Stigmatomma crypticum

The holotype and paratypes belong to a single polygynous colony probably at an early stage of colony development (because only a few workers were present). The colony nested underground (in soil) in “Sang Le Forest” dominated by Lagerstroemia tomentosa C. Presl, 1844 (family Lythraceae).

Identification
Eguchi et al. (2015) - Most similar to Stigmatomma caliginosum, Stigmatomma fulvidum, Stigmatomma pertinax and Stigmatomma zwaluwenburgi.

The worker and queen of S. caliginosum is easily distinguished from those of Stigmatomma crypticum by: (1) anteromedian portion of clypeus lacking a pair of extremely long and flexible setae; (2) frontal carinae inconspicuous, extending by no more than the length of frontal lobe; (3) posterolateral part of propodeum feebly produced posteriad. Furthermore, the worker of S. caliginosum is distinguished from that of S. crypticum by the 9th and 10th antennal segments each (a little) shorter than long.

The worker of S. fulvidum is easily distinguished from those of Stigmatomma crypticum by: (1) antenna 10- segmented; (2) frontal carinae inconspicuous, extending by no more than the length of frontal lobe; (3) posterolateral part of propodeum feebly produced posteriad.

The worker of S. pertinax is easily distinguished from that of Stigmatomma crypticum by: (1) head a little broader than long (CI=101.9, according to the original description); (2) apical blade of mandible shorter and broader; (3) preapical denticle of apical blade of mandible developed well; (4) mid-basal tooth row of mandible consisting of 5 teeth of which basal four small and obliquely truncate apically, almost equal in size; (5) frontal carinae inconspicuous, extending by no more than the length of frontal lobe; (6) posterolateral part of propodeum feebly produced posteriad; (7) subpetiolar process large and lobate, but not spatulate.

The worker of S. zwaluwenburgi is easily distinguished from that of Stigmatomma crypticum by: (1) frontal carinae inconspicuous, extending by no more than the length of frontal lobe; (2) antennal segments VIII–X each shorter than long; (3) posterolateral part of propodeum feebly produced posteriad.

Distribution based on Regional Taxon Lists
Oriental Region: Vietnam.

Nomenclature

 *  crypticum. Bannapone cryptica Eguchi, Bui, Yamane & Terayama, 2015: 79, figs. 1-11 (w.q.) VIETNAM. Combination in Stigmatomma: Ward & Fisher, 2016: 691.

Worker
Holotype: HL 0.786 mm; HW 0.645 mm; MBL 0.565 mm; SL 0.358 mm; ML 0.889 mm; PNW 0.416 mm; HFL 0.429 mm; PL 0.314 mm; PW 0.292 mm; A3W 0.411 mm; A4W 0.527 mm; CI 82; MBI 88; SI 56; MI 214; HFI 67; A3I 141; A4I 128.

Paratypes (n=2) and nontypes (n=2): HL 0.711–0.786 mm; HW 0.581–0.640 mm; MBL 0.516–0.562 mm; SL 0.326–0.360 mm; ML 0.815–0.890 mm; PNW 0.370–0.409 mm; HFL 0.381– 0.424 mm; PL 0.297–0.317 mm; PW 0.266–0.293 mm; A3W 0.383–0.415 mm; A4W 0.475–0.520 mm; CI 81–83; MBI 88–91; SI 56–58; MI 213–228; HFI 66; A3I 138–144; A4I 124–126.

Body relatively densely covered with short suberect to decumbent hairs. Median furrow present only in posteriormost part of vertex; frontal lobes closely approximate to each other; frontal carinae conspicuous, reaching vertex, weakly divergent posteriad from the end of frontal lobe, then becoming almost parallel, and finally divergent strongly; antennal scrobe moderately impressed, running along frontal carina; anterior margin of clypeus slightly convex, with 7 peg-like setae, each being based on short tubercle; sets of setae and tubercles decreasing in size laterad (mesal five conspicuous, but lateralmost often reduced); anteromedian portion of clypeus bearing a pair of extremely long and flexible setae; apical blade of mandible with a small preapical denticle; mid-basal tooth row of mandible consisting of 4 blunt teeth which decrease in size toward the base; 1st and 2nd extremely elongated trapezoidal; 3rd and 4th trapezoidal; antennal scape weakly bent near its apex; funiculus incrassate apically but not forming a distinct club; 9th and 10th antennal segments each a little longer than broad; posterolateral part of propodeum stongly produced posteriad; metapleural gland bulla, when seen through the sclerite, large and bean-shaped; petiole in lateral view with anterior face almost as long as or a little longer than dorsal face in lateral view; the two faces meeting at a blunt angle; subpetiolar process spatulate and weakly curved, produced anteroventrad, without translucent fenestra; abdominal segment III shorter and narrower than IV; girdling constriction between abdominal segments III and IV weak. Dorsum of head distinctly rugoso-reticulate; mandible distinctly rugose longitudinally; anterior and anterolateral part of pronotum faintly reticulate; remainder part of mesosoma nearly smooth except for hair pits; dorsal and lateral face of petiole and gaster and legs smooth with hair pits.

Queen
Measurements and indices of the paratypes (n=2): HL 0.757–0.765 mm; HW 0.621–0.637 mm; MBL 0.567 mm; SL 0.356–0.361 mm; ML 1.032–1.071 mm; PNW 0.454–0.469 mm; HFL 0.420–0.431 mm; PL 0.350–0.371 mm; PW 0.327–0.336 mm; A3W 0.464–0.479 mm; A4W 0.582–0.604 mm; CI 82–83; MBI 89–91; SI 57; MI 227– 228; HFI 68; A3I 142–143; A4I 125–126.

(Vietnamese material only). The queen similar to the worker except for the following features: with head in full-face view median ocellus located at level of posterior margin of compound eye; distance between median ocellus to lateral ocellus shorter than that between lateral ocelli; mesopleuron partly subdivided into anepisternum and katepisternum with a faint sulcus (Fig. 9); pronotum and propodeum moderately reticulate; mesoscutum moderately rugose longitudinally; mesoscutellum nearly smooth with hair pits; mesopleuron weakly rugoso-reticulate; dorsal and lateral face of petiole weakly reticulate.

Type Material
Holotype: worker [voucher: IMG20150208-1;, Vietnam: Nghe An: Tuong Duong: “Sang Le Forest”, < ca. 220 m alt., K. Eguchi leg., 02/iv/2006 [colony: Eg02iv06-19]. Paratypes: 2 workers, 2 dealate queens from the same colony as holotype.

Determination Clarifications
Stigmatomma sp. eg-3 in Eguchi (2014)