Solenopsis pygmaea

Solenopsis pygmaea nests underground and was collected in soil in Selva Avacohite. This species was collected in tropical rain forest by subterranean baits at 11 m in elevation in clay and 69 m in elevation in rocky loam soil in Guatemala.

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

Pacheco and Mackay (2013) – Worker - The workers are small (usually less than 1.00 mm in total length), pale yellow ants, in which the minor segments of the funiculus are short in total length. The lateral clypeal teeth are well developed and the extralateral teeth are absent. The punctures on the head are moderately large, larger than the hairs that arise from them. Queen - The queen is large (about 5 mm total length). It is medium brown with a lighter brown gaster (due in part to the lighter intersegmental membranes of the distended gaster) to black. The eye is relatively small (maximum diameter 0.180 mm), extending about 1/3 of the length of the side of the head. The dorsum of the head is covered with coarse punctures. The scapes and tibiae are covered with suberect hairs. Both the petiole and postpetiole are thickened, robust and have rugulae.

The workers of this species are nearly identical to those of Solenopsis tennesseensis, differing in being slightly smaller and more abundantly covered with erect hairs. The hairs on the dorsum of the first tergum are all short (up to 0.030 mm, few up to 0.040 mm), abundant (more than 20) and approximately equal in length. The similar hairs of S. tennesseensis are longer (many 0.050 mm), sparse (fewer than 20) and are somewhat unequal in length. Specimens from Mexico appear to be identical to specimens from Puerto Rico, but are not associated with queens.


 * Key to New World Solenopsis Species Complexes

Distribution based on Regional Taxon Lists
Neotropical Region: Barbados, Grenada, Guadeloupe, Guatemala, Haiti, Mexico, Netherlands Antilles, Puerto Rico, Saint Vincent and the Grenadines.

Castes
Males have yet to be collected.

Nomenclature

 * exigua. Solenopsis exigua Forel, 1893g: 395 (w.) ANTILLES. Junior secondary homonym of exigua Buckley, above.] Replacement name: pygmaea: Forel, 1901e: 345.
 *  pygmaea. Solenopsis pygmaea Forel, 1901e: 345. [Originally misspelled as pygmaca; justified emendation to pygmaea by Forel, 1915c: 354.] Replacement name for exigua Forel, 1893g: 395. [Junior secondary homonym of exigua Buckley, 1867: 342.]

Worker
Pacheco and Mackay (2013) - Measurements (n=6). TL 0.960-1.08 (0.996); HL 0.342-0.360 (0.350); HW 0.240-0.276 (0.255); EL 0.018-0.030 (0.024); ED 0.012-0.024 (0.019); SL 0.204-0.222 (0.211); FSL 0.060-0.066 (0.064); CI 70.2-76.7 (72.8); SI 58.3-64.9 (60.3); PL 0.060-0.066 (0.063); PW 0.072-0.090 (0.081); PI 66.7-84.6 (78.2); PPL 0.078-0.090 (0.082); PPW 0.102-0.108 (0.103); PPI 76.5-88.2 (79.6); WL 0.240-0.360 (0.260); PSL 0.018-0.030 (0.024); PSW 0.018-0.024 (0.020).

Small, concolorous pale yellow; head elongate, longer than wide, posterior border straight, semi-coarsely punctated; lateral clypeal teeth well developed, extralateral teeth absent; clypeal carinae weakly defined, nearly absent; scape does not reach posterior border of head; minor segments of funiculus 3-8 short, less than 0.070 mm total length; eyes small, 1-3 ommatidia; pronotum coarsely punctate, smooth and shiny between punctures; mesopleuron smooth and shiny; metapleuron with faint, thin striae; posterior propodeal margin rounded; petiole wider than postpetiole viewed laterally; petiolar node round, somewhat triangular, lacking tooth or flange ventrally; postpetiolar node oval viewed laterally and dorsally.

Abundantly hairy; pronotum with numerous erect hairs, of different lengths; hairs on posterior tibiae usually slightly raised from cuticular surface; erect and suberect hairs on first tergum of gaster similar to those on pronotum, but tend to be equal in length (0.036 mm); hairs on remaining terga longer and coarser.

Queen
Pacheco and Mackay (2013) - Measurements (n=1). TL 4.92; HL 0.648; HW 0.600; EL 0.180; ED 0.150; MOL 0.066; MOD 0.072; SL 0.420; FSL 0.240; CI 92.6; SI 64.8; PSL 0.072; PSW 0.066; PL 0.138; PW 0.282; PI 48.9; PPL 0.180; PPW 0.324; PPI 55.6; WL 0.960.

Large, medium brown with lighter brown to black gaster; head longer than wide, coarsely punctated; clypeal lateral teeth well developed, extralateral teeth angulate; clypeal carinae weakly defined; eye relatively small, extending about 1/3 length of side of head; medial ocellus small; scape yellow, does not reach posterior border of head; minor segments of funiculus long; mesosoma, petiole, postpetiole and first gastral tergum coarsely punctated; pronotum and mesopleuron smooth and shiny between punctures; propodeum striate; petiole robust, wider than postpetiole (viewed laterally); petiole rugose, node triangular, peduncle with tooth or flange ventrally; postpetiolar node globose, lacking tooth or flange ventrally.

Abundantly hairy; erect and suberect hairs covering all body surfaces; erect hairs on pronotum nearly equal in length (~0.120 mm); scapes and tibiae covered with suberect hairs; hairs on petiole and postpetiole curve posteriorly.

Type Material
Pacheco and Mackay (2013) - (lectotype worker [here designated], Forel Coll. ), Antilles Is., St. Vincent.

References based on Global Ant Biodiversity Informatics

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 * Snelling R. R. 2005. Wasps, ants, and bees: aculeate Hymeoptera. Pp. 283-296 in: Lazell, J. 2005. Island. Fact and theory in nature. Berkeley: University of California Press, xx + 382 pp.
 * Torres, Juan A. and Roy R. Snelling. 1997. Biogeography of Puerto Rican ants: a non-equilibrium case?. Biodiversity and Conservation 6:1103-1121.
 * Wheeler W. M. 1905. The ants of the Bahamas, with a list of the known West Indian species. Bulletin of the American Museum of Natural History 21: 79-135.