Myopias mandibularis (Crawley, 1924)

Jaitrong, Weeyawat, Tasen, Wattanachai & Guénard, Benoit, 2018, The ant genus Myopias Roger, 1861 (Hymenoptera: Formicidae: Ponerinae) in Thailand, with descriptions of three new species, Zootaxa 4526 (2), pp. 151-174 : 159-162

Myopias mandibularis (Crawley, 1924)

( Figs. 22–27 )

Trapeziopelta mandibularis Crawley, 1924: 386 , fig. 3. Holotype worker, INDONESIA, Sumatra, Gunung Dempu , VIII.1916, E. Jacobson leg. (OXUM, syntype image examined). Myopias mandibularis : Bolton, 1995: 269.

Non-type material examined. THAILAND: three workers, Nakhon Si Thammarat Prov., Tha Sala Dist., Mt. San Yen , 19.IV.2007, W. Jaitrong leg., Colony no. WJT1904007-1 (THNHM) ; 4 workers and 1 ergatoid queen, same locality, 22.IV.2007, W. Jaitrong leg., Colony no. WJT07-TH-766 ( THNHM) ; 3 workers, same locality, 16.IV.2007, W. Jaitrong leg., Colony no. WJT07-TH-633 ( THNHM) ; 2 workers and 1 ergatoid queen, same locality, 18.IV.2007, W. Jaitrong leg., WJT07-TH-683 ( THNHM) ; 44 workers and 5 ergatoid queens, Surat Thani Prov., Wipawadee Dist. , 29.XI.2001, W. Jaitrong leg., WJT01-TH-015 ( AMK, BGC, THNHM) ; 1 worker, same locality, 29.XII.2001, W. Jaitrong leg. ( THNHM) ; 1 worker, Ranong Prov., Khlong Naka , 1.I.2000, S. Hasin leg. ( AMK) ; 1 worker, same locality and collector, 30.XII.2000 ( AMK) ; 1 worker, same locality and collector, 31.XII.2000 ( THNHM) .

Measurements. Non-type workers (n = 15): TL 6.24–6.30, HL 1.19–1.25, HW 1.09–1.16, SL 0.79–0.86, ED 0.26–0.30, ML 0.79–0.83, PW 0.83–0.86, MSL 1.72–1.78, PL 0.63–0.66, PH 0.73–0.79, DPW 0.66–0.69, CI 92– 94, SI 71–74, OI 24–26, MI 63–68, LPI 110–121, DPI 100–105.

Diagnosis of worker (figs. 22–24): Body 6.24–6.30 mm in total length (medium size); mandibles broad, narrow at base; masticatory margin of mandibles with five teeth, including large basal tooth, followed by mediumsized prebasal tooth, two minute teeth (denticles), and medium-sized apical tooth; basal margin with a ill-defined protuberance (fig. 6); median clypeal lobe distinctly shorter than broad, its anterior margin with ill-defined tridentate (not clear in some specimens); eyes relatively large; antennal scape not reaching posterior margin of head; in profile, anteroventral corner of head without bluntly angled process; petiole in profile, subrectangular, shorter than high; subpetiolar process well developed, subrectangular, with clearly concave ventral outline, with a downward pointed triangular denticle at anteroventral corner, and with a pair of small posteriorly pointed denticles at posteroventral corners. Dorsum of head with scattered foveae, larger and more elongate along posterior margin of head; ventral surface of head with sparse punctures; scape and mandible smooth and shiny with a few punctures; dorsa of mesosoma, petiole and metasoma segment III with scattered foveae but larger foveae than on head, some elongate; metasoma segment IV largely smooth and shiny with a few punctures; legs smooth and shiny. Body dark to reddish brown; funiculus, mandible, legs and tip of metasoma paler.

Ergatoid queen description (wingless queen, figs. 25–27)

Measurements. Non-type ergatoid queen (n = 7): TL 7.23–7.52, HL 1.22–1.32, HW 1.12–1.22, ED 0.30– 0.33, SL 0.83–0.92, ML 0.73–0.83, PW 0.99–1.06, MSL 1.95–2.15, PL 0.66–0.69, PH 0.79–0.86, DPW 0.76–0.83, CI 92–93, SI 74–76, OI 26–27, MI 59–63, LPI 120–124, DPI 115–119.

Similar to the worker in structure, sculpture, coloration and pilosity, with the following conditions that should be noted: body slightly larger (TL 7.23–7.52 mm in ergatoid queen; 6.24–6.30 mm in worker); head in full-face view clearly longer than broad, rectangular, with weakly convex sides and concave posterior margin; eyes slightly larger than in worker, about twice as long as distance between anterior margin of eyes and mandibular bases; configuration of mandibular dentition and shape of antennal scape similar as in worker; median clypeal lobe distinctly shorter than broad, its anterior margin almost straight or weakly convex; median ocellus larger than lateral ocelli; mesosoma s tout, in profile view pronotum weakly convex dorsal outline; promesonotal suture and metanotal groove distinct and deep; metapleura clearly demarcated from mesonotum by short and shallow furrows and demarcated from metapleura by deep grooves; in dorsal view pronotum about two times as long as mesonotum; mesonotum almost as long as broad, trapezoidal, about 2/3 length of propodeum in dorsal view; dorsum of propodeum weakly convex, rounded into declivity of propodeum; the latter almost flat; petiole in profile subrectangular, slightly shorter than high, its anterior face flat vertical, dorsal outline convex, posterior face flat vertical; in dorsal view, petiolar node trapezoidal and clearly shorter than broad (DPI 115–119); metasoma (segments III to IX) relatively larger than in the worker.

Habitat. This species was found from lowland to highland (500–800 m alt.) in evergreen forest in southern Thailand. All specimens were collected from rotten wood.

Distribution. Thailand (Ranong, Surat Thani, Nakhon Si Thammarat provinces, (new record, fig. 52), Indonesia (Sumatra, Crawley 1924)

Remarks. Myopias mandibularis is most similar to M. modiglianii ( Emery, 1900) in general appearance and having median clypeal lobe tridentate. Myopias mandibularis is distinguished from M. modiglianii as follows: apicomedial process of median clypeal lobe not clearly produced anteriorly (clearly produced anteriorly in M. modiglianii ); basal blade of mandibular masticatory margin of mandibles conspicuously produced medially (weakly produced medially in M. modiglianii ).

Figures

FIGURES 22–24. Myopias mandibularis (non-type worker, WJT07-TH-766). 22, Body in profile view; 23, body in dorsal view; 24, head in full-face view.

FIGURES 25–27. Myopias mandibularis (non-type ergatoid queen, WJT07-TH-766). 22, Body in profile view; 23, body in dorsal view; 24, head in full-face view.