Solenopsis nigella

This species was collected foraging on sand in northern Argentina (Forel 1912).

Identification
A New World thief ant that is a member of the nigella species complex.

Pacheco and Mackay (2013) – Worker - This is a concolorous golden brown ant that is shiny and with little body hair. The head is relatively large. The anterior margin of the head as well as the frontal lobes have vertical striae. The lateral clypeal teeth are present and well defined while the extralateral teeth are absent. The clypeal carinae are well developed. The scape is thin and short, barely exceeding the midpoint of the head. This ant has a large eye with about 30-35 ommatidia. Thin horizontal striae cover the basal portion of the metapleuron. The petiole is barely wider than the postpetiole in profile and has a well-defined subpeduncular tooth.

S. nigella is similar to Solenopsis andina and Solenopsis gensterblumi. Solenopsis nigella is just under 2.00 mm in total length while S. gensterblumi is 1.50 mm and S. andina is 2.70 mm. Additionally, S. nigella has fewer ommatidia (30- 35) than S. andina, which has 45-55 and S. gensterblumi'' has 25-30.

We agree with the synonymy of Solenopsis prevalens with S. gensterblumi (Creighton 1930). Solenopsis prevalens are probably minor workers of the nominal S. nigella, and S. gensterblumi is probably the minor and smaller major of the S. nigella. Therefore, Solenopsis nigella is probably polymorphic and probably includes S. prevalens and S. gensterblumi but with the little evidence (incomplete series) we will retain them as separate species. However, if and when a complete series is collected, these three species may be synonymized.


 * Key to New World Solenopsis Species Complexes

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

Castes
Males have yet to be collected.

Nomenclature

 * . Solenopsis nigella Emery, 1888c: 355 (w.) BRAZIL (Rio Grande do Sul).
 * Type-material: syntype workers (number not stated).
 * Type-locality: Brazil: Rio Grande do Sul (H. von Ihering).
 * Type-depository: MSNG.
 * Forel, 1912g: 5 (q.).
 * Combination in S. (Euophthalma): Creighton, 1930b: 130.
 * Status as species: Dalla Torre, 1893: 77; von Jhering, 1894: 393; Forel, 1895b: 130; Emery, 1896g: 83 (in key); Emery, 1906c: 121; Forel, 1912g: 5; Bruch, 1914: 223; Santschi, 1916e: 378; Emery, 1922e: 200; Santschi, 1923c: 257; Borgmeier, 1927c: 105; Creighton, 1930b: 130 (redescription); Ettershank, 1966: 142; Kempf, 1972a: 238; Zolessi, et al. 1988: 4; Brandão, 1991: 379; Bolton, 1995b: 389; Pacheco & Mackay, 2013: 240 (redescription).
 * Distribution: Argentina, Brazil.

Worker
Pacheco and Mackay (2013) - Measurements (n=2). TL 1.92; HL 0.690-0.768 (0.729); HW 0.642-0.720 (0.681); EL 0.114-0.120 (0.117); ED 0.078; SL 0.384; FSL 0.150-0.156 (0.153); CI 93.0-93.8 (93.4); SI 50.0-55.7 (52.8); PL 0.096-0.102 (0.099); PW 0.162; PI 59.3-62.9 (61.1); PPL 0.126; PPW 0.198; PPI 63.6; WL 0.420-0.480 (0.450); PSL 0.024-0.030 (0.027); PSW 0.018.

Concolorous golden brown; shiny sculpture; head relative large, nearly as wide as long, with vertical striae on frontal lobes and anterior of head; lateral teeth well defined, extralateral teeth absent; clypeal carinae well developed; scape, short, thin, barely exceeding midpoint of head; eye large, 30-35 ommatidia; notopropodeal suture well depressed, groove deep, separating sculpture of mesosoma, sharply defining propodeum; thin horizontal striae cover metapleuron basally; petiole nearly equal in size to postpetiole viewed laterally; subpeduncular process with well-defined tooth.

Very few hairs present with suberect and appressed hairs scattered on all body surfaces.

References based on Global Ant Biodiversity Informatics

 * Brandao, C.R.F. 1991. Adendos ao catalogo abreviado das formigas da regiao neotropical (Hymenoptera: Formicidae). Rev. Bras. Entomol. 35: 319-412.
 * Bruch C. 1914. Catálogo sistemático de los formícidos argentinos. Revista del Museo de La Plata 19: 211-234.
 * Creighton W. S. 1930. The New World species of the genus Solenopsis (Hymenop. Formicidae). Proceedings of the American Academy of Arts and Sciences 66: 39-151.
 * Cuezzo, F. 1998. Formicidae. Chapter 42 in Morrone J.J., and S. Coscaron (dirs) Biodiversidad de artropodos argentinos: una perspectiva biotaxonomica Ediciones Sur, La Plata. Pages 452-462.
 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Emery C. 1906. Studi sulle formiche della fauna neotropica. XXVI. Bullettino della Società Entomologica Italiana 37: 107-194.
 * Fernández, F. and S. Sendoya. 2004. Lista de las hormigas neotropicales. Biota Colombiana Volume 5, Number 1.
 * Forel A. 1912. Formicides néotropiques. Part IV. 3me sous-famille Myrmicinae Lep. (suite). Mémoires de la Société Entomologique de Belgique. 20: 1-32.
 * Kempf, W.W. 1972. Catalago abreviado das formigas da regiao Neotropical (Hym. Formicidae) Studia Entomologica 15(1-4).
 * Kusnezov N. 1978. Hormigas argentinas: clave para su identificación. Miscelánea. Instituto Miguel Lillo 61:1-147 + 28 pl.
 * Zolessi L. C. de, Y. P. Abenante, and M. E. de Philippi. 1988. Lista sistematica de las especies de Formicidos del Uruguay. Comun. Zool. Mus. Hist. Nat. Montev. 11: 1-9.
 * Zolessi L. C. de; Y. P. de Abenante, and M. E. Philippi. 1989. Catálogo sistemático de las especies de Formícidos del Uruguay (Hymenoptera: Formicidae). Montevideo: ORCYT Unesco, 40 + ix pp.
 * de Zolessi, L.C., Y.P. de Abenante and M.E. Philippi. 1987. Lista sistemática de las especies de formícidos del Uruguay. Comunicaciones Zoologicas del Museo de Historia Natural de Montevideo 11(165):1-9
 * de Zolessi, L.C., Y.P. de Abenante and M.E. Phillipi. 1989. Catalago Systematico de las Especies de Formicidos del Uruguay (Hymenoptera: Formicidae). Oficina Regional de Ciencia y Technologia de la Unesco para America Latina y el Caribe- ORCYT. Montevideo, Uruguay