Solenopsis isopilis

Known only from the types (Veracruz, Mexico). These were collected in a selva mediana subperennifolia (medium, sub perennial rain forest) in a subterranean sample trap.

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

Pacheco and Mackay (2013) - Worker - The workers are small and yellowish-brown with an elongate head, which is covered with coarse punctures. The erect hairs on the dorsum of the head and dorsum of the gaster are about equal in length and are usually very dense, especially on the dorsum of the gaster. The eye is small and the same color as the remainder of the head, but is well defined, although individual ommatidia cannot be distinguished. The minor segments of the funiculus are short, in total only slightly longer than the shortest segment of the antennal club. The gaster is noticeably long compared to the mesosoma.

The erect hairs of equal lengths on the dorsum of the gaster would separate this species from most of the others of the pygmaea complex, except for Solenopsis minutissima (Argentina), Solenopsis pygmaea (Mexico and Caribbean) and Solenopsis subterranea (southern USA to northern South America). It can be easily separated from S. pygmaea and S. subterranea by having few erect hairs on the dorsum of the propodeum (when viewed in profile). The well-defined eyes would separate it from S. minutissima.

Distribution
Veracruz, Mexico.

Distribution based on Regional Taxon Lists
Neotropical Region: Mexico.

Castes
Known only from the worker caste.

Nomenclature

 *  isopilis. Solenopsis isopilis Pacheco & Mackay, 2013: 188, figs. 128-129, map 29 (w.) MEXICO.

Worker
Measurements (n=6). TL 0.960-1.08 (1.05); HL 0.300-0.318 (0.312); HW 0.228-0.240 (0.232); EL 0.012-0.018 (0.017); ED 0.012-0.018 (0.017); SL 0.156-0.174 (0.165); FSL 0.060-0.066 (0.061); CI 71.7-78.4 (74.4); SI 50.9-56.0 (52.9); PL 0.060-0.072 (0.065); PW 0.066-0.078 (0.071); PI 90.9-92.3 (91.5); PPL 0.072-0.078 (0.075); PPW 0.078-0.084 (0.081); PPI 92.3-92.9 (92.6); WL 0.204-0.210 (0.209); PSL 0.012; PSW 0.012.

Small, concolorous yellowish-brown; all surfaces with glossy appearance, head and mesosoma with scattered, coarse punctures; head elongate, posterior margin slightly concave, covered with coarse punctures; clypeal carinae and lateral teeth well developed; eye small, same color as remainder of head, but well defined; minor segments of funiculus short, only slightly longer than shortest segment of antennal club; scape extends slightly more than half distance to posterior lateral corners of head; mesopleuron and metapleuron smooth and glossy; posterior propodeal margin rounded, spiracle small; petiole wider than postpetiole when viewed laterally; gaster elongated.

Erect hairs on dorsum of head and gaster approximately equal in length, usually very dense, especially on dorsum of gaster; erect hairs on dorsum of head abundant (0.020 mm in length), nearly equal in length, pronotum with approximately 10 erect hairs (0.030 mm in length), hairs on remainder of mesosoma, petiole and postpetiole similar, erect hairs on dorsum of gaster approximately equal in length (0.020 mm).

Type Material
Holotype worker and 15 paratype workers (, IEMJ,, MCZC, ), Mexico, Res. Ecol. "La Mancha", junio 1991, Col. P. Rojas.

Etymology
From Greek, isos, meaning equal and pilos meaning hair, referring to the numerous hairs on the gaster, which are equal in length.