Atta versicolor chisosensis

Identification
A number of workers taken by Judge O.W.Williams in the Chisos Mountains of southwestern Texas, and a few workers taken by William Morton Wheeler at Terlingua in the same region represent a distinct subspecies.

They differ from the typical versicolor in their distinctly lighter and more yellowish color, much less pronounced sculpture and in having only a few (about 12) pointed tubercles on each side of the median gastric depression, whereas in the typical form there are two or three times as many. Owing to their feebler sculpture the workers of chisosensis are throughout much more shining than the typical form.

Medial pronotal spine well developed and with an acute inclination, oriented anteriorly. Eyes small, convex and salient. Propodeal spine much longer than its basal width.

Workers uniform with respect to thoracic spination, irrespective of size. In smaller workers, there is a tendency toward a reduction of the tuberculation of the 3rd gastric segment, and the  two species are not distinguishable is small workers are used. The propodeal spines are well developed in workers of all sizes, but the thoracic spines tend to reduce in smaller workers.

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



Biology
This species is probably the most xeric adapted of the subgenus Moellarius. It is apparently unique in that it heavily cuts xeric dicotyledonous plants.

Nomenclature

 * chisosensis. Atta (Moellerius) versicolor subsp. chisosensis Wheeler, W.M. 1907c: 705 (w.) U.S.A.
 * Combination in Acromyrmex: Emery, 1924d: 351.
 * Combination in Acromyrmex (Moellerius): Fowler, 1988: 291.
 * Junior synonym of versicolor: Shattuck & Cover, 2016: 11.