Crematogaster vacca

Identification
A member of the subgenus Physocrema. This species is easily distinguished from Crematogaster difformis and its subspecies by the well developed propodeal spines.

Key to Crematogaster Physocrema species

Distribution
Known from Malay Peninsula and Borneo.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Indonesia, Malaysia.

Nomenclature

 *  vacca. Crematogaster deformis subsp. vacca Forel, 1911d: 384 (w.) WEST MALAYSIA. Raised to species and senior synonym of detritinodis, stethogompha: Hosoishi & Ogata, 2009b: 30.
 * detritinodis. Crematogaster (Physocrema) stethogompha var. detritinodis Wheeler, W.M. 1919e: 77 (w.) BORNEO. Junior synonym of vacca: Hosoishi & Ogata, 2009b: 30.
 * stethogompha. Crematogaster (Physocrema) stethogompha Wheeler, W.M. 1919e: 75 (w.) BORNEO. Junior synonym of vacca: Hosoishi & Ogata, 2009b: 30.

Worker
Hosoishi and Ogata (2014) - HW 1.09–1.62; HL 1.03–1.46; CI 106–111; SL 0.91–1.14; SI 70–83; EL 0.20–0.26; PW 0.64–0.84; WL 1.32–1.76; PSL 0.16–0.18; PtL 0.41–0.54; PtW 0.37–0.42; PtH 0.23–0.30; PpL 0.23–0.30; PpW 0.30–0.42; PtHI 56–57; PtWI 78–90; PpWI 129–140; WI 81–100 (Three workers measured).

Workers with pronounced size polymorphism.

Scape not reaching posterior corner of head in large workers.

In lateral view, pronotum and mesonotum forming a single convexity; propodeum distinctly raised relative to promesonotum. Anterior margin of pronotal collar slightly concave in dorsal view. Metanotal groove convex posteriorly in dorsal view, deep and situated posteriorly to the posterior ridge of pronotum in lateral view; thorax not strongly constricted in middle in dorsal view. In dorsal view, many longitudinal rugulae connecting between mesonotum and propodeum; but the boundary distinct. Propodeal spiracle situated away from the metapleural gland orifice, the distance between them much greater than the propodeal spiracle diameter. Propodeal spines present.

Postpetiole slightly bilobed behind without longitudinal median sulcus.

Clypeus sculptured with longitudinal rugulae. Reticulate rugulae on dorsal face of head, pronotum, mesonotum and propodeum.

Standing pilosity sparse on dorsal face of head and mesosoma. Dorsal face of head with appressed setae.

Fourth abdominal tergite with a few erect setae and abundant appressed setae.

Body color dark brown to black.

Type Material
Hosoishi and Ogata (2014) - LECTOTYPE worker (by present designation) from MALAYSIA: Berhentian Tingi, Nigri Sembilan, Malacca (R. Martin) [examined]. The name on the labels of the type specimen,“ Crematogaster stethogompha laevinodis” does not correspond to the name “Crematogaster stethogompha detritinodis” used in Wheeler’s description. He presumably changed the name between the time the labels were prepared and the manuscript submitted.