Odontomachus desertorum

Identification Keys including this Taxon

 * Key to US Odontomachus species

Workers of Odontomachus desertorum can be separated from the introduced species Odontomachus haematodus and Odontomachus ruginodis by the smooth, mostly unsculptured petiole (striate in O. haematodus and O. ruginodis); from Odontomachus brunneus by coarse and somewhat sparse gastral pubescence (densely pubescent in O. brunneus); and from Odontomachus relictus by the smooth basilar lobes (striate in O. relictus). Additionally, O. desertorum can be separated from these species by geography as it is restricted to the Sonoran Desert region of the southwestern US and northwestern Mexico; whereas, all of the aforementioned species are only known to occur east of the Mississippi River in the US.

Workers of O. desertorum are most similar to those of Odontomachus clarus (also a western species), with workers of both species being similar in coloration, having coarse gastric pubescence and a smooth petiole and basalar lobe, but may be differentiated from O. clarus by the much larger size (WL 3.41– 3.57 compared to WL 2.43–2.83 for O. clarus), stout, poorly differentiated dorsomedian petiolar spine (Fig. 6C) (may be nublike or well differentiated in O. clarus), the entirely striate propleurae, pronotal cervical lobes which are wider than long, and by the relatively longer scapes (SL/HW = 1.11–1.15 vs. 0.99–1.07).

Males are uniquely identifiable among US species by the following character combination:
 * 1) generally large size (WL 2.61–3.06)
 * 2) ocelli relatively large and bulging beyond posterior border of head
 * 3) body light golden brown and appendages honey yellow
 * 4) propodeum finely striate
 * 5) petiolar sternum posteriorly glabrous and with a distinct angular process near the posterior margin

The genitalia of O. desertorum are most similar to O. clarus from which they differ mainly by the narrower posterior ninth sternal lobe, the less strongly-sclerotized digitus, and by the longer, slightly upturned, anteroventral valviceps process with rounded apex.

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

Biology
Odontomachus desertorum is restricted to the Sonoran Desert; its range in Arizona is surrounded by that of O. clarus to the north, east, and south.

Nomenclature

 *  desertorum. Odontomachus haematoda subsp. desertorum Wheeler, W.M. 1915b: 391 (w.) U.S.A. Junior synonym of clarus: Brown, 1976a: 103. Revived from synonymy and raised to species: MacGown et al., 2014: 533. See also: Smith, M.R. 1939d: 128.

Taxonomic Notes
When first described as a subspecies of O. haematodus ("haematoda") by Wheeler (1915), the coloration and petiolar node form were used to characterize the taxon, a character set scarcely improved by M.R. Smith (1939) who noted the larger size and well-developed lateral ocellar pits of O. desertorum. Creighton (1950) repeated this diagnosis in his derivative key to the North American Odontomachus. Brown (1976) synonymized O. haematodus desertorum with O. clarus, but unfortunately did not provide support for this action. Based on the discovery and examination of the male of O. desertorum and a reassessment of worker variation for names attributable to O. clarus, it is here determined that O. desertorum should be revived from synonymy and elevated to species. While no sympatric material of O. desertorum and O. clarus were examined during this study, M.R. Smith (1939) indicated that the two species may occur within a few miles of one another, supporting recognition of O. desertorum as a valid species.

References based on Global Ant Biodiversity Informatics

 * Johnson R. Personnal Database. Accessed on February 5th 2014 at http://www.asu.edu/clas/sirgtools/resources.htm
 * MacGown J. A., B. Boudinot, M. Deyrup, and D. M. Sorger. 2014. A review of the Nearctic Odontomachus (Hymenoptera: Formicidae: Ponerinae) with a treatment of the males. Zootaxa 3802(4): 515-552.