Solenopsis tonsa

Thompson (1982) states that nothing is known of the biology of S. tonsa. We collected it (Pacheco and Mackay 2013) in subterranean Vienna sausage baits at 1500 feet elevation in light brown moist sandy soils in a forest in Texas.

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

Pacheco and Mackay (2013) – Worker - This species is easily recognized as having an elongate, yet robust and ventrally concave head, which is densely hairy and coarsely punctate. The eyes are minute, with about one ommatidium. The body is densely pilose and covered in erect and suberect hairs. The petiole is robust with a small peduncular tooth ventrally.

Solenopsis tonsa is similar to Solenopsis subterranea and may be confused as both species have densely hairy bodies. Solenopsis tonsa is easily separated by its robust, thickened head viewed laterally compared to the more slender head of S. subterranea. Additionally, the petiole of S. tonsa is much more robust with a small tooth present at the subpeduncular process; absent in S. subterranea. The distributions probably overlap in Texas.

Distribution based on Regional Taxon Lists
Nearctic Region: United States.

Nomenclature

 *  tonsa. Solenopsis tonsa Thompson, 1989: 272, figs. 29-32 (w.q.m.) U.S.A.

Pacheco and Mackay (2013) - Dr. Trager suggests what we consider to be S. tonsa may not be conspecific with the real S. tonsa, as our specimens have hairs over the surface of the head and S. tonsa has a non pilose medial strip on the head.

Worker
Pacheco and Mackay (2013) - Measurements (n=5). TL 1.38-1.74 (1.56); HL 0.390-0.402 (0.398); HW 0.312-0.348 (0.331); EL 0.024-0.030 (0.025); ED 0.024; SL 0.240-0.252 (0.242); FSL 0.078-0.084 (0.083); CI 78.8-86.6 (83.1); SI 59.7-62.7 (60.8); PL 0.078-0.084 (0.083); PW 0.096-0.120 (0.112); PI 65.0-87.5 (74.9); PPL 0.108-0.120 (0.110); PPW 0.114-0.120 (0.119); PPI 90.0-100.0 (92.9); WL 0.300-0.312 (0.305); PSL 0.024-0.030 (0.026); PSW 0.024.

Concolorous pale yellow; head elongate, ventrally concave; lateral clypeal teeth sharp, extralateral teeth absent; clypeal carinae well developed; scape short, extends 2/3 length to posterolateral corner of head; eyes small, circular, with about one ommatidium; notopropodeal suture weakly depressed; propodeal spiracle small; posterior propodeal margin rounded, only slightly angulate; petiole slightly wider than postpetiole viewed dorsally; petiolar peduncle with small ventral tooth.

Abundantly pilose; head, mesosoma and gaster covered with short (0.020 mm) erect and suberect hairs equal in length; head densely hairy except for narrow central strip.

Type Material
Pacheco and Mackay (2013) - We were not able to locate the types of S. tonsa in any of the museums where they were reportedly deposited by Thompson (1989), as they were borrowed by Thompson in 1989 (S. Cover and M. Deyrup, pers. comm.). A series of specimens collected from Texas was identified as S. tonsa (based on Thompson's description and figures) as our only alternative.