Crematogaster monocula

This species is known from two workers collected from a lowland forest by Winkler extraction of leaf litter. It is only known from the type locality in Cambodia.

Identification
Crematogaster monocula is a member of the C. biroi group of the subgenus Orthocrema and shares all the group-specific characters (HOSOISHI & OGATA 2016). This species is well distinguished from all other Asian species of this species group by having one ommatidium and a relatively short scape (SI 64–66). Crematogaster monocula is similar to Crematogaster masukoi, but can be distinguished by having only one ommatidium, almost straight anterior clypeal margin and sculptured petiole.

Distribution based on Regional Taxon Lists
Oriental Region: Cambodia.

Nomenclature

 * . Crematogaster monocula Hosoishi, 2019: 508, figs. 1-7 (w.) CAMBODIA.
 * Type-material: holotype worker, 1 paratype worker.
 * Type-locality: holotype Cambodia: Koh Kong, 141 m., 11°31’N, 103°09’E, 19.v.2012 (S. Hosoishi); paratype with same data but 18.v.2012.
 * Type-depositories: TNHM (holotype); KUEC (paratype).
 * Distribution: Cambodia.

Worker
HW: 0.42 / 0.41; HL: 0.43 / 0.42; CI: 98 / 97; SL: 0.27 / 0.27; SI: 64 / 66; EL: 0.02 / 0.02; PW: 0.27 / 0.28; WL: 0.53 / 0.52; PSL: 0.04 / 0.03; PtL: 0.14 / 0.13; PtW: 0.16 / 0.16; PtH: 0.11 / 0.11; PpL: 0.12 / 0.11; PpW: 0.16 / 0.16; PtHI: 79 / 85; PtWI: 114 / 123; PpWI: 133 / 145; WI: 100 / 100.

Workers monomorphic.

Head subquadrate in full-face view. Mandible with four teeth, basal tooth arranged away from third apical one; mandibular dentition worn-out and blunt in type specimens. Anterior clypeal margin almost straight in medial portion. Compound eye consisting of one ommatidium, not projecting beyond lateral margins of head in full-face view. Antenna 11-segmented. Antennal club 2-segmented. Scape not reaching posterolateral corners of head.

Pronotal collar with almost straight anterior margin in dorsal view, distinctly lower than pronotal dorsum in lateral view. Pronotal dorsum without distinct ridges laterally in dorsolateral view. Mesonotal dorsum without lateral ridges. Pronotum and mesonotum in lateral view forming slightly convex, continuous dorsal outline. Metanotal groove in dorsal view transverse, almost straight in median portion, forming deep concavity that is laterally margined by thin lamellate ridges. Propodeal spiracle oval, situated at posterolateral corners of propodeum, touching metapleural gland bullae. Propodeal spine shorter than maximum diameter of propodeal spiracle, in dorsal view directed posteriorly.

Petiole in dorsal view with weakly convex sides and narrowed anteriorly, longer than broad. Posterior portion of petiole without distinct process in lateral view. Subpetiolar process developed, acute apically. Postpetiole in lateral view with dorsum weakly convex and as high as petiole, in dorsal view as wide as petiole, weakly bilobed posteriorly, but without longitudinal sulcus. Subpostpetiolar process developed as small process.

Integument weakly sculptured. Dorsal surface of head generally smooth, but with rugulae on region surrounding antennal sockets. Mandibles smooth. Clypeus smooth and shining without distinct longitudinal rugulae. Dorsal and lateral surfaces of pronotum smooth and shining; anterolateral shoulders of pronotum without rugulae. Mesopleuron weakly sculptured. Longitudinal rugulae on higher portion of mesopleuron developed. One pair of rugulae running from metanotal groove extending posteriorly and diverging to propodeal spines in dorsal view. Dorsal surface of propodeum with feeble rugulae. Lateral surface of propodeum mostly smooth and shining, but weakly sculptured with rugulae on anterior areas. Dorsal surface of petiole generally smooth. Lateral surface of petiole sculptured. Dorsal surface of postpetiole smooth and shining. Lateral surface of postpetiole smooth.

Standing pilosity sparse. Dorsal face of head with sparse erect and stout setae. Clypeus with two pairs of long and stout setae in anterior portion, one directed upward and the other downward. Anterior clypeal margin with one pair of long setae (0.15 mm) medially, and a few pairs of short setae laterally. Scape with sparse erect to suberect setae. Mesosoma with four pairs of long erect and stout setae on pronotal shoulders, anterior and posterior mesonotal ridges, near base of propodeal spines that are much longer than other erect setae. Posterolateral tubercles of petiole posteriorly with three pairs of long and stout setae. Postpetiole with two pairs of long and stout setae on disc anterolaterally, posteriorly. Fourth abdominal tergite with sparse erect setae, no decumbent to appressed setae.

Body yellow. All flagellar segments yellow.

Etymology
The species name refers to one ommatidium (ʻmono’ and ʻoculus’ are Latin words for ʻone’ and ʻeye’, respectively). Noun in apposition.

References based on Global Ant Biodiversity Informatics

 * Hosoichi S. 2019. A new subterranean Crematogaster with one ommatidium from Cambodia, based on morphology and DNA (Hymenoptera: Formicidae). Acta Entomologica Musei Nationalis Pragae 59(2): 507-511.