Odontomachus brunneus Patton 1894
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 brunneus

description: Odontomachus brunneus (Patton, 1894)
(Figs. 4, 7, 8, 12, 13, 24, 25, 26)
Atta brunnea Patton 1894: 618 (worker) Georgia, USA.
Odontomachus brunneus (Patton, 1894); Emery, 1895: 268 (as junior synonym of Odontomachus insularis Guérin-Méneville, 1844); Brown, 1976: 103, 139 (as senior synonym of O. fuscus); Deyrup, Trager & Carlin, 1985: 191 (male). Odontomachus fuscus Stitz, 1925:115; Brown, 1976: 103, 139 (unresolved junior homonym of Odontomachus fuscus Stitz, 1916: 372).
Diagnosis. Workers of this species are distinguished from others in our region by the much finer and denser pubescence on the first gastral tergite. Males are yellow-colored and most easily confused with those of O. haematodus; those of O. brunneus are clearly separated by the following characters: 1) ocelli larger, projecting beyond the posterior border of the head; 2) metasternal processes short, not elongate and spine-like; 3) posterior face of propodeum not offset from dorsal and lateral faces by distinct carina, and by numerous genitalic characters (see Figs. 24, 25). Male O. brunneus are further separated from other US species by the transverse mesoscutal striae, and by the anteroposteriorly slender mesosoma. Genitalia of O. brunneus are most similar to those of O. ruginodis and O. clarus, but are distinguished from these two species by the following characters (see Figs. 24, 25): abdominal sternum IX narrower and longer than O. clarus, and broader than O. ruginodis; telomere apex broadly rounded, posterodorsal margin nearly linear (apex narrower and posterodorsal margin sinuate in O. clarus and O. ruginodis); valviceps apicodorsal lobe broad (narrow in O. clarus), subapical lamina narrow (broad O. clarus and O. ruginodis). Odontomachus brunneus has the proportionally shortest (dorsoventral) valviceps of the Nearctic species.
Description. Worker: HL 2.10–2.44, HW 1.58–1.92, SL 1.84–2.10, EL 0.34–0.42, ML 1.16–1.36, WL 2.44–3.00, PTH 0.96–1.20, PTL 0.48–0.52 (n=10). Entire body generally shiny except where obscured by dense pubescence; head, mesosoma, and petiole dark reddish-brown to dark brown; gaster darker brown; scape and legs brown. Head with fine, longitudinal striae covering much of the head in full-face view, striae beginning from frontal lobes and diverging toward posterior corners of head, fading at corners and sides; sides and underside of head lacking sculpture; dorsally with numerous, fine, appressed pubescence and scattered elongate, erect setae present. Pronotum with sub-circular, concentric striae that become longitudinal near rear margin; pubescence appressed, abundant; 5–8 elongate, erect setae present. Mesonotum and propodeum with deep transverse striae; propleuron, mesopleuron, and basalar lobe lacking sculpture; pubescence abundant dorsally, appressed. Metasternum lacking paired, elongate, spiniform processes between hind coxae. Petiole widest at base, gradually tapering apically to a short spine directed rearward; mostly lacking striae with only faint striae present near base; subpetiolar process rounded triangular; appressed pubescence present anteriorly and laterally, but mostly absent posteriorly. Gaster mostly shiny beneath pubescence, lacking striae or other strong sculpture, but with fine coriaceous sculpture (seen at high magnification); fine, appressed pubescence dense, spaces between hairs less than 1/3 the length of a hair, often overlapping one another; scattered erect, elongate setae present.
Male: HL 1.00–1.08, HW 1.24–1.34, SL 0.18–0.22, EL 0.68–0.76, EW 0.40–0.44, OL 0.24, OES 0.16, WL 2.52–2.76, PTH 0.72–0.88, PTL 0.46–0.54, FWL 5.10–5.65 (n=5). Head, mesosoma, and petiole generally shiny except where obscured by dense pubescence; head, meso- and metasoma, legs, scape and pedicel yellow to yellowish-brown, remainder of funiculus brown. Head and mesosoma with abundant fine, white pubescence except on anepisternum where pubescence is mostly absent. Eyes extremely large, maximum diameter of each eye at least 70% of the length of the head in full-face view. Ocelli large, the length of each ocellus wider than distance between lateral ocellus and eye margin; in full-face view, lateral ocelli protrude beyond posterior border of head. Mesosoma: pronotum lacking sculpture; mesoscutum with fine transversely arcuate striae anteriorly, striae becoming longitudinal posteriorly; mesoscutellum raised and convex, lacking sculpture; propodeum with weak to moderately strong transverse striae laterally, and especially posterodorsally; mesopleuron mostly lacking striae. Petiole bluntly rounded apically, with rounded triangular subpetiolar process anteriorly; densely pubescent anteriorly and laterally, but reduced pubescence posteriorly. Disc of abdominal sternum IX trapezoidal, breadth slightly greater than length; posterior lobe length approximately twice maximum lobe width, basal half narrowed. Telomeral apex broadly rounded; telomere length distinctly greater than height; valviceps ventral apex strongly produced, narrow; valviceps apical margin broadly concave; vertical portion of dorsolateral carina and lateral margin of subapical lamina meeting at an angle; apicodorsal lobe of valviceps broad; subapical lamina narrow.
Queen: No specimens measured, but similar to workers in color and general appearance except slightly larger, with mesosoma developed for wings.
Distribution (Fig. 26). USA. Alabama: Baldwin and Houston Counties. Florida: Alachua, Baker, Bay, Bradford, Broward, Citrus, Clay, Collier, Columbia, Dade, De Soto, Duval, Franklin, Gadsden, Gilchrist, Glades, Hamilton, Hendry, Hernando, Highlands, Hillsborough, Indian River, Jackson, Jefferson, Lake, Lee, Leon, Levy, Liberty, Madison, Marion, Martin, Monroe, Nassau, Okeechobee, Orange, Osceola, Palm Beach, Pasco, Polk, Putnam, Sarasota, St. Lucie, Sumter, Taylor, Volusia, Wakulla, and Walton Counties. Georgia: Chatham, Clinch, Dougherty, Glynn, Lowndes, and Ware Counties. Mississippi: Harrison County. According to Deyrup and Cover (2004), the occurrence of this species in the Caribbean region and Central and South America is unclear due to historical misidentifications and nomenclatural changes. Distributional information from Deyrup and Cover (2004) and examination of specimens from the ABS, MEM, UGA, USNM, and personal collections of Dan Suitor and Doug Booher.
Discussion. Odontomachus brunneus appears to be restricted to the southeastern US. Previous records of O. brunneus from the Caribbean, and Central and South America (Brown 1976) all appear to be of O. ruginodis. The situation was clarified by Deyrup et al. (1985) who recognized the distinction between O. ruginodis and O. brunneus and revived the former from synonymy with the latter. Brown’s statement (1976) that O. brunneus is well adapted to “marginal habitats is consistent with the ecology of O. ruginodis, whereas O. brunneus in the Southeast is generally found in undisturbed natural habitats.
In the US, O. brunneus occurs in a wide variety of natural habitats including flatwoods, mesic forests, pine savannas, swamp forests, oak-pine scrub, upland scrub, sandhills, bayheads, edges of seasonal ponds, and elevated tussocks. Nests of O. brunneus have been found in leaf litter, rotting logs, at tree bases, and in open to partially covered sandy areas. Nest architecture has been explored and discussed by Cerquera and Tschinkel (2010). Workers occasionally forage during the day, but are more active at night. Upon colony disturbance, workers are not aggressive, but instead quickly retreat or vacate the nest. This is in sharp contrast to the aggressive defensive stinging behavior of O. haematodus. Alates have been collected from May through December. This broad time frame for alate activity contrasts sharply with the early summer activity of O. haematodus.
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 526-529, DOI: 10.11646/zootaxa.3802.4.6, http://zenodo.org/record/249896