Tetramorium triangulatum

This species is uncommon in the Shivalik range of the north-western Himalaya and was collected from soil.

Identification
Bharti and Kumar (2012) - Tetramorium triangulatum belongs to the inglebyi-species group (Bolton 1977) which is apparently restricted to India and is easily characterized by antennae 12-segmented, appendage of sting triangular or dentiform, frontal carinae absent or very short, not reaching the level of the anterior margin of the eyes, eyes small, reduced to a single ommatidium in Tetramorium myops, antennal scrobes absent, base of first gastral tergite strongly concave in dorsal view, the anterolateral angles of the sclerite angular, produced as a short tubercles or tooth on each side of the posterolateral corners of the postpetiole.

This new species is close to Tetramorium myops as both species possess short frontal carinae, minute eyes, peduncle with ventral lamella and an medially impressed anterior clypeal margin. However, this new species can be easily distinguished from T. myops by the following combination of characters: T. triangulatum sp. n. has short propodeal spines (PSL 0.07mm), triangular and divergent, peduncle with a large and straight lamella ventrally, dorsum of mesosoma longitudinally rugulose, base of first gastral tergite longitudinally rugulose, while in case of T. myops the propodeal spines are long and upcurved along their length, the peduncle with a large rounded and convex lamella ventrally, dorsum of mesosoma with longitudinal rugulae and reticulation, base of first gastral tergite with vestiges of superficial sculpture. Some of the other significant characters of T. triangulatum sp. n. which differentiate it from T. myops are: head broader posteriorly with straight sides and SI 71.11-75.00 versus head with convex sides and SI 77.00-83.00 in T. myops.

Distribution based on Regional Taxon Lists
Oriental Region: India.

Nomenclature

 *  triangulatum. Tetramorium triangulatum Bharti & Kumar, 2012: 16, figs. 4-12 (w.q.m.) INDIA.

Worker
Holotype. HL 0.60, HW 0.52, SL 0.38, EL 0.03, WL 0.63, PW 0.37, PSL 0.07, PTL 0.14, PPL 0.20, PTW 0.19, PPW 0.21, PTH 0.21, PPH 0.19, CI 86.67, OI 5.77, SI 73.08, PSLI 11.67, PeNI 51.35, LPeI 66.67, DPeI 135.71, PpNI 56.76, LPpI 105.26, DPpI 105.00, PPI 110.53.

Paratype workers. HL 0.53-0.60, HW 0.45-0.52, SL 0.32-0.38, EL 0.03, WL 0.57-0.63, PW 0.31-0.37, PSL 0.07, PTL 0.12-0.14, PPL 0.17-0.20, PTW 0.16-0.19, PPW 0.19-0.21, PTH 0.19-0.21, PPH 0.16-0.19, CI 84.91-86.67, OI 5.77-6.67, SI 71.11-75.00, PSLI 11.67-13.21, PeNI 50.00-51.61, LPeI 63.16-70.00, DPeI 121.43-135.71, PpNI 56.76-61.76, LPpI 89.47-106.25, DPpI 105.00-123.53, PPI 110.53-123.53 (8 measured).

Head longer than broad, sides weakly convex or almost straight with rounded posterolateral corners, broader posteriorly than anteriorly; posterior head margin straight; clypeus convex with steep apical half; anterior margin of clypeus with a narrow transverse plate like fringe and somewhat impressed medially; mandibles triangular with 7 teeth, masticatory margin of mandibles with large apical and preapical tooth; third tooth slightly smaller than the preapical tooth followed by 4 denticles; frontal lobes weakly developed, frontal area indistinct; antennal scrobes absent; eye small in size, located laterally and below mid-length of head, composed of single ommatidium; antennae slender, 12-segmented; scape not reach to posterior head margin and 0.63× head length; mesosoma slightly longer than head, broader anteriorly than posteriorly, dorsum flat, tapering backwards; promesonotal suture and metanotal groove indistinct; propodeal spine short (PSL 0.07 mm), triangular, acute, divergent and slightly longer than propodeal lobes; propodeal lobes triangular and acute; posterior declivity of propodeum short, concave; petiolar node as broad as long in dorsal view; weakly convex dorsum in lateral view; peduncle short, with a large, straight lamella ventrally; postpetiole broader than long, base of first gastral tergite concave behind the postpetiole, anterolateral corners prominent and projecting forward as a pair of blunt teeth or horns which go round the sides of the posterior portion of the postpetiole, gaster oval.

Head longitudinally rugulose, interrugal space somewhat granular, punctured and shiny; frontal carinae very short, ending in front of the level of the eyes; mandibles longitudinally rugulose and finely punctured; clypeus longitudinally carinate and these carinae continued to head sculpture; dorsum of mesosoma longitudinally rugulose and interrugal space somewhat granular, punctured; sides of mesosoma finely rugoreticulate; petiole and postpetiole mostly smooth with traces of rugosity; propodeal declivity with traces of fine transverse rugosity, base of first gastral tergite longitudinally rugulose; legs smooth except coxae faintly punctured.

Body yellowish brown; whole body covered with long and short, erect and suberect pilosity; antennal scapes and hind tibiae with short suberect hairs.

Queen
HL 0.67-0.71, HW 0.62-0.63, SL 0.42-0.44, EL 0.17-0.19, WL 0.94-0.98, PW 0.57-0.59, PSL 0.13-0.14, PTL 0.14-0.19, PPL 0.24-0.25, PTW 0.23-0.27, PPW 0.30-0.32, PTH 0.28-0.30, PPH 0.27-0.30, CI 88.73-92.54, OI 26.98-30.16, SI 67.74-69.84, PSLI 18.31-19.72, PeNI 38.98-45.76, LPeI 50.00-63.33, DPeI 135.29-171.43, PpNI 50.85-54.24, LPpI 83.33-88.89, DPpI 125.00-128.00, PPI 118.52-130.43 (3 measured).

Similar to the worker in structure, sculpture and pilosity except the following characters (besides characters related to wings): eyes large in size, head with three ocelli.

Male
HL 0.50-0.52, HW 0.46-0.48, SL 0.23-0.24, EL 0.23, WL 1.02-1.05, PW 0.66-0.69, PTL 0.14-0.16, PPL 0.21-0.24, PTW 0.21-0.23, PPW 0.27-0.28, PTH 0.23-0.24, PPH 0.23-0.25, CI 92.00-92.31, OI 47.92-50.00, SI 50.00, PeNI 31.82-34.33, LPeI 58.33-69.57, DPeI 131.25-164.29, PpNI 39.13-42.42, LPpI 84.00-104.35, DPpI 112.50-133.33, PPI 117.39-133.33 (3 measured).

Head slightly longer than broad, sides convex, posterior head margin convex, with three ocelli; mandibles with well developed 5 pointed teeth but in few specimens large apical teeth followed by series of denticles; clypeus convex and its anterior margin entire, convex with a narrow transverse plate like fringe and not impressed medially; frontal lobes reduced; antennae 10-segmented; scape short and not reach to posterior head margin and almost 0.46× times head length; apical segment longer and twice of preapical segment, followed by 4 segments as long as broad; then followed by a segment slightly longer than broad; antennal segment attached to pedicel much longer and almost equal to apical segment which then followed by a small segment (smaller than all flagellar segments); antennal scrobes absent; eyes large, convex, situated laterally and more towards lower half of head; pronotum broader than head with rounded anterior lateral angles; mesoscutum and mesoscutellum flat; propodeal dorsal face flat and oblique with vertical declivitous part; propodeal spines absent; propodeal lobes almost rounded; petiole longer, almost 1.4× times its width, with a ventral lamella along its entire length; Postpetiole broader than long; gaster convex, elongate, oval; longer legs.

Head and clypeus longitudinally rugulose and spaces between them punctured; mandibles punctured, frontal carinae continued to the posterior ocelli; dorsum and sides of mesosoma smooth and shiny except propodeum; propodeum finely longitudinally rugulose and punctured; node of petiole, postpetiole, gaster and legs smooth and shiny except few trace of sculpture on sides of node of petiole; wings transparent.

Body yellowish brown with 1st gastral tergite much darker and area of ocelli blackish; body covered with short and long suberect pilosity.

Type Material
Holotype. Worker, India, Himachal Pradesh, Andretta, 32.036638°N, 76.566532°E, 940m alt., soil core, 19 June 2010, coll. R. Kumar,. Paratypes. 15(q), India, Punjab, Patiala, 250m alt., soil core, 13 July 1999, coll. H. Bharti; 25(m), India, Punjab, Patiala, 250m alt., soil core, 13 July 1999, coll. H. Bharti; 1(w), India, Uttarakhand, Assan Barrage, 440m alt., soil core, 10 May 2009, coll. R. Kumar; 46(w), India, Himachal Pradesh, Andretta, 940m alt., soil core, 19 June 2010, coll. R. Kumar; 7(m), India, Himachal Pradesh, Andretta, 940m alt., soil core, 19 June 2010, coll. R. Kumar; 10(q), India, Himachal Pradesh, Andretta, 940m alt., soil core, 19 June 2010; coll. R. Kumar; and two paratype will be deposited in.

Etymology
The specific epithet refers to the triangular propodeal spines.

References based on Global Ant Biodiversity Informatics

 * Bharti H., and R. Kumar. 2012. Taxonomic studies on genus Tetramorium Mayr (Hymenoptera, Formicidae) with report of two new species and three new records including a tramp species from India with a revised key. Zookeys 207: 11-35.