Pristomyrmex costatus

Swamp forest, rainforest, nest ex rotten log, lowland rainforest, on rotten log and in leaf litter, primary forest, sifting under bark.

Identification
Wang (2003) - Worker. Ventral surface of clypeus lacking a developed tooth, but usually with a transverse ruga; pronotal spines fairly long, ca. 1.5 to 2 times the length of propodeal armaments, but distinctly shorter than the distance between the bases of two pronotal spines; dorsal surfaces of head and alitrunk sculptured with coarse rugoreticulum; petiole node lacking foveolate punctures; first gastral tergite lacking erect or suberect hairs.

Pristomyrmex costatus is extremely similar in appearance to another Oriental species, Pristomyrmex sulcatus. The workers and queens of the two species can be separated as follows: In P. costatus, the ventral surface of the clypeus lacks a toothlike prominence, usually with a transverse ruga; in P. sulcatus, the ventral center of the clypeus has an acutely prominent tooth and no transverse ruga. The separation of P. costatus from Pristomyrmex modestus and from Pristomyrmex bicolor is summarized under the latter names.

A member of the Quadridens species group / Key to Pristomyrmex workers

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Malaysia, Philippines, Singapore.

Nomenclature

 *  costatus. Pristomyrmex costatus Wang, M. 2003: 434, figs. 123-126 (w.q.) WEST MALAYSIA.

Worker
Holotype. TL 4.14, HL 0.99, HW 0.96, CI 97, SL 0.96, SI 100, EL 0.21, PW 0.68, AL 1.12, PPW 0.30, PPL 0.30, PPI 100. Paratypes, 3 workers: TL 4.48-4.54, HL l.04-1.08, HW 0.98-1.02, C1 94-94, SL 1.07-l.12, SI 108-110, EL 0.20-0.20, PW 0.68-0.72, AL l.18-l.24, PPW 0.30- 0.31, PPL 0.33-0.34, PP1 91-94.

Mandibles usually with several longitudinal rugae. Masticatory margin of mandible with four teeth arranged as two adjacent strong apical teeth + a long diastema + two small basal teeth of similar size. Basal margin of mandible lacking a distinctly curved lobe or tooth. Clypeus with a strong median longitudinal carina. Anterior clypeal margin with a median denticle and two to three others on each side. Ventral surface of clypeus possessing or lacking a transverse ruga, never armed with a developed, acute tooth. Palp formula 1,3. Frontal carinae strong, extending to the level of the posterior margins of eyes. Slightly concave scrobal areas present lateral to the frontal carinae. Frontal lobes weak so that the antennal articulations are almost entirely exposed. Antennal scapes, when lying on the dorsal head, slightly surpassing the occipital margin of head. Eyes containing 9 to 10 ommatidia in the longest row. Pronotum armed with a pair of strong and fairly long spines that are ca. 0.19 to 0.27, 1.5 to 2 times the length of propodeal armaments, but distinctly shorter than the distance between the bases of two pronotal spines. Propodeum with a pair of acute short spines that are ca. 0.10 to 0.16 and more slender than the pronotal ones. Metapleural lobes subtriangular. Petiole node in profile, slightly higher than long, with a fairly long anterior peduncle; its anterodorsal angle is on a higher level than the posterodorsal. Postpetiole in profile rounded dorsally, in dorsal view broadening from front to back. Dorsum of head, except for the scrobal areas where there are only some transverse rugae, with well-developed coarse rugoreticulum. Similar sculpture present on the sides of pronotum and the dorsum of alitrunk. Petiole with a coarse longitudinal ruga on each side, but dorsum of petiole node unsculptured and smooth. Dorsum of postpetiole unsculptured and smooth. Gaster smooth and shining. Dorsal surfaces of head and alitrunk with numerous erect or suberect long hairs. Sides and dorsum of petiole node and postpetiole with five or more pairs of hairs in the type specimens. First gastral tergite lacking erect or suberect hairs. Several pairs of forward-projecting hairs present near the anterior clypeal margin. Scapes and tibiae with some erect to suberect hairs. Color reddish-brown.

Queen
Two queens, respectively, from N. Borneo and Sarawak, with the following measurements: TL 5.24, .5.26; HL 1.12, 1.20; HW l.16, l.22; CI 102, 104; SL 1.18, l.20; SI 98, 102; EL 0.28, 0.31; PW 1.00, 1.10; AL 1.44, 1.62; PP\V 0.38, 0.44, PPL 0.40, 0.44, PPI 95, 100.

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

Type Material
Holotype Worker. . Malaysia: Neg. Sembilan, Pasoh For. Res., xi. 1994, (M. Brendell, K. Jackson, and S. Lewis). Paratypes. . Three workers, N. Borneo (E. Mjoberg).