Crematogaster quadriruga

This species inhabits disturbed to developed forests and nests in dead twigs on trees.

Identification
Hosoishi and Ogata (2016) - A member of the Crematogaster quadriruga group. In the worker this species can be distinguished from all other members of the C. quadriruga group by the distinct compound eyes, propodeal spiracles small and apart from metapleural gland bulla, and petiole with subparallel sides in dorsal view. This species is similar to Crematogaster suehiro, but can be distinguished from it by longitudinal rugulae on clypeus not extending to posterior clypeal margin, bicolored body, petiole with subparallel sides in dorsal view.

Specimens from northern part of Thailand (Chiang Mai) differ from other specimens in having the developed rugulae on promesonotum, slightly large propodeal spiracles and slightly broader petiole with sculptured surface. Single specimen from Laos has erect longer setae on pronotal shoulders medially. Some specimens from Bokor National Park, Cambodia differ in having yellow-colored gaster.

Distribution
Laos, Cambodia, Thailand, and Indonesia (N. Sumatra).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Indonesia. Oriental Region: Cambodia, Laos, Thailand.

Nomenclature

 *  quadriruga. Crematogaster biroi var. quadriruga Forel, 1911h: 455 (w.) THAILAND. Combination in C. (Orthocrema): Emery, 1922e: 132. Status as species: Hosoishi & Ogata, 2016: 594.

Worker
Hosoishi and Ogata (2016) - (n=8) HW 0.46–0.50; HL 0.48–0.51; CI 94–100; SL 0.44–0.48; SI 94–100; EL 0.11–0.12; PW 0.27–0.31; WL 0.54–0.60; PSL 0.11–0.13; PtL 0.17–0.22; PtW 0.14–0.17; PtH 0.13–0.15; PpL 0.12–0.17; PpW 0.15–0.18; PtHI 68–79; PtWI 74–85; PpWI 100–145; WI 100–113.

Workers monomorphic, but intermediate worker as large as queen. Head subquadratic in full-face view. Mandibles with four teeth arranged at an equal distance, apical and subapical teeth large, basal two teeth smaller. Anterior clypeal margin convex in medial portion. Compound eyes distinctly projecting beyond lateral margins of head in full-face view. Scapes reaching posterolateral corners of head.

Pronotal collar with weakly concave anterior margin in dorsal view, distinctly lower than pronotum in lateral view. Pronotal dorsum with ridges laterally. Mesonotal dorsum with lateral ridges that irregularly extend posteriad to tips of propodeal spines. Pronotum and mesonotum in lateral view not clearly forming continuous dorsal outline; mesonotal dorsum higher anteriorly. Metanotal groove in dorsal view transverse, almost straight in median portion, forming deep concavity that is laterally margined by lamellate ridges. Propodeal spiracles oval, situated at posterolateral corners of propodeum, apart from metapleural gland bullae. Propodeal spines developed, longer than diameter of propodeal spiracles, in dorsal view directed posteriad.

Petiole in dorsal view with subparallel sides and narrow anteriorly, longer than wide. Posterior portion of petiole with short process that is slightly higher than posterior margin of petiole disc in lateral view. Subpetiolar process developed as acute process. Postpetiole in lateral view with weakly convex dorsum, as high as petiole, in dorsal view as wide as petiole, weakly bilobed posteriorly but without longitudinal sulcus. Subpostpetiolar process undeveloped, but venter of postpetiole convex.

Integument essentially smooth and shining. Dorsal surface of head smooth and shining. Mandibles with feeble rugulae and smooth interspaces. Clypeus generally smooth and shining, but with one distinct pair of longitudinal longer rugulae and one pair of shorter rugulae laterally; longer rugulae not extending to posterior clypeal margin. Dorsal and lateral surfaces of pronotum smooth and shining; anterolateral shoulders of pronotum with longitudinal rugulae. Mesopleura weakly punctuate, but seems smooth and shining. Dorsal surface of propodeum generally smooth and shining, but with longitudinal rugulae anteriorly. Dorsal and lateral surfaces of petiole smooth and shining. Dorsal and lateral surfaces of postpetiole smooth and shining.

Standing pilosity sparse. Dorsal face of head with erect setae sparsely. Clypeus with two pairs of long setae in anterior portion, one directed upward and the other downward. Anterior clypeal margin with one pair of long setae medially and short setae laterally. Scapes with suberect and decumbent setae. Mesosoma with five to six pairs of long erect and stout setae (ps1PN, psaMN, pspMN, ps1PS, and one to two ps2PS) that are much longer than other erect setae. Posterolateral tubercles of petiole posteriorly with one pair of stout long setae and one pair of short setae laterally. Postpetiole with three pairs of setae on disc anterodorsally, anterolaterally and posteriorly. Fourth abdominal tergite with erect setae abundantly, and short appressed setae sparsely.

Body bicolored with head, mesosoma, petiole, postpetiole and first gaster yellow and with the remains of the gaster brown. All flagellar segments yellow.

Intermediate. (n=2) HW 0.65–0.68; HL 0.66–0.68; CI 98–100; SL 0.60–0.61; SI 90–92; EL 0.17; PW 0.48–0.51; WL 0.89–0.92; PSL 0.15; PtL 0.35; PtW 0.25–0.26; PtH 0.23–0.25; PpL 0.21–0.22; PpW 0.28–0.29; PtHI 66–71; PtWI 71–74; PpWI 131–133; WI 111–112.

With worker character conditions, except as follows.

Three ocelli present.

Mesonotum strongly convex in lateral view. Posterior face of mesonotum steeply sloping so that in lateral view dorsal outline of promesonotum not smoothly arched.

Subpetiolar process developed as blunt process.

Dorsal surface of pronotum generally smooth, but with feeble rugulae. Dorsal surface of propodeum weakly punctuated with longitudinal rugulae. Lateral surface of petiole weakly sculptured. Dorsal surface of postpetiole smooth and shining.

Posterolateral tubercles of petiole with three to four pairs of stout long setae posteriorly. Fourth abdominal tergite with erect setae abundantly, and short appressed setae sparsely.

Body usually bicolored with head, mesosoma, petiole, postpetiole and first gater yellow and with remains of gaster brown to black.

Type Material
Hosoishi and Ogata (2016) - Syntype workers, Kerr, Thailand (M. Waldo) (, examined). One syntype worker (top specimen of three on one pin) in MHNG here designated Lectotype.

References based on Global Ant Biodiversity Informatics

 * Hosoichi S., and K. Ogata. 2016. Systematics and biogeography of the ant genus Crematogaster Lund subgenus Orthocrema Santschi in Asia (Hymenoptera: Formicidae). Zoological Journal of the Linnean Society 176: 547–606.
 * Jaitrong W., B. Guenard, E. P. Economo, N. Buddhakala, and S. Yamane. 2016. A checklist of known ant species of Laos (Hymenoptera: Formicidae). Asian Myrmecology 8: 1-32. DOI: 10.20362/am.008019
 * Leong C. M., S. F. Shiao, and B. Guenard. 2017. Ants in the city, a preliminary checklist of Formicidae (Hymenoptera) in Macau, one of the most heavily urbanized regions of the world. Asian Myrmecology 9: e009014.