Pristomyrmex rigidus

This species occurs in rainforest and has been taken in litter berlesates and pitfall traps. Wang (2003), in revising the genus, found specimens of this species are two closely related species. With the meager number of specimens available, he felt it was advisable to describe a single species until more material was available to clarify how these two forms differ.

Identification
Wang (2003) - Worker. Antennal fossae reaching the anterior clypeal margin; eyes with six to eight ommatidia in the longest row; pronotum unarmed; dorsal surfaces of head and alitrunk covered fully with well-developed coarse rugoreticulum; dorsum of petiole node with a pair of hairs.

Pristomyrmex rigidus occurs in the Oriental region. It is closely related to Pristomyrmex punctatus. These two species constitute a clade. The separation of the two species is summarized under P. punctatus. Characters separating P. rigidus from the P. divisus-P. pulcher clade are given under Pristomyrmex divisus.

Distribution based on Regional Taxon Lists
Indo-Australian Region: Borneo, Brunei Darussalam, Indonesia, Malaysia. Oriental Region: Thailand, Vietnam.

Castes
Males have yet to be collected.

Nomenclature

 *  rigidus. Pristomyrmex rigidus Wang, M. 2003: 415, figs. 94-97 (w.q.) THAILAND.

Wang (2003) - The material that I have examined may contain two species. Specimens from Thailand possess an anterodorsally angulate postpetiole in profile, a strongly prominent tooth on the basal margin of the mandible, and a truncated basal tooth on the masticatory margin of the mandible. Specimens from Indonesia, Malaysia, and Brunei have a rounded dorsal surface of the postpetiole, a weak tooth on the basal margin of the mandible, and two small basal denticles on the masticatory margin. But a single, variable species is maintained for the present because available material is still limited. Further collecting and studying are needed.

Worker
Holotype TL 3.40, HL 0.98, HW 0.94, CI 96, SL 0.91, SI 97, EL 0.17, PW 0.64, AL 0.86.

TL 2.73-3.44, HL 0.75-0.98, HW 0.74-0.94, CI 93-102, SL 0.70-0.94, SI 91-103, EL 0.14-0.17, PW 0.50-0.64, AL 0.70-0.86, PPW 0.24-0.30, PPL 0.16-0.20, PPI 144-167 (11 = 32).

Mandibles with a few coarse longitudinal rugae that usually do not reach to the vicinity of the masticatory margin. Dentition of the masticatory margin of mandible: the strongest apical tooth + the second strongest preapical + a long diastema + a truncated basal tooth (or two small denticles). A strongly developed tooth or a broad, subtriangular short prominence present about midway on the basal margin of mandible. Clypeus shield shaped, more or less depressed, with a median longitudinal carina that usually does not reach to the anterior clypeal margin; sometimes a few additional weak rugae are present on the clypeus. Anterior clypeal margin usually with a median denticle and three others on each side, but sometimes with a lateral denticle indistinct or two lateral small denticles fused into a larger one. Lateral portions of clypeus reduced to margins, and antennal fossae reaching the anterior clypeal margin. Ventral surface of clypeus usually with two minute toothlike prominences, but sometimes the prominences are very weak. Palp formula .5,3. Frontal carinae extending to the level of the posterior margins of eyes. Antennal scrobes indistinct. Frontal lobes absent, so that the antennal articulations are entirely exposed. Antennal scapes, when lying on the dorsal head, surpassing the occipital margin of head by one-sixth to one-fifth of their length. Eyes containing six to eight ommatidia in the longest row. Occipital margin rather straight or slightly concave. Dorsal surface of alitrunk somewhat convex. Pronotum unarmed. Propodeal spines robust, acute, and long, much longer than the distance between their bases. Metapleural lobes triangular and acute. Pedicel segments in profile. In profile, anterior face of the petiole node, together with the dorsal surface of petiole peduncle, forming a long declivity that reaches the top of the node. Petiole node in profile with an approximately right-angled apex. Dorsum of postpetiole in profile sometimes angulate but sometimes rounded. In dorsal view, postpetiole transverse-rectangular, much broader than long and also broader than the petiole node. Dorsal surfaces of head and alitrunk as well as the sides of pronotum fully covered with coarse rugoreticulum. Sides of the rest of alitrunk with numerous irregular coarse rugae. Sides of petiole node and postpetiole usually with a few rims, but sometimes some of the rims rather weak. Petiole and postpetiole in dorsal view, except for rims, very smooth and polished. Gaster unsculptured. Dorsal surfaces of head and alitrunk with numerous erect or suberect long hairs. A pair of similar hairs present on the dorsal petiole, and usually two pairs on the postpetiole. Two or three pairs of long, forward-projecting hairs present near the anterior clypeal margin. Scapes and tibiae with numerous erect or suberect hairs. First gastral tergite lacking erect or suberect hairs. Color uniformly reddish-brown.

Queen
TL 3.30-4.02, HL 0.85-1.10, HW 0.86-1.10, CI 100-102, SL 0.76-0.88, SI 80-91, EL 0.18-0.24, PW 0.66-0.86, AL 0.84-1.08, PPW 0.28-0.36, PPL 0.20-0.22, PPI 140-164 (n = 6).

Generally similar to worker, except for caste differences; in addition, the sculpture of mesoscutum is weaker and sparse.

Type Material
Holotype Worker:. Thailand: 26. Kaeng Krachan NP., 19.xi.1985 (LobI and Burckhardt). Paratypes: 11 workers (, BMNH, ) same data as holotype.