Crematogaster yaharai

Worker specimens of this species were collected from a disturbed community forest in Kampong Chhnang Province, Cambodia. It is only known from the type locality.

Identification
Hosoishi and Ogata (2019) - A member of the Crematogaster rothneyi group. This species is very similar to Crematogaster rothneyi, but can be distinguished by the longer than broad antennal segments V and VI, smooth mesopleuron and smooth or weakly punctuated propodeum (see photo below in caste section).

Distribution based on Regional Taxon Lists
Oriental Region: Cambodia.

Biology
Hosoishi and Ogata (2019) - These Cambodian specimens (Crematogaster yaharai) were distantly related to the western and eastern populations, as shown by 12S and a COI sequence divergence. This deep genetic gap indicates that Cambodian populations have been genetically isolated from other Crematogaster rothneyi populations for a very long time. Crematogaster rothneyi is widely distributed in South and Southeast Asia, and this sister species, Crematogaster yaharai, is completely within its distribution range. The lowland forest collection locality is not a geographically isolated area, such as high mountains.

Nomenclature

 *  yaharai. Crematogaster yaharai Hosoishi & Ogata, 2019: 9, figs. 4, 5B (w.) CAMBODIA.

Worker
Holotype: HW 0.78; HL 0.77; CI 101; SL 0.76; SI 97; EL 0.2; PW 0.48; WL 0.89; PSL 0.11; PtL 0.26; PtW 0.33; PtH 0.17; PpL 0.2; PpW 0.33; PtHI 65; PtWI 127; PpWI 165; WI 100. Paratype: HW 0.63-0.76; HL 0.63-0.75; CI 99-101; SL 0.68-0.81; SI 104-115; EL 0.18-0.24; PW 0.41-0.48; WL 0.71-0.88; PSL 0.08-0.11; PtL 0.23-0.28; PtW 0.27-0.33; PtH 0.15- 0.19; PpL 0.16-0.21; PpW 0.28-0.34; PtHI 64-70; PtWI 104-122; PpWI 148-175; WI 97-115 (Four paratype workers measured).

Polymorphic workers with moderate size variation.

Head subquadrate in full-face view, with weakly concave posterior margin, angular posterior corners and convex sides. Occipital carinae developed. Mandible with four teeth, apical and subapical teeth large. Anterior margin of clypeus convex with slightly impressed median portion; anterolateral margins of clypeus protruded anteriorly; posterior margin of clypeus rounded between frontal lobes. Frontal carinae almost parallel. Antennae 11 segmented; relative scape length variable with worker size (SI, 97-115); SI lower in larger specimens; antennal club 3-segmented. Scape exceeding posterior corner of head by 1/4 of its length or more. Antennal segments V and VI each 1.5 times longer than broad. Compound eyes distinctly projecting beyond lateral margins of head in full-face view, especially in large workers. Pronotum and mesonotum fully fused without defined suture. In lateral view, posterior half of dorsolateral margin of mesonotum forming triangle shaped process, anterior half forming almost flat outline. Mesothoracic spiracle reduced to form small pit dorsoventrally. Metapleural gland opening slit-shaped. Propodeal spiracle elliptical, situated at posterolateral corner, apart from metapleural gland bulla. Metanotal groove straight in dorsal view, deep and forming concave region between mesonotum and propodeum. In dorsal view, longitudinal rugulae not connecting between mesonotum and propodeum. Propodeal spines short. Petiole scoop-shaped, broader anteriorly, longer than broad in dorsal view; spiracle situated at midportion between dorsal and ventral margin of petiole in lateral view, directed lateroposteriorly. Postpetiole with distinct longitudinal median sulcus, bilobed in dorsal view; spiracle situated anteriorly on lateral surface in lateral view. Dorsum of head weakly sculptured with longitudinal rugulae. Clypeus with longitudinal rugulae in large workers, but weakly punctuated in small workers. Promesonotum punctuated. Central region of mesopleuron smooth, but higher anterior and lower posterior regions weakly sculptured. Dorsal surface of propodeum smooth or weakly punctuated. Lateral surface of propodeum smooth and shining. Dorsal and lateral surface of petiole sculptured. Dorsal and lateral surface of postpetiole sculptured. Median sulcus of postpetiole smooth. Standing pilosity sparse. Dorsum of head with short and erect setae. Clypeus with some pairs of erect setae. Anterior clypeal margin with one pair of long setae mixed with short setae laterally. Mesonotal dorsum with sparse erect setae. Petiole with suberect setae. Postpetiole with suberect setae. Fourth abdominal tergite with sparse erect setae. Body color: Yellow-brown.

Etymology
The specific name is dedicated to Japanese biologist Dr. Tetsukazu Yahara, who helped our field surveys in Cambodia.