Tetramorium saudicum

Tetramorium saudicum was observed nesting directly in the ground and many workers were observed carrying dry plant seeds.

Identification
Sharaf 2013 - Tetramorium saudicum is a member of the caespitum-group. It can be readily separated from its closest congener, the Palaearctic Tetramorium striativentre from Kazakhstan by the bicoloured body, head, mesosoma, waist and appendages reddish brown, gaster brownish or blackish brown; whereas T. striativentre is unicolorous brownish and the appendages are pale brown. Both species are similar in body size, mesosomal and gastral sculpture, and the frontal carina that extend back to the posterior margins of eyes. Tetramorium saudicum also differs from T. striativentre by the following: the head dorsum is polished with few (nearly 10) fine longitudinal rugulae superimposed upon irregularly punctulate ground-sculpture while in T. striativentre, the head dorsum is dull with numerous (nearly 20) very fine longitudinal rugulae superimposed upon a finely and densely punctulate or granular ground-sculpture. In addition, the petiolar node of T. saudicum in dorsal view is clearly irregularly rugulose, whereas in T. striativentre the petiolar node in dorsal view is clearly regularly longitudinally rugulose. Tetramorium saudicum can be distinguished from the remaining Arabian species of the genus (except T. sericeiventre and T. khyarum) by the sculptured first gastral tergite. It can be separated from Tetramorium sericeiventre and Tetramorium khyarum by the following characters: the scape index is much smaller, SI 63–71 (versus SI 113–118 for khyarum and SI 101–118 for sericeiventre); the head length is smaller, HL 0.75–0.85 (Versus HL 0.96–1.00 for khyarum and HL 0.80–1.00 for sericeiventre) and eyes relatively larger, EL 0.20–0.25 (versus EL 0.20 for khyarum and EL 0.16–0.22 for sericeiventre).

Distribution based on Regional Taxon Lists
Afrotropical Region: Saudi Arabia.

Nomenclature

 *  saudicum. Tetramorium saudicum Sharaf, 2013: 574, figs. 6e, f, g (w.) SAUDI ARABIA.

Worker
Holotype worker: TL 3.12; HL 0.80; HW 0.80; SL 0.55; EL 0.22; PRW 0.52; ML 0.87; PL 0.22; PW 0.25; PPL 0.22; PPW 0.30; Indices: SI 69; CI 100. Paratype workers: TL 3.12–3.25; HL 0.75–0.85; HW 0.75–0.80; SL 0.50–0.55; EL 0.20–0.25; PRW 0.50– 0.55; ML 0.85–0.92; PL 0.17–0.22; PW 0.25–0.27; PPL 0.17–0.22; PPW 0.25–0.30; Indices: SI 63–71; CI 91–100 (11 measured).

Head: Head as long as wide or subequal, with convex sides and nearly straight posterior margin; anterior clypeal margin entire; ventral surface of head with few ammochaete setae; frontal carinae present, running back beyond level of posterior margin of eyes but feebly developed throughout their length and weaker behind eyes than in front; eyes large (EL about 0.29 x HW) with about 15 ommatidia in longest row; ventral margin of eyes more or less flat, anterior, dorsal and posterior margins curved so that eyes in profile resembling reclinate letter D; mandibles longitudinally rugose; antennae 12-segmented; antennal scrobes absent; entire dorsum and profile of head very finely and very densely longitudinally costulate, spaces between costulae finely, irregularly and densely punctulate; dorsum of head with many paired hairs. Mesosoma: Outline of dorsal mesosoma unbroken in profile; pronotal humeri sharply angulate; metanotal groove not impressed; propodeal spines acute and strongly developed; dorsal (outer) surface of hind tibiae with appressed pubescence; propodeal dorsum with a single pair of short hairs; mesosoma strongly longitudinally rugulose, space between regulae smooth and shining. Waist: Petiole cuboid; petiolar and postpetiolar nodes in dorsal view distinctly broader than long; petiole with one pair of hairs, postpetiole with three pairs of hairs; petiolar node in dorsal view clearly irregularly rugulose; postpetiolar node distinctly strongly longitudinally rugulose. Gaster: First gastral tergite longitudinally, very finely and very densely striated, appearing dull; gaster with scarce scattered erect hairs and moderately dense appressed pubescence. Bicoloured species, head, mesosoma, petiole, postpetiole and appendages reddish brown, gaster brownish or blackish brown.

Type Material
Holotype worker. Saudi Arabia, Riyadh, Rawdhat Khorim, 24.III.2012, 25.23°N, 47.17°E, 559 m (M. R. Sharaf); unique specimen identifier CASENT0281582, deposited at KSMA. Paratypes: 21 workers, same data as the holotype; 2 workers, Saudi Arabia, Jazan, Al Zabia 9.IV.2012, 17.06°N, 42.39°E, 43 m (M. R. Sharaf); 2 workers, Shaqiq Shamran, IV.1983 (C. A. Collingwood); 2 workers, Riyadh, III.1989 (soil fauna); 15 workers, Riyadh, Rawdhat Khorim, [multiple dates]; one paratype deposited in each of the following museums: MHNG, NHMB, CASC, MCZC, SEMC, WMLC, BMNH, and the remaining specimens at KSMA.

Etymology
The name of this species, saudicum, refers to the type locality, the Kingdom of Saudi Arabia.

References based on Global Ant Biodiversity Informatics

 * Sharaf M. R., M. S. Abdel-Dayem, H. M. Al Dhafer, and A. S. Aldawood. 2013. The ants (Hymenoptera:formicidae) of Rawdhat Khorim Nature Preserve, Saudi Arabia, with description of a new species of the genus Tetramorium Mayr. Zootaxa 3709(6): 565-580.