Pristomyrmex trachylissus

This species occurs in rainforest and has been collected on a rotten log.

Identification
Wang (2003) - Worker. Large size (HL > 1.36, HW > 1.45); masticatory margin of mandible with five teeth; pronotum with a pair of exceptionally long spines that are about as long as the distance between their bases.

Pristomyrmex trachylissus must have evolved from the ancestor of Pristomyrmex bicolor: It is extremely similar in appearance of the workers and queens to P. bicolor: The two species may occur sympatrically in Sarawak and in Sabah. Their workers and queens can be separated by the following characters: P. trachylissus - Masticatory margin of mandible with five teeth; diastema indistinct or very short. Basal margin of mandible with a central, broadly curved lobe. Anterior clypeal margin with a median tooth and a broad, short prominence on each side SI < 100 (only in worker). P. bicolor - Masticatory margin of mandible with four teeth; a long diastema present between the preapical and the third tooth. Basal margin of mandible lacking a distinctly curved lobe Antelior clypeal margin usually with seven denticles, but in some specimens, two or three lateral denticles fused into a broadly convex lobe. SI > 105 (only in worker).

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo. Oriental Region: Thailand.

Nomenclature

 *  trachylissus. Myrmica trachylissa Smith, F. 1858b: 126 (q.) BORNEO. Mayr, 1886c: 359 (w.). Combination in Pristomyrmex: Mayr, 1886c: 359. Wang, M. 2003: 474 (w.). See also: Emery, 1887b: 450.

Worker
Wang (2003) - TL 5.58-6.48, HL l.36-l.46, HW 1.45-l.62, C1 107-114, SL l.40-l.50, S1 90-98, EL 0.22-0.24, PW 0.92-l.02, AL l.50-l.64, PPW 0.35-0.39, PPL 0.44-0.48, PP1 76-83 (n = 6).

Mandibles generally smooth and shining, except for a few superficial rugae. Masticatory margin of mandible with five teeth arranged as the strongest apical + the second strongest preapical + a small third tooth + a short diastema (or this diastema indistinct) + two small basal teeth. Basal margin of mandible with a central, broadly curved lobe. Clypeus with a strong median longitudinal carina. Anterior clypeal margin with a median denticle and a broad prominence on each side. Ventral surface of clypeus generally smooth and shining but sometimes with a weak, short, transverse ruga at the center. Frontal carinae strong, extending to the level of the posterior margins of the eyes. Antennal scrobes shallow, present lateral to the frontal carinae. Frontal lobes weak; thus, the antennal articulations are almost entirely exposed. Antennal scapes, laid on the dorsal head, slightly surpassing the occipital margin of head. Eyes with 10 to 11 ommatidia in the longest row. Pronotum armed with a pair of robust, exceptionally long spines, ca. 0.40 to 0.50, about as long as the distance between their bases. Propodeum with a pair of short spines, ca. 0.12 to 0.18, shorter than or at most about as long as the distance between the bases of two propodeal spines. Metapleural lobes each with a somewhat blunt-rounded apex. Petiole node in profile high, with a long anterior peduncle; its anterodorsal angle is on a higher level than the posterodorsal. Postpetiole in profile rounded dorsally, in dorsal view longer than broad and broadening from front to back. Dorsum of head entirely sculptured with well-developed coarse rugoreticulum. Similar sculpture present on the dorsum of alitrunk and on the two sides of pronotum, except for the space between the bases of two pronotal spines, which is rather smooth. Petiole smooth and shining but with a lateral longitudinal carina on each side. Postpetiole and gaster unsculptured, smooth, and shining. Dorsal surfaces of head and alitrunk with numerous erect or suberect hairs. A few pairs of hairs pre sent on the dorsum of petiole node and at least a pair on the postpetiole. First gastral tergite lackng erect or suberect hairs. A few pairs of forward-projecting hairs present near the anterior clypeal margin. Scapes and tibiae with some erect or suberect hairs. Color reddish-brown, but the masticatory margins and the basal margins of mandibles and the funiculi of antennae black-brown.

Queen
Wang (2003) - TL 7.55, HL l.84, HW 2.14, CI 116, SL- (antennal scapes missing), SI-, PW 1.52, AL 2.10 (n = 1).

General shape with normal caste differences from the conspecific worker; pronotum unarmed; other characters similar to worker.

Type Material
Wang (2003) - Holotype queen, Borneo (A. H. Wallace) [examined].