Carebara placida 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 placida Azorsa & Fisher sp. n.

Holotype.

(major worker), MADAGASCAR, Fianarantsoa , Forêt de Vevembe, 66.6 km 293° Farafangana, -22.791, 47.18183, 600 m, rainforest, transition to montane forest, 23.iv.2006, (B.L. Fisher et al.). Collection code BLF14122, (CASC: CASENT0070818). Paratypes: (1 major worker and 1 minor worker), with same data as holotype, 1 major worker (CASC: CASENT0070817) and 1 minor worker (CASC: CASENT0070818).

Diagnosis.

Antennae ten-segmented. Major: Head subrectangular, longer than wide, lateral margins slightly convex, posterior margin of head deeply concave; dorsum of propodeum flat, posterodorsal corner of propodeum angulate; head with longitudinal rugae. Minor: Head nearly subquadrate, slightly longer than wide; dorsum of promesonotum and propodeum weakly convex, posterodorsal corner convex; petiolar node roundly prominent; gaster with abundant short suberect hairs.

Description of major workers.

Measurements (n=2): HL 0.73-1.20 (0.73); HW 0.55-0.95 (0.55); SL 0.29-0.44 (0.29); ML 0.14-0.29 (0.14); EL 0.01-0.05 (0.01); EM 0.24-0.39 (0.24); HD 0.38-0.68 (0.38); WL 0.62-1.16 (0.62); PSL 0.04-0.11 (0.04); PW 0.36-0.64 (0.36); MFL 0.33-0.65 (0.33); MFW 0.09-0.15 (0.09); MTL 0.25-0.54 (0.25); PTL 0.18-0.36 (0.18); PNL 0.10-0.20 (0.10); PTH 0.14-0.25 (0.14); PTW 0.12-0.24 (0.12); PPL 0.12-0.20 (0.12); PPNL 0.12-0.18 (0.12); PPH 0.12-0.24 (0.12); PPW 0.17-0.29 (0.17); GL 0.39 -1.05 (0.39); GW 0.40-0.87 (0.40); CI 76-79 (76); MI 19-24 (19); SI 37-40 (40); MLI 60-68 (60); PPLI 56-67 (67); PPI 121-142 (142); PSI 7-12 (7).

Head slightly longer than wide (CI 76-79), in full-face view nearly subrectangular, about 1.2 times longer than wide, slightly narrowed anteriorly. Posterior margin of head deeply concave, posterolateral corners rounded, lateral margins slightly convex. Mandibles with six teeth. Anterior margin of clypeus slightly concave in the middle, nearly straight, and laterally convex. Ocelli present or absent. Antennae with ten segments. Scapes short (HL 0.73-1.20, SL 0.29-0.44, SI 37-40). Eyes present, consisting of fifteen to thirty ommatidia (EL 0.01-0.05). Supraclypeal area acutely triangular and well defined.

In profile view, posterolateral corner of head with a small triangular tooth resembling a horn. Promesonotum convex, (metanotum present in larger major workers), dorsum of mesonotum slightly convex, promesonotal suture present on dorsum, metanotal groove deeply impressed, propodeum lower than promesonotum, and about 1.6 times higher than long, dorsal face of propodeum slightly convex, nearly flat, and declining posteriorly; posterodorsal corners of propodeum angulate (more noticeable in larger major workers); anterodorsal corner nearly rounded; declivity concave with thin lateral laminae. Propodeal lobes convex. Propodeal spiracle rounded and situated above mid-height of sclerite, and beyond mid-length of sclerite by about two times the diameter of the spiracle, (closer to mid-length and mid-height in larger major workers), distance from propodeal spiracle to posterodorsal corner of propodeum about twice the diameter of the spiracle (PSL 0.04-0.11), and distance to declivity less than half the diameter of the spiracle. In dorsal view, promesonotum about as long as wide, anterior margin and sides rounded, sides weakly convex in larger major workers; sides of propodeum convex, and straight in larger major workers.

Petiole longer than high (PTL 0.18-0.36, PTH 0.14-0.25) and with relatively long peduncle, ventral face slightly convex, nearly flat. Combined outline of dorsal surface of peduncle and anterior face of node medially concave, posterior face of node convex, anterodorsal and posterodorsal corner convex, dorsum rounded. Subpetiolar process produced as denticle, barely larger than the diameter of the propodeal spiracle. Postpetiolar node nearly rounded and slightly lower than petiolar node. In dorsal view, postpetiolar node slightly wider than petiolar node (PTW 0.12-0.24, PPW 0.17-0.29) and petiolar node wider than long (PNL 0.10-0.20, PTW 012-0.24), anterior margin of petiole convex, posterior margin straight, anterior and posterior margin of postpetiole straight, sides nearly rounded in petiole and postpetiole.

Dorsal surface of mandibles, clypeus and supraclypeal area smooth and shiny with scattered piligerous punctae on head and mandibles. Head with longitudinal rugae directed to the posterior margin, gena with well-developed and longitudinal rugae. Posterolateral portion of cephalic dorsum with longitudinal rugae, smooth and shiny on larger major workers. Mesosoma smooth and shiny, except for katepisternum and sides of propodeum (areolate) and metapleuron (finely areolate and with longitudinal rugae). Petiole and ventral face of postpetiole finely areolate. In dorsal view, mesosoma, petiole, postpetiole and gaster smooth and shiny.

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

Description of minor workers.

Measurements (n=2): HL 0.40-0.41; HW 0.38; SL 0.26-0.27; ML 0.10-0.13; EL 0.01; EM 0.13; HD 0.25; WL 0.45-0.47; PSL 0.02-0.03; PW 0.22-0.24; MFL 0.26; MFW 0.07-0.08; MTL 0.21; PTL 0.13-0.14; PNL 0.08-0.09; PTH 0.11; PTW 0.08-0.09; PPL 0.09; PPNL 0.09; PPH 0.09; PPW 0.12-0.13; GL 0.32-0.34, GW 0.30-0.33; CI 93-95; MI 24-33; SI 65-66; MLI 68; PPLI 64-69; PPI 133-163; PSI 5-8.

Head slightly longer than wide (CI 93-95), in full-face view nearly subquadrate, about 1.1 times longer than wide. Posterior margin of head straight, posterolateral corners rounded, lateral margins weakly convex. Mandibles with five teeth. Anterior margin of clypeus nearly straight, and laterally angulate. Antennae with ten segments. Scape fails to reach the posterior margin of head (HL 0.40-0.41, SL 0.26-0.27, SI 65-66). Eyes present, consisting of one ommatidium (EL 0.01). Supraclypeal area triangular but poorly defined.

In profile, promesonotum weakly convex, nearly straight, metanotal groove deeply impressed. Propodeum about 1.2 times higher than long, dorsal face of propodeum weakly convex, declining posteriorly, posterodorsal corner unarmed (nearly convex), declivity slightly concave, nearly flat, with thin lateral laminae. Propodeal lobes convex. Propodeal spiracle rounded and situated above mid-height of sclerite, and beyond mid-length of sclerite by about two times the diameter of the spiracle, distance from propodeal spiracle to posterodorsal corner of propodeum and distance to declivity same as the diameter of the spiracle (PSL 0.02-0.03). In dorsal view, promesonotum slightly longer than wide, anterior margin rounded, sides convex, narrowed posteriorly; sides of propodeum convex.

Petiole longer than high (PTL 0.13-0.14, PTH 0.11) and with relatively short peduncle, ventral face medially convex. Petiolar node thick, combined outline of dorsal surface of node and anterior face of node medially concave, posterior margin slightly convex, anterodorsal corner convex and posterodorsal corner rounded, dorsum nearly rounded. Subpetiolar process produced as a small denticle, almost the same as the diameter of the propodeal spiracle. Postpetiolar node strongly convex and lower than petiolar node. In dorsal view, postpetiolar node wider than petiolar node (PTW 0.08-0.09, PPW 0.12-0.13), and petiolar node as wide as long (PNL 0.08-0.09, PTW 0.08-0.09), anterior margin of petiole convex, posterior margin nearly straight, anterior and posterior margins of postpetiole straight, sides convex 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 katepisternum and metapleuron which are finely areolate. Petiole and ventral face of postpetiole finely areolate. In dorsal view, mesosoma, petiole, postpetiole and gaster smooth and shiny.

Lateral margins, posterior margin of head, scape and outer margin of mandible with suberect to subdecumbent hairs. Mesosoma with erect to suberect hairs. Petiole and postpetiole with short and long subdecumbent hairs. Tibia with decumbent hairs. Gaster with abundant suberect hairs. Color yellowish.

Distribution and biology.

Carebara placida is known only from one locality in southeastern Madagascar (Figure 69). Individuals of this species occur in rainforest and transition to montane forest at an elevation of 600 m, and were collected under stones.

Comments.

Carebara placida can be separated from other species by the next combination of characters: dorsum of head with well-defined longitudinal rugae, while others species are either unsculptured or with irregular longitudinal rugae. C. placida is known only from one locality in southeastern Madagascar. Other six species were recorded at the same locality: C. dota , C. grandidieri , C. hainteny , C. hiragasy , C. jajoby , and C. nosindambo .

C. placida have two intermediates in the major worker subcaste (Figure 58). The posterolateral corner of head in intermediates slightly narrowed posteriorly. The posterior margin of the head is weakly to deeply concave in both intermediates. Eyes are small and reduced to one ommatidium in intermediate 1, and with 14 ommatidia in intermediate 2. Ocelli are absent in intermediate 1, but present and well developed in intermediate 2 (one ocellus). Reduced flight sclerites are present in intermediate 2. The dorsum of the promesonotum is high and nearly rounded in intermediate 1, and nearly convex in intermediate 2. The combined outline of dorsal surface of peduncle and anterior face of node medially concave in intermediate 2, and slightly concave, nearly straight in intermediate 1. The sculpture of the head in both intermediates is the same. The pilosity on the head, mesosoma, petiole and postpetiole is the same in both intermediates. The pilosity on the gaster of intermediate 1 is composed of short subdecumbent hairs and sparse, long suberect hairs, while intermediate 2 has very short decumbent to appressed hairs and sparse, long suberect hairs.