Solenopsis tonsa

Thompson (1989) - This species may not be rare, but merely previously unrecognized. Virtually nothing is known about tonsa biology. I have never collected sexuals of this species. I suspect that mating flights occur in late summer since the two females in my possession are fully sclerotized, have wings and bear the dates 15 August (swept from a soybean field) and 2 July (nest collected). They are probably day flyers since I have never taken them in light traps. Pacheco and Mackay (2013) report collecting this ant 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.

Thompson (1989) - Workers pale yellow and densely covered with short hairs. Head strongly marked with prominent punctures but with a clear median strip free of punctures and hairs. Eyes pale and small. Most similar to pergandei and tennesseensis, but hairs on thorax are as dense as on the head and all of the same length, not of various lengths or longer than those on the head. Although similar to tennesseensis in having a median hair-free strip on the head, tonsa is much larger and does not have the long flat head of tenesseensis.

Queen large and dark with hyaline wings. Head distinctly trapezoidal in shape. Head and dorsum of thorax covered with numerous strong piligerous punctures. Most similar to nickersoni but its non-rectanular head and larger size set it apart from nickersoni and picta while the hyaline wings separate it from both tenesseensis and nickersoni. Largest dark female among the Florida species.

Male dark reddish brown with hyaline wings. Head distinctly trapezoidal with the greatest width across the eyes. Legs, mandibles and chitinous areas near mouthparts are whitish to light tan. Most similar to abdita, but distinguished by nondusky wings, blunt knobs on the dorsum of the petiole and gradual color shading on the thorax. Largest dark male among the Florida species.

Curiously, the dense pilosity of this species led to its discovery. I noticed that workers in certain vials had many more dirt granules trapped in their hairs-which prompted a closer look and the new species discovery. This ant looks very much like a golden-haired pincushion under the microscope. This character was not used in the key, however, because of the perennial problems associated with the description of hair characteristics.

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.


 * Key to New World Solenopsis Species Complexes

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
HL 0.31-0.39; HW 0.32-0.34; HI 83-94; SL 0.22-0.24; SI 65; EL 0.02; WL 0.42-0.46. (N = 9 from Alachua Co.).

Structural Characters—Head longer than wide, rectanguloid with faintly convex sides, the posterior border slightly excised in the center. The head is slightly narrower anteriorly. The eyes are very small compared to most Florida species and are often hard to locate because eye coloration is the same as, or only slightly darker than, the head. Ventral border of head moderately convex in profile. Anterior edge of clypeus widely and angularly separated from dorsal surface of mandible in profile.

Promesonotum of thorax weakly convex in profile, propodeal base somewhat more convex. Petiole large in profile with a prominent anteroventral tooth and prominent ventral swelling. From above, petiole and postpetiole nearly equal in width. Postpetiole with rounded sides as seen from above, not trapezoidal.

Sculpture—All surfaces smooth and shining except for head which is heavily and densely marked with prominent piligerous punctures and dorsum of the promesonotum which is moderately marked with weaker punctures. Head has characteristic median streak free of punctures.

Pilosity—Head and thorax with numerous short hairs. Petiole, postpetiole, legs and gaster also with numerous short hairs which may be longer than those on the head.

Color—Entirely light yellow to light yellowish brown.

Pacheco and Mackay (2013) - (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.

Queen
HL 0.72; HW 0.76-0.77; HI 106, SL 0.42-0.44; SI 59.4; EL 0.22-0.24; WL 1.44-1.46 (N = 2 from Leon and Alachua Counties).

Structural Characters—Head distinctly trapezoidal, with nearly straight sides and hind border, sides of head distinctly convergent toward the clypeus. Scapes short, not reaching hind corners of head. Sublateral clypeal teeth easily seen beside each of the two more prominent submedian teeth.

Thorax slightly narrower than head. The sides of the scutum, from above, narrow posteriorly in nearly straight lines; the transcutal suture V -shaped. Petiole with blunt node, slightly excised above as seen from behind. Petiole, in profile, with a small posterior ventral tooth. Postpetiole wider than petiole and trapezoidal as seen from above, wider posteriorly.

Sculpture—All body parts smooth and shining except postpetiole and sides of petiole, which are covered with very fine granular punctation.

Pilosity—Head and thorax with numerous hairs arising from strong punctures. Gastric pilosity also abundant but arising from less prominent punctures.

Color—Head including mandibles, thorax, petiole, postpetiole and gaster dark reddish brown, shading to lighter tones on ventral surfaces. Legs and antennae light brownish yellow. Wings hyaline.

Male
HL 039-0.42; HW 0.52-0.56; HI 132-135; FL 0.86-0.92; EL 0.22-0.24; WL 1.18-1.26 (N = 4 from Leon Co.).

Structural Characters—Head trapezoidal, seen from above, and widest at the eyes. Ocelli prominent. Eyes occupy approximately 114 of total head width. Eyes longer than broad, narrowed and flattened toward top of the head.

Thorax, from above, tapers smoothly from pronotum to propodeum. Petiole with 2 triangular rounded knobs, one at each corner of the dorsum. Petiole narrower than postpetiole. Postpetiole from above nearly circular but flattened on the anterior face.

Sculpture—Entire propodeum, sides of petiole and post petiole and sclerites surrounding the wings covered with granulose punctation. Remainder of body smooth and shining.

Pilosity—Suberect clear hairs most prominent on dorsal body surfaces, particularly the thorax, but also on head, petiole and terminal segments of gaster.

Color—Body dark reddish brown. Thorax shades from dark brown dorsally to medium brown pleurites to light brown ventrally. Legs and antennae cream colored, shading to light brown on coxae and basal antenna! segments. Wings hyaline.

Type Material
Holotype is a worker from Tall Timbers Research Station, Leon Co., Florida, collected June 1975 by M.A. Naves. Paratypes are remainder of the Leon Co. series including 2 females, 4 males and 3 workers. Additional paratype material includes numerous workers from Gainesville Airport area, Alachua Co., Florida, 16 June 1979, captured with baited subterranean trap by C. R. Thompson. The holotype and several paratypes will be deposited in the Florida State Collection of Arthopods, Gainesville, Florida. Paratypes will also be deposited in and Los Angeles County Museum of Natural History.

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.

Etymology
The word “tonsa” is Latin for “shaven” and is dubbed upon this species because of the distinctive hairless vertical strip down the center of the worker's head

References based on Global Ant Biodiversity Informatics

 * Deyrup, M. 2003. An updated list of Florida ants (Hymenoptera: Formicidae). Florida Entomologist 86(1):43-48.
 * Forster J.A. 2005. The Ants (hymenoptera: Formicidae) of Alabama. Master of Science, Auburn University. 242 pages.
 * MacGown J. A., J. G. Hill, and R. L. Brown. 2010.  Native and exotic ant in Mississippi state parks.  Proceedings:  Imported Fire Ant Conference, Charleston, South Carolina, March 24-26, 2008: 74-80.
 * MacGown, J.A and J.A. Forster. 2005. A preliminary list of the ants (Hymenoptera: Formicidae) of Alabama, U.S.A. Entomological News 116(2):61-74
 * Oyama L., J. R. King, and D. G. Jenkins. 2018. Diversity and distribution of Solenopsis (Hymenoptera: Formicidae) thief ants belowground. Myrmecological News 27: 47-57.
 * Spiesman B. J. and G. S. Cumming. 2008. Communities in context: the influences of multiscale environmental variation on local ant community structure. Landscape Ecol. 23: 313-325
 * Thompson C. R. 1989. The thief ants, Solenopsis molesta group, of Florida (Hymenoptera: Formicidae). Florida Entomologist 72: 268-283