Mycetomoellerius turrifex

Identification
Trachymyrmex turrifex is distinguished from other North American species by its well-developed antennal scrobes. Only the allopatric Trachymyrmex jamaicensis has comparably developed antennal scrobes, but it may be easily distinguished from T. turrifex by its larger size, reddish-black coloration and shorter clypeal pilosity. (Rabeling et al. 2007)

Distribution
The geographic range of T. turrifex is centered in Texas and extends into southern Oklahoma, western Louisiana, and south into the Mexican States of Chihuahua and Tamaulipas. (Rabeling et al. 2007)

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

Habitat
T. turrifex is abundant in open desert habitats of west Texas, the black clay soils of central Texas and is somewhat less abundant in the sandy soils of eastern Texas and western Louisiana. (Rabeling et al. 2007)

Biology
From Rabeling et al. (2007): Dense populations occur in southern Texas, particularly in the Rio Grande Valley. When occurring sympatrically in sandy soils with Trachymyrmex septentrionalis, T. turrifex is less abundant, but the reverse pattern occurs in black clay soils where turrifex is usually more common than septentrionalis. The characteristic turret like nest entrances, which are built from soil particles and plant litter debris during the wetter parts of the year, are a diagnostic character for turrifex in the field. Turrets are absent during winter dormancy and are reduced or absent in summer, particularly after a period of drought. Nests consist of 1–5 chambers, which are connected by vertical tunnels. Colonies are monogynous and contain up to 300 workers.

Nomenclature

 *  turrifex. Atta (Trachymyrmex) turrifex Wheeler, W.M. 1903b: 100, fig. 6 (w.q.) U.S.A. Combination in Trachymyrmex: Gallardo, 1916b: 242. Senior synonym of caroli: Rabeling, Cover, et al. 2007: 23.
 * caroli. Atta (Trachymyrmex) turrifex subsp. caroli Wheeler, W.M. 1911g: 248 (w.) U.S.A. Combination in Trachymyrmex: Creighton, 1950a: 324. Junior synonym of turrifex: Rabeling, Cover, et al. 2007: 23.

Trachymyrmex turrifex is distributed throughout Texas, northeastern Mexico, western Louisiana, and rarely reaches southern Oklahoma. Individuals are somewhat variable in size, and color varies from light yellowish brown to dark reddish-brown. Wheeler (1903) described turrifex from several localities in Central Texas, and T. turrifex caroli as a subspecies of T. turrifex from Huntsville, Texas (1911). Wheeler’s reasoning was that caroli “represents a depauperate, arenicolous race ranging considerably eastwards of the typical turrifex” (Wheeler 1911, p. 248). Wheeler distinguished between these two “subspecies” based on the smaller ody size, brownish yellow coloration, smaller tubercles, and lack of longitudinal impression on first gastric tergite in T. turrifex caroli. In our experience, all of these character states fall well within the variation observed within and among colonies of typical turrifex, as seen throughout its known geographic range, which now extends to western Louisiana and places Huntsville towards the center of T. turrifex’s distribution. Since we were not able to locate Wheeler’s type specimens of T. turrifex caroli, we collected fresh material at the type locality in Huntsville, Texas. These specimens were morphologically not different from other examined turrifex. Lastly, our DNA sequence information indicates that caroli is also genetically not distinct from turrifex. We therefore synonymize T. turrifex caroli with T. turrifex. (Rabeling et al. 2007)

Worker
Diagnosis from Rabeling et al. (2007): HL 0.88–1.0, HW 0.8–0.96, CI 91–96, SL 0.72–0.8, SI 83–91, ML 1.2–1.4. A medium sized, species (HL 0.88–1.0, HW 0.8–0.96) with the shortest antennal scapes (SI 83–91) relative to head width of all US Trachymyrmex species. The scapes reach or pass the posterior corner of the head by half its maximum diameter at most. Head slightly longer than broad (CI 91–96) with its maximum width close to the posterior border of head, tapering gradually from point of broadest width to mandibular insertion. Posterior margin moderately concave. Both preocular and frontal carinae long and subparallel, reaching back towards the posterior margin of head, forming well-developed antennal scrobes. In full face view, frontal lobes broad, rounded, describing a half circle. Anterolateral promesonotal teeth short, thin, in dorsal view sharply pointed, directed anterolaterally and upwards. Bases of median pronotal teeth fused, but the peaks of each tooth still distinguishable. Propodeal teeth pointed, almost twice as long as the distance between their bases. Dorsal body surface strongly tuberculate, tuberculi well developed, on first gastric tergite, sometimes connected through ridges. Tuberculi bearing long, dark, strongly recurved setae. Side of mesosoma less tuberculate, tuberculi smaller. Color is variable from yellowish brown to medium reddish brown.

Queen
Diagnosis from Rabeling et al. (2007): HL 1.1–1.2, HW 1.1–1.2, CI 100, SL 0.85–1.0, SI 71–87, ML 1.7–1.8. As in the worker diagnosis, except for case-specific structures of the mesosoma related to wing-bearing. Dorsoventral pronotal teeth pointed, broadly triangular in dorsal view; ventrolateral pronotal teeth small, lobelike. Mesoscutum with moderately abundant, short, coarse, longitudinal rugulae and abundant small tuberculi, each bearing a stiff, more or less recurved suberect or decumbent seta. Rear border of scutellum projecting posteriorly as two lobelike teeth. First gastric tergite covered with small tubercles interconnected by a network of fine rugulae forming an almost geometric pattern; each tubercle bearing a stiff, recurved, decumbent setae.

Male
Diagnosis from Rabeling et al. (2007): HL 0.7–0.75, HW 0.6, CI 80–86, SL 0.7–0.75, SI 117–125, ML 1.5–1.6. A distinctive Trachymyrmex male easily recognized by the general lack of tuberculi on all body surfaces. In addition, the rear border of the antennal scrobe is poorly defined or absent. Dorsoventral pronotal teeth small, triangular, usually sharply pointed; ventrolateral pronotal teeth absent. Mesoscutum sparsely to moderately longitudinally rugulose, interrugal spaces finely granulate. In dorsal view, rear border of scutellum forming two triangular teeth that project posteriorly. First gastric tergite finely granulate with scattered punctures bearing fine, appressed recurved setae.

Type Material
Syntype workers and queens, ,. Examined (Rabeling et al. 2007).

Type Locality Information
Marfa, Presidio County; Fort Stockton, Pecos County; Del Rio and Langtry, Valverde County; Marble Falls, Burnet County; Austin, Travis County; Texas, U.S.A. (Rabeling et al. 2007).

Etymology
The epithet for T. turrifex is derived from its characteristic turretlike nest entrances, which are built from soil particles and leaf litter debris. (Rabeling et al. 2007).

Additional References

 * Rabeling, C., S. P. Cover, R. A. Johnson, and U. G. Mueller. 2007. A review of the North American species of the fungus-gardening ant genus Trachymyrmex (Hymenoptera : Formicidae). Zootaxa.1-53.


 * Wheeler, W. M. (1911) Two fungus-growing ants from Arizona. Psyche, 18, 93-111.