Odontomachus desertorum Wheeler 1915, STAT. NOV.
Creators: name: Macgown, Joe A.
name: Boudinot, Brendon
name: Deyrup, Mark
name: Sorger, D. Magdalena
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hymenoptera
Formicidae
Odontomachus
Odontomachus desertorum

description: Odontomachus desertorum Wheeler, 1915 STAT. NOV.
(Figs. 6, 10, 16, 17, 24, 25, 26)
Odontomachus haematoda desertorum Wheeler, 1915: 391 Lectotype worker (here designated): United States, Arizona: Tucson, 24 November 1910 (W.M. Wheeler) [MCZC, MCZT_20523] (examined). Junior synonym of O. clarus: Brown, 1976: 103. See also: Smith, 1939. New Status.
Diagnosis. Workers of Odontomachus desertorum can be separated from the introduced species O. haematodus and O. ruginodis by the smooth, mostly unsculptured petiole (striate in O. haematodus and O. ruginodis); from O. brunneus by coarse and somewhat sparse gastral pubescence (densely pubescent in O. brunneus); and from O. 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 O. 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. 6 C) (may be nublike or well differentiated in O. clarus), the entirely striate propleurae (Fig. 6 A), 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; and 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 (Fig. 24 C), the less strongly-sclerotized digitus, and by the longer, slightly upturned, anteroventral valviceps process with rounded apex (Fig. 25 I).
Description. Worker: HL 2.59–2.74, HW 2.00–2.17, SL 2.30–2.40, EL 0.46–0.49, ML 1.45–1.57, WL 3.41– 3.57, PTH 1.33–1.35, PTL 0.59–0.60 (n=2). Entire body generally shiny except where obscured by dense pubescence; head, mesosoma, and petiole deep red, legs and antennae ferrugineous, nearly orange, and gaster piceous black. Head with fine, longitudinal striae covering much of the head in full-face view, striae beginning on frontal lobes and clypeus and diverging toward posterior corners of head, fading at corners and sides; sides and underside of head smooth with fine piligerous punctures; head with fine appressed pubescence and with sparse, variable setae present on postgenal bridge and in ocellar triangle. Pronotum with circular, concentric striae which are transverse along rear margin; appressed pubescence abundant; 0–4 elongate erect setae present. Mesonotum and propodeum with transverse striae, striae coarser on propodeum; propleuron entirely striate; mesopleuron striate in dorsal fifth and near mesocoxae; basalar lobe smooth; pubescence abundant on mesonotum and propodeum. Metasternum lacking paired elongate, spiniform processes between hind coxae. Petiole in profile view widest at base and tapering gradually toward posterodorsally-directed spine; petiole, in anterior view, with dorsomedian process thick at base, long, and poorly differentiated; node mostly smooth and shining, with weak striae present near base; subpetiolar process rounded, triangular; appressed pubescence present anteriorly and laterally, but mostly absent posteriorly. Gaster mostly smooth and shining, although faintly coriacious dorsomedially; fine appressed pubescence somewhat sparse, hairs separated by somewhat less than one hair length; scattered standing setae present.
Male: HL 0.97–1.06, HW 1.34–1.37, SL 0.23–0.25, EL 0.69–0.75, EW 0.43–0.44, OL 0.18; OES 0.21–0.26, WL 2.61–3.06, PTH 0.87–0.94, PTL 0.54–0.82, FWL 5.32–5.64 (n=2). Body generally shiny except where obscured by dense pubescence; head and appendages honey yellow, mesosoma and metasoma light golden brown. Head and body with dense pubescence of variable stature. Eyes extremely large, maximum diameter of each eye at least 70% of head length in full-face view. Ocelli relatively large but not hypertrophied, the length of each ocellus slightly more than half the distance between lateral ocellus and eye margin; in full-face view, lateral ocelli protrude beyond posterior margin of head. Mesosoma: pronotum coriaceous to granulose; mesoscutum covered with weakly rugose striae which are transversely arcuate anteriorly and becoming longitudinal posteriorly; mesoscutellum raised and convex, with longitudinal striae; mesopleuron roughened by dense, weak sculpture; propodeum finely striate. Petiole bluntly rounded apically, with digitate subpetiolar process; densely pubescent anteriorly and laterally, with reduced pubescence posteriorly. Abdominal sternum IX disc trapezoidal, breadth about twice length; posterior lobe length almost three times maximum width, basal half barely narrowed. Telomeral apex narrowly rounded; telomere length distinctly greater than height; valviceps ventral apex strongly produced and very narrow; apical margin of valviceps linear before weakly and abruptly curving posteriorly at apicoventral process; anteroventral process of valviceps slightly elongated, with a rounded, slightly upturned apex; vertical portion of dorsolateral carina and lateral margin of subapical lamina curving into one another; apicodorsal lobe of valviceps narrow and elongated; subapical lamina broad.
Distribution (Fig. 26, Appendix 1). Sonoran Desert. USA. Arizona: Maricopa and Pima Counties. Mexico. Sonora. Distributional information from specimens examined from LACM, MCZC, and UCDC.
Discussion. 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. 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.
New worker-based characters for separating O. desertorum from O. clarus are the former’s longer antennal scapes (see diagnosis), shorter cervical pronotal lobe (which contacts the occiput when the head is reflexed), and entirely or almost entirely striate propleurae (which forms the longitudinally divided area beneath the pronotum and above the procoxae, and is technically the proepisterna) (Fig. 6 A). The male of O. desertorum is conspicuously different from that of O. clarus in terms of coloration and with respect to the petiolar sternum, which is strongly angled in O. desertorum (Fig. 10 A) and nearly flat in O. clarus (Fig. 10 B). Genitalic differences between the two species are indicated in the diagnosis above. The ocelli of male O. desertorum are also slightly larger than O. clarus; this may reflect a more light-restricted flight timing or perhaps size-based allometry. Until further males are collected and phenological data are recorded and collated, it is too early to infer temporal isolation of diel flight times between the two species. Beyond worker and male morphology, little is known about the biology of O. desertorum. Whereas O. clarus is usually collected in woodland habitats, O. desertorum seems to prefer open desert/desert-scrub habitats. Smith (1939) noted that O. desertorum may be common but infrequently collected due to nocturnal or matinal foraging times. Material provided by Stefan Cover (MCZ) suggest that this may indeed be true, as the label data indicate that the workers were collected while “nocturnal[ly] foraging.
description: Published as part of Macgown, Joe A., Boudinot, Brendon, Deyrup, Mark & Sorger, D. Magdalena, 2014, A review of the Nearctic Odontomachus (Hymenoptera: Formicidae: Ponerinae) with a treatment of the males, pp. 515-552 in Zootaxa 3802 (4) on pages 533-536, DOI: 10.11646/zootaxa.3802.4.6, http://zenodo.org/record/249896