Solenopsis subtilis

Solenopsis subtilis has been collected in leaf litter extractions from lowland forest, cloud forest, transition montane/cloud forest, and montane evergreen forest between 1000- 1800 m.

Identification
A New World thief ant that is a member of the molesta species complex. (Key to New World Solenopsis Species Complexes)

Pacheco and Mackay (2013) – Worker - The worker is small and light brown in color with yellowish appendages. The clypeal carinae are slanted medially, anteriorly to posteriorly between the frontal carinae. The eye is small with 3-5 ommatidia. The notopropodeal suture is notch-shaped and the groove breaks the sculpture of the mesosoma. The propodeal spiracle is small at 0.024 mm in diameter. Queen - (undescribed). The queen is small (TL 2.7 mm), abundantly pilose and medium brown with golden brown appendages. The lateral clypeal teeth are angulate with bumps present in the extralateral position. The head and pronotum are semi-coarsely punctated. The metapleuron, petiole and postpetiole are horizontally striated. Both the petiolar peduncle and postpetiole lack a tooth or flange ventrally.

Solenopsis subtilis may be confused with Solenopsis sulfurea, another member of the South American tenuis subgroup. The workers of S. sulfurea have an elongated clypeus, weakly defined clypeal carinae and an eye with a maximum of three ommatidia, while S. subtilis workers have a compact clypeus, well defined clypeal carinae and a slightly larger eye with a maximum of five ommatidia. Additionally, the queen of S. sulfurea is golden brown, slender bodied; with 4 teeth present on the clypeus and the petiole and postpetiole have punctate/roughened sculpturing when viewed laterally. The queen of S. subtilis is medium brown with golden brown appendages, has a clypeus with two teeth present and the petiole and postpetiole are horizontally striated.

The workers of Solenopsis subtilis are nearly identical to those of Solenopsis picta, a species found in North America, in the southern Gulf Region, but are much lighter in color. The queens of the two species are different as the queen of S. picta lacks striae on the petiole and postpetiole.

Solenopsis subtilis is similar to the Galapagos species, Solenopsis gnoma, as well, but can be distinguished as S. gnoma has an elongated clypeus. Additionally, if a queen is collected, the petiole and postpetiole of S. gnoma has roughened sculpturing.

The workers from Bolivia are here considered S. subtilis however vary from the type in being lighter in coloration (yellow to golden yellow vs. light brown), having more developed lateral clypeal teeth and a less thickened petiole when viewed laterally. Color is a variable character within the thief ants as well as clypeal teeth development as seen with Solenopsis clytemnestra for example.

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

Castes
Males have yet to be collected.

Nomenclature

 * . Solenopsis subtilis Emery, 1896g: 90, pl. 1, fig. 16 (w.) PARAGUAY, VENEZUELA.
 * Type-material: 3 syntype workers.
 * Type-locality: Paraguay: (no further data) (Balzan) (by restriction of Pacheco & Mackay, 2013: 311).
 * [Note: other original syntype locality: Venezuela: Caracas (Thieme).]
 * Type-depository: MSNG.
 * Pacheco & Mackay, 2013: 310 (q.).
 * Status as species: Mann, 1916: 447; Emery, 1922e: 201; Santschi, 1923c: 259; Ettershank, 1966: 143; Kempf, 1972a: 240; Bolton, 1995b: 391; Wild, 2007b: 37; Pacheco & Mackay, 2013: 309 (redescription).
 * Distribution: Bolivia, Brazil, Paraguay, Venezuela.

Worker
Pacheco and Mackay (2013) - Measurements (n=2). TL 1.44-1.56 (1.50); HL 0.420-0.432 (0.426); HW 0.360; EL 0.042; ED 0.030; SL 0.300; FSL 0.126; CI 83.3-85.7 (84.5); SI69.4-71.4 (70.4); PL 0.072-0.078 (0.0750); PW 0.102; PI 70.6-76.5 (73.5); PPL 0.078-0.084 (0.081); PPW 0.120-0.126 (0.123); PPI 61.9-70.0 (65.9); WL 0.282-0.300 (0.291); PSL 0.024; PSW 0.024.

Small; concolorous light brown, yellowish appendages; head quadrate, longer than wide, finely punctate; lateral clypeal teeth developed, but short, extralateral teeth reduced to bumps; clypeal carinae well defined; scapes long, thin (0.036 mm at widest diameter), nearly reaching posterior border of head; minor funicular segments 3-8 long; eyes black, small, 3-5 ommatidia; pronotum smooth and shiny; notopropodeal suture well depressed, notch-like, groove breaks sculpture of mesosoma; mesopleuron smooth and shiny; posterior propodeal margin rounded; propodeal spiracle round, small; metapleuron horizontally striated; petiole wider than postpetiole viewed laterally; petiolar node triangular, peduncle lacking tooth but with thin flange ventrally; postpetiolar node semicircular, lacking tooth or flange ventrally.

Moderately hairy, pilosity yellow; long (0.090-0.120 mm), erect and suberect hairs scattered on body surfaces; hairs on petiole, postpetiole, gaster curve posteriorly.

Queen
Pacheco and Mackay (2013) - Measurements (n=3). TL 2.64-2.76 (2.70); HL 0.516-0.540 (0.526); HW 0.432-0.462 (0.442); EL 0.162-0.168 (0.164); ED 0.144-0.150 (0.146); MOL 0.048-0.054 (0.050); MOD 0.048-0.060 (0.054); SL 0.360-0.372 (0.364); FSL 0.168-0.180 (0.174); CI 82.8-85.6 (84.0); SI 68.9-69.8 (69.2); PSL 0.054; PSW 0.048; PL 0.102-0.114 (0.108); PW 0.192-0.210 (0.198); PI 53.1-56.3 (54.6); PPL 0.150; PPW 0.222-0.228 (0.226); PPI 65.8-67.6 (66.4); WL 0.648-0.720 (0.680).

Small; medium brown with golden brown appendages; head quadrate, semi-coarsely punctated, straight posterior border; lateral clypeal teeth angulate; bumps at extralateral position; clypeal carinae well defined; frontal lobes lack horizontal striae; scapes do not reach posterior lateral corner of head; eye moderately large, medial ocellus small; pronotum semi-coarsely punctated, smooth and shiny between punctures, mesopleuron lacking sculpturing; metapleuron horizontally striated; propodeal spiracle small; posterior propodeal margin weakly angulate; both petiole and postpetiole horizontally striated, peduncle lacking tooth or flange ventrally.

Abundantly hairy; pilosity yellow; erect and sub erect hairs of various lengths (0.030-0.120 mm) cover all body surfaces.

Type Material
Syntypus, 1896, Museo Genova, Coll. C. Emery [dono 1925], Paraguay (Balzan) (3 syntypes workers seen ).

References based on Global Ant Biodiversity Informatics

 * Emery C. 1896. Studi sulle formiche della fauna neotropica. XVII-XXV. Bullettino della Società Entomologica Italiana 28: 33-107.
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Pacheco J. A., and W. P. Mackay. 2013. The systematics and biology of the New World thief ants of the genus Solenopsis (Hymenoptera: Formicidae). Lewiston, New York: Edwin Mellen Press, 501 pp.
 * Santschi F. 1923. Solenopsis et autres fourmis néotropicales. Revue Suisse de Zoologie 30: 245-273.
 * Wild, A. L. "A catalogue of the ants of Paraguay (Hymenoptera: Formicidae)." Zootaxa 1622 (2007): 1-55.