Myopias bidens

Myopias bidens (Emery, 1900)

(Figs. 13–15)

Trapeziopelta bidens Emery, 1900: 313 (diagnosis in key). Holotype worker, INDONESIA, Sumatra, Si-Rambé (MSNG, AntWeb image examined).

Myopias bidens: Bolton, 1995: 269 (combination in Myopias); Xu et al. 2014: 166 (diagnosis in key): Probst et al. 2015: 204 (diagnosis in key).

Non-types. THAILAND: Six workers, Tak Prov., Um Phang Dist., Mae Khlong Yai Village, Um Phang W.S., Old Field, 950–1000 m a.s.l., 11.IX.2004, W. Jaitrong leg., Colony no. WJT04-W-002 (THNHM); 19 workers, Tak Prov., Um Phang Dist., Thung Yai Naresuan East W.S., Ka-Ngae Sod Forest Ranger Station, 20.II.2015, W. Jaitrong leg., Colony no. TH15-WJT-405 (THNHM); 13 workers, Tak Prov., Um Phang Dist., Thung Yai Naresuan East W.S., Huai Nam Kheao Forest Ranger Station, 23.VI.2015, W. Jaitrong leg., Colony no. TH15-WJT-923 (AMK, NMNH, THNHM); 10 workers, Tak Prov., Um Phang Dist., Thung Yai Naresuan East W.S., Thung Nanoi Forest Ranger Station, 22.III.2016, W. Jaitrong leg., Colony no. TH16-WJT-0184 (THNHM); 36 workers, Tak Prov., Um Phang Dist., Thung Yai Naresuan East W.S., Thung Nanoi Forest Ranger Station, Swamp forest, 23.III.2016, W. Jaitrong leg., Colony no. TH16-WJT-0 184 (AMK, NMNH, THNHM); 11 workers, Tak Prov., Um Phang Dist., Thung Yai Naresuan East W.S., Thung Nanoi Forest Ranger Station, Swamp forest, 23.III.2016, W. Jaitrong leg., Colony no. TH16-WJT-0202 (AMK, THNHM); 27 workers, Tak Prov., Um Phang Dist., Thung Yai Naresuan East W.S., Head Quarter, 15.32472222°N, 98.91527778°E, 820 m a.s.l., 22. II.2016, W. Jaitrong leg., TH16-WJT-0001 (THNHM); 1 worker, Chanthaburi Prov., Khlung Dist., near Trok Nong Waterfall, 12.54250000°N, 102.23694444°E. 155 m a.s.l., 24.XI.2003, W. Jaitrong leg. (THNHM); 1 worker, Chanthaburi Prov., Soi Dao Dist., 13.10277778°N, 102.19388889°E, 300 m a.s.l., 19.I.2008, W. Jaitrong leg. (THNHM); 1 worker, Narathiwat Prov., Su Ngai Ko Lok Dist., Ban Tao Dang, 6.07277778°N, 101.96500000°E, 12 m a.s.l., 12.X.2000, A. Suwannasri leg. (THNHM).

Measurements. Non-type workers (n = 15): TL 5.10–5.50, HL 0.96–1.06, HW 0.79–0.96, SL 0.69–0.86, ED 0.10–0.13, ML 0.66–0.76, PW 0.56–0.63, MSL 1.39–1.52, PL 0.36–0.46, PH 0.46–0.53, DPW 0.40–0.43. CI 83– 91, SI 88–90, OI 12–15, MI 69–72, LPI 114–127, DPI 100–109.

Diagnosis of worker: Body 5.10–5.50 mm in total length (small size). Masticatory margin of mandibles with four teeth (fig. 5); median clypeal lobe about as long as broad, squared, its anterior margin distinctly concave; eyes relatively small with 5–6 ommatidia along the longest axis; antennal scape relatively short, not reaching posterior margin of head; petiole in profile subrectangular, almost as long as high; subpetiolar process subtriangular, located anteroventrally, its apex truncate and pointed downward. Entire body (head, mandible, antennal scape, mesosoma, legs, and metasoma) smooth and shiny except for lower portion of lateral face of propodeum finely striate. Body entirely reddish brown to yellowish brown, head darker than elsewhere.

Habitat. Myopias bidens is distributed from lowland to highland in various types of forests (swamp forest, evergreen forest, dry evergreen forest and hill evergreen forest) and within both primary and secondary forests. All colonies of M. bidens were large, with up to a thousand workers, and nesting in rotten wood in an advanced stage of decomposition.

Distribution. Thailand (Tak, Chanthaburi and Narathiwat Provinces, new record, fig. 52) and Indonesia (Sumatra) (Probst et al. 2015).

Comparative notes. Myopias bidens is similar in general appearance to M. breviloba, M. castaneicola, M. mayri, and M. trumani in having the following characteristics in the worker: masticatory margin of mandibles with conspicuously produced basal angle followed by a distinct concavity; masticatory margin blade between basal angle and prebasal tooth subequal in length to distance between prebasal tooth and apical tooth; median clypeal lobe with concave anterior margin, anterolateral corners conspicuously dentate; head smooth and shiny. However, this species is most similar to M. breviloba in having large compound eyes, with maximum diameter being longer than malar space length (eyes reduced, with maximum diameter being shorter than malar space length in M. castaneicola, M. mayri and M. trumani). It is separated from M. breviloba by the condition of the median clypeal lobe that has the median lobe length subequal to its width, while the medial lobe is clearly shorter than wide in M. breviloba; body colour is reddish brown to dark brown in M. bidens, while body colour is paler in M. breviloba.