0.37 (0.35); PNL 0.07-0.14 (0.12); PTH 0.15-0.28 (0.24); PTW 0.13-0.24 (0.22); PPL 0.12-0.23 (0.19); PPNL 0.11-0.20 (0.17); PPH 0.08-0.26 (0.25); PPW 0.18-0.33 (0.30); GL 0.43-1.01 (0.92); GW 0.39-0.87 (0.80); CI 82-89 (84); MI 22-27 (22); SI 37-47 (37); MLI 55-64 (62); PPLI 54-67 (54); PPI 125-143 (136); PSI 12-16 (15).

Head slightly longer than wide (CI 82-89), in full-face view nearly subrectangular, about 1.2 times longer than wide. Posterior margin of head deeply concave, posterolateral corners well developed and rounded, lateral margins straight and parallel. Mandibles with six teeth. Anterior margin of clypeus nearly straight, and laterally convex. Ocelli present or absent. Antennae with ten segments. Scapes short (HL 0.62-1.10, SL 0.27-0.42, SI 0.01-0.15). Eyes present, consisting of one to 15 ommatidia (EL 0.01-0.15). Supraclypeal area triangular and well defined.

In profile view, posterolateral corner of head with a small angulate tooth resembling a horn. Promesonotum high and nearly rounded, promesonotal suture present or absent, when present, weakly impressed on dorsum, metanotal groove deeply impressed. Propodeum lower than promesonotum, and about 1.5 times higher than long, dorsal face of propodeum flat and declining posteriorly, posterodorsal corners of propodeum each armed with an acute triangular tooth, declivity concave with thin lateral laminae. Propodeal lobes triangular. Propodeal spiracle nearly oval and situated slightly above mid-height of sclerite, and beyond mid-length of sclerite by about half the diameter of the spiracle, distance from propodeal spiracle to posterodorsal corner of propodeum almost 3.2 times the diameter of the spiracle (PSL 0.04-0.07), and distance to declivity about 2.2 times the diameter of the spiracle. In dorsal view, promesonotum about as long as wide, anterior margin and sides rounded, and narrowed posteriorly; sides of propodeum straight.

Petiole longer than high (PTL 0.20-0.37, PTH 0.15-0.28) and with relatively long peduncle, ventral face weakly convex at center. Combined outline of dorsal surface of peduncle and anterior face of node nearly straight, weakly concave, posterior face of node vertical and slightly convex, anterodorsal corner weakly convex, posterodorsal corner rounded, dorsum narrow and rounded. Subpetiolar process produced as a small denticle, slightly smaller than the diameter of the propodeal spiracle. Postpetiolar node rounded and lower than petiolar node. In dorsal view, petiolar node almost as wide as postpetiolar node (PTW 0.13-0.24, PPW 0.18-0.33) and petiolar node wider than long (PNL 0.07-0.14, PTW 0.13-0.24), anterior margin of petiole weakly concave, and concave in postpetiole, posterior margin of petiole and postpetiole straight, sides rounded in petiole and postpetiole.

Dorsal surface of mandibles, clypeus and frons smooth and shiny, with scattered piligerous punctae on head and mandibles. Head with fine longitudinal rugae directed to posterior margin of head, and rugoreticulate close to posterior margin of head. Posterolateral portion of cephalic dorsum smooth and shiny. Sides of pronotum finely areolate, mesonotum and anepisternum smooth and shiny, katepisternum and metapleuron areolate-rugose. Pronotum finely areolate. Petiole, ventral face and sides of postpetiole areolate. In dorsal view, promesonotum, postpetiole and gaster smooth and shiny, propodeum and petiole areolate.

Lateral margins of head with short appressed hairs and long erect to suberect hairs, posterior margin with subdecumbent hairs. Scapes with appressed hairs. Outer margin of mandibles with short appressed hairs. Mesosoma with short suberect hairs and long erect hairs. Petiole and postpetiole with short decumbent hairs and long subdecumbent hairs. Tibia with appressed hairs. Gaster with short to very short appressed or decumbent hairs and dispersed, long suberect hairs. Color yellowish ferruginous.

Description of minor workers.

Measurements (n=9): HL 0.35-0.43; HW 0.31- 0.38; SL 0.21-0.27; ML 0.09-0.11; EL 0.02; EM 0.09-0.12; HD 0.21-0.27; WL 0.35-0.44; PSL 0.04-0.06; PW 0.19-0.24; MFL 0.22-0.28; MFW 0.05-0.07; MTL 0.15-0.21, PTL 0.12-0.15; PNL 0.06-0.08; PTH 0.10-0.13; PTW 0.08-0.11; PPL 0.07-0.10; PPNL 0.06-0.09; PPH 0.07-0.09; PPW 0.11-0.14; GL 0.30-0.42, GW 0.22-0.32; CI 86-93; MI 23-26; SI 60-65; MLI 66-78, PPLI 57-77; PPI 120-147; PSI 11-15.

Head slightly longer than wide (CI 86-93), in full-face view nearly subquadrate, about 1.1 times longer than wide. Posterior margin of head nearly straight, weakly concave, posterolateral corners rounded, lateral margins convex. Mandibles with five teeth. Anterior margin of clypeus slightly concave, nearly straight, and laterally angulate. Antennae with ten segments. Scape fails to reach posterior margin of head (HL 0.35-0.43, SL 0.21-0.27, SI 60-65). Eyes present, consisting of one ommatidium (EL 0.02). Supraclypeal area triangular but poorly defined.

In profile, promesonotum weakly convex, nearly flat, metanotal groove deeply impressed. Propodeum about 1.4 times higher than long, dorsal face of propodeum slightly convex, and declining posteriorly, propodeum armed, posterodorsal corners each armed with a laminate triangular and small tooth, declivity weakly convex, nearly flat, with thin lateral laminae. Propodeal lobes triangular. Propodeal spiracle rounded and situated above mid-height of sclerite by about 1.5 times the diameter of the spiracle, and beyond mid-length of sclerite by about two times the diameter of the spiracle, distance from propodeal spiracle to posterodorsal corner of propodeum almost twice the diameter of the spiracle (PSL 0.04-0.06), and distance to declivity same as the diameter of the spiracle. In dorsal view, promesonotum about 1.1 times longer than wide, anterior margin weakly convex, sides convex and narrowed posteriorly; sides of propodeum weakly convex.

Petiole longer than high (PTL 0.12-0.15, PTH 0.10-0.13) and with relatively long peduncle, ventral face medially convex. Combined outline of dorsal surface of peduncle and anterior face of node medially concave, posterior face of node slightly convex, anterodorsal and posterodorsal corner rounded, dorsum convex. Subpetiolar process produced as a small denticle, almost the same as half the diameter of the propodeal spiracle. Postpetiolar node nearly rounded and lower than petiolar node. In dorsal view, postpetiolar node wider than petiolar node (PTW 0.08-0.11, PPW 0.11-0.14), and petiolar node wider than long (PNL 0.06-0.08, PTW 0.08-0.11), anterior and posterior margins of petiole and postpetiole nearly straight, sides rounded in petiole and postpetiole.

Dorsal surface of head, mandibles, and clypeus smooth and shiny with scattered piligerous punctae on head and mandibles. Gena and frontal lobes with short longitudinal rugae. Mesosoma smooth and shiny except for mesopleuron and propodeum (areolate) and metapleuron (areolate-rugose). Petiole and ventral face of postpetiole areolate. In dorsal view, promesonotum, postpetiole and gaster smooth and shiny, propodeum and petiole areolate.

Lateral margins of head with decumbent hairs, posterior margin with subdecumbent hairs. Scapes with appressed hairs. Outer margin of mandibles with decumbent hairs. Mesosoma with short and long suberect hairs. Petiole and postpetiole with short appressed hairs and longer subdecumbent hairs. Tibia with appressed hairs. Gaster with short decumbent to appressed hairs and long subdecumbent hairs. Color yellowish ferruginous.

Distribution and biology.

Carebara omasi was collected in the central and southwestern parts of Madagascar (Figure 69). This species occurs in disturbed gallery montane forest, montane rainforest and Uapaca woodland, and was collected at elevations ranging from 1050 m to 1491 m. Individuals and colonies were found in rotten logs, leaf mold and rotten wood. They were collected using maxi-Winkler traps.

Comments.

Carebara omasi can be confused with C. nosindambo but can be separated by the sculpture of the posterolateral portion of the cephalic dorsum, which is lacking sculpture in C. omasi and is sculptured in C. nosindambo . C. omasi is present only in central and southwestern areas of Madagascar while C. nosindambo is widespread throughout most of Madagascar. C. omasi is endemic to the center of Madagascar, but there are also records from southwestern Madagascar, other six species were recorded at the same localities: C. bara , C. betsi , C. grandidieri , C. hiragasy , C. nosindambo , and C. sampi .

C. omasi have three intermediates in the major worker subcaste (Figure 56). The shape of the posterolateral corner and posterior margin of the head varies little among all intermediates. Eyes are reduced to one to four ommatidia in all intermediates, but intermediate 3 presents up to 40 ommatidia. Ocelli are absent in intermediate 1, but present and well developed in intermediates 2 and 3. Intermediates 2 and 3 have reduced flight sclerites. The dorsum of the mesosoma is convex anteriorly and gradually slopes to the declivity in intermediate 3, but in intermediates 1 and 2 the dorsum of the mesosoma is nearly rounded anteriorly, the propodeum is below the promesonotum. The propodeum is armed with a pair of triangular teeth in all intermediates. The petiole and postpetiole do not vary much in all intermediates, the combined outline of dorsal surface of peduncle and anterior face of node is slightly concave in intermediate 1 and 2, nearly straight in intermediate 3, the petiolar node is slightly thinner in intermediate 3. Pilosity is nearly the same in all intermediates, but intermediate 3 has more abundant, short appressed hairs on the gaster. The sculpture of the head and mesosoma is almost the same in all intermediates.

Additional material examined.

MADAGASCAR: Antananarivo : Forêt de galerie, Andranorovitra, 24.0 km NNE Ankazobe, -18.11243, 47.19757, 1491 m, disturbed gallery montane forest, 2-3.vi.2008, (B.L. Fisher et al.); Antananarivo , Ankalalahana, -19.00659, 47.1122, 1375 m, Uapaca woodland, 29-31.iii.2011, (B.L. Fisher et al.); Toliara : Forêt Classée d’Analavelona, 29.4 km 343° NNW Mahaboboka, -22.675, 44.18667, 1050 m, montane rainforest, 21.ii.2003, (Fisher, Griswold et al.); Toliara , Réserve Spéciale d’Ambohijanahary, Forêt d’Ankazotsihitafototra, 35.2 km 312° NW Ambaravaranala, -18.26667, 45.40667, 1050 m, montane rainforest, 13-17.i.2003, (Fisher, Griswold et al.); Toliara , Forêt Classée d’Analavelona, 29.2 km 343° NNW Mahaboboka, -22.675, 44.19, 1100 m, montane rainforest, 18-22.ii.2003, (Fisher, Griswold et al.).