Solenopsis tetracantha

Solenopsis tetracantha has been collected in a nest of Acromyrmex lundii in La Plata, Argentina (Forel 1912).

Identification
A New World thief ant. It's morphology shows affinities with the molesta and fugax complexes. (Key to New World Solenopsis Species Complexes)

Pacheco and Mackay (2013) - Minor worker - This is a small shiny, yellow species. The head is noticeably elongate and resembles species of the pygmaea complex, but can be distinguished by the fine head punctures instead of coarse punctures present in the pygmaea group. The anterior clypeal margin is also elongate and the clypeal carinae are well defined with the lateral clypeal teeth present and well developed, but the extralateral clypeal teeth are only angulate. The eye is small with only one or two ommatidia. The posterior margin of the propodeum is rounded. The petiole is barely wider than the postpetiole in profile and has a tooth ventrally. Major worker - This is one of the very few species that is dimorphic. The major is concolorous golden yellow and slightly darker than the minor worker. The head is noticeably elongate and coarsely punctate. Both the lateral and extralateral teeth are well developed. The eye is small with one ommatidium. The scapes are short and barely extend past the middle of the head. The pronotum has a flat dorsal slope. The petiole is thick, robust and the node extends laterally, with a subpeduncular tooth. Queen - The queen is medium brown in color. All four clypeal teeth are present and well developed. The clypeal carinae are weakly defined. The propodeum is horizontally striated. The petiolar peduncle has a well-developed tooth ventrally.

Distribution based on Regional Taxon Lists
Neotropical Region: Argentina, Paraguay.

Castes
Dimorphic workers.

Nomenclature

 *  tetracantha. Solenopsis tetracantha Emery, 1906c: 131, fig. 13 (w.q.) ARGENTINA. Santschi, 1917f: 281 (m.). Current subspecies: nominal plus videns.
 * videns. Solenopsis tetracantha var. videns Forel, 1912g: 4 (w.) ARGENTINA. Junior synonym of tetracantha: Pacheco & Mackay, 2013: 329.

Worker
Pacheco and Mackay (2013) - Major. Measurements (n=1). TL 1.92; HL 0.570; HW 0.450; EL 0.036; ED 0.030; SL 0.312; FSL 0.138; CI 78.9; SI 54.7; PL 0.108; PW 0.162; PI 66.7; PPL 0.120; PPW 0.168; PPI 71.4; WL 0.444; PSL 0.030; PSW 0.030.

Moderately large, concolorous golden brown; head noticeably elongate; lateral clypeal teeth well developed, elongate, extending 0.030 mm past anterior margin, extralateral teeth reduced, smaller than lateral teeth; clypeal carinae well defined; eye small, one ommatidium; scape barely exceeds past middle of head; pronotum flat dorsally; posterior propodeal margin angulate; metapleuron horizontally striated; petiole robust, thickened laterally, peduncle with sharp tooth ventrally; postpetiole oval viewed dorsally.

Hairy, pilosity yellow; most hairs erect and suberect (0.060 mm) covering all body surfaces; hairs on petiole and postpetiole curve posteriorly.

Minor. Measurements (n=4). TL 1.32-1.44 (l.40); HL 0.390-0.462 (0.424); HW 0.300-0.330 (0.318); EL 0.018-0.030 (0.024); ED 0.018-0.024 (0.022); SL 0.228-0.312 (0.266); FSL 0.090-0.132 (0.104); CI 70.1-78.6 (75.2); SI 58.5-67.5 (62.5); PL 0.066-0.078 (0.072); PW 0.090-0.120 (0.107); PI 60.0-80.0 (68.4); PPL 0.078; PPW 0.114-0.132 (0.123); PPI 59.1-68.4 (63.6); WL 0.276-0.300 (0.289); PSL 0.024-0.030 (0.027); PSW 0.024.

Small, concolorous golden yellow; head elongate, much longer than wide; coarsely punctate; anterior clypeal margin elongate, extends anteriorly; clypeal carinae well defined; lateral clypeal teeth well developed, extralateral teeth angulate; scape barely exceeding head medially; eye small with one ommatidium; pronotum flat dorsally; notopropodeal suture well depressed, groove breaks sculpture of mesosoma; posterior margin of propodeum rounded; petiole barely wider than postpetiole in profile, with sharp peduncular tooth ventrally.

Moderately hairy with some hair present on all body surfaces; pilosity yellow, mainly suberect hairs of different lengths; head more heavily pilose than rest of body; hairs on petiole and postpetiole curve posteriorly.

Queen
Pacheco and Mackay (2013) - Measurements (n=2). TL 5.40; HL 0.810-0.822 (0.816); HW 0.660-0.720 (0.690); EL 0.240-0.258 (0.249); ED 0.222-0.228 (0.225); MOL 0.072; MOD 0.072-0.078 (0.075); SL 0.540; FSL 0.300-0.312 (0.306); CI 80.3-88.9 (84.6); SI 65.7-66.7 (66.2); PSL 0.066-0.072 (0.069); PSW 0.060-0.078 (0.069); PL 0.228-0.240 (0.234); PW 0.330; PI 69.1; PPL 0.360; PPW 0.402; PPI 89.6; WL 1.08-1.20 (1.14).

Moderately large; concolorous medium brown; head longer than wide, coarsely punctate; lateral clypeal teeth and extralateral teeth well developed; clypeal carinae weakly defined; scape long, nearly reaching posterior border of head; eyes large; medial ocellus small; pronotum coarsely punctate, smooth and shiny between punctures; propodeum horizontally striated below spiracle; petiole and postpetiole horizontally striated; petiolar peduncle with well-developed tooth ventrally. Moderately hairy, pilosity yellow; erect and suberect covering all body surfaces, hairs on pronotum 0.012 mm in length.

Type Material
Emery 1906, Museo Civico coll. C. Emery (dono 1925), Argentina, La Plata (Bruch leg), Nunez, 21.vi.99 (lectotype worker, 2 paralectotype workers and 2 paralectotype queens [here designated] ). Solenopsis tetracantha videns, Forel Coll., Argentina, La Plata (D'Bruch) (lectotype worker [here designated] ).