Neivamyrmex texanus

This is a widespread ant, found in many different types of habitat. Although not commonly seen, N. texanus is a large (for Neivamyrmex) and conspicuous ant when it is actively foraging. Immigration columns are prominent and may often be seen from some distance away when crossing a suitable background. One observed near Tucson stretched well over 100 yards across the desert and could be readily seen as it meandered across the light colored sand. The blind snake, Leptotyphlops dulcius, was observed in the column. Occasionally, when an ant displayed an interest in the snake, it was quickly flicked off (pers. obs., GCS). Plsek et al. (1969) observed Helluomorphoides texanus (LeConte) in raiding columns of N. texanus and reported their observations on behavior of this species in the laboratory. (Snelling and Snelling 2007)

Identification
Snelling and Snelling (2007) - Small workers may be difficult to distinguish from those of Neivamyrmex nigrescens, but larger workers are fairly easy to distinguish with a little practice. Males may be readily recognized by the distinctive shape of the paramere.

Watkins (1972) - Worker: Petiole distinctly longer than broad; head, alitrunk, petiole and postpetiole densely granulated; basal and sloping surfaces of propodeum joining in an acute angle; occipital corners usually angular but not curved outwards. Queen: Eyes distinct; petiole rectangular, one and one-half times wider than long, with the anterior and dorsal surfaces (in profile) forming one continuous arc; posterodorsal corners of head rounded; head and alitrunk finely granulated; setae scattered over all body surfaces. Male: apex of stipes with a tall dorsal projection; ocelli small and widely separated from compound eyes; mandibles not sickle-shaped; head and alitrunk black, gaster rusty-brown.

Worker Variation. Length 2.5-5.1 mm. Occipital corners usually triangular, but are somewhat rounded in specimens studied from Black Mts., North Carolina. Basal tooth of mandible varies from moderately large to indistinct. Basal and sloping surfaces of propodeum usually form a distinct corner at their juncture, but a few specimens have more rounded propodea, especially those studied from Colorado Springs, Colorado, and Las Vegas, New Mexico. Queens: (Two specimens examined). Length (nonphysogastric, head deflected) 9.5-10.8 mm. Head length 1.4-1.6 mm, width 1.55-1.7 mm. Dorsal surface of promesonotum may or may not have a shallow concavity. Mesopropodeal suture broad and shallow or incomplete dorsally. Petiole 1.5-1.6 times wider than long. Males: Length (head deflected) 11-13 mm. Dorsal projection of stipes usually angular, but the projections are truncated in three males studied from Waywick, Virginia. Setae usually long, semierect, and thickly distributed over the body, but are short, sparse, and appressed on a few specimens. Borgmeier (1955), in his key to nigrescens (=texanus) indicated that the terminal branch of the radial wing vein is shorter than the branch to the stigma; however, I found this highly variable-sometimes the terminal branch is longer, sometimes the branch to the stigma is longer, and sometimes the two branches are about equal in length. The length of the second submarginal (cubital) wing cell varies from 2.4 to 3.2 times longer than wide. Wings vary from slightly to strongly infuscated. One male from Brown Canyon, Baboquivari Mts., Arizona, (LACM) is very atypical and could be the undescribed male of Neivamyrmex rugulosus. It is unusually small (length 10.2 mm), with a darker gaster (blackish instead of rusty-brown as in all other specimens of this species examined), with more transparent wings, and truncated dorsal projection of the stipes.

Distribution
USA: AZ east to FL, north to CO, VA; MEXICO: Chihuahua, Hidalgo, Jalisco, San Luis Potosi.

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

Biology
In Tamaulipas, Mexico, Neivamyrmex texanus was observed raiding a colony of (Rabeling & Sanchez-Peña, unpublished data). In the mountains of southern Arizona, two army ant species, Neivamyrmex nigrescens and Neivamyrmex rugulosus, prey on Trachymyrmex arizonensis (Miranda et al. 1980, LaPolla et al. 2002). Based on these few observations, army ants seem to be important predators of at least some Trachymyrmex species, and their raids may result in a significant brood loss and partial destruction of the fungus garden (LaPolla et al. 2002).

Nomenclature

 *  texanus. Neivamyrmex texanus Watkins, 1972: 353, figs. 2-4, 11, 14, 17-19, 33, 34, 49, 61 (w.q.m.) U.S.A. Wheeler, G.C. & Wheeler, J. 1984: 273 (l.); Taber & Cokendolpher, 1988: 95 (k.). See also: Ward, 1999a: 88; Snelling, G.C. & Snelling, R.R., 2007: 491.

Type Material
Holotype male, length 12.2 mm, red label, collected by W. M. Wheeler, Austin, Texas, U.S. A. (“10-13-00,” date on one paratype only) deposited in MCZ. Paratypes, red labels, deposited as follows: 1 ; 1 ; 1 ; 2, including 1 with two workers on the same pin.

Worker
Major. (Waco, Texas, colony W-58). Length 5.1 mm. Head approximately as long as wide, slightly narrowed posteriorly; median length without mandibles 1.20 mm; greatest width 1.25 mm; sides slightly convex; occipital corners triangular, but not curved outwards. Eyes with distinct corneas. Mandible triangular; weakly striated; with a moderately large basal tooth, and with the basal margin curving into the masticatory margin which has three or more small blunt teeth. Antennal fossa with a very weak ridge in front, but with a sharply defined lateral border. Scape widened apically; extending above eye level; length 0.9 mm. Flagellum gradually thickened; length 2.0 mm; segments 3 and 4 approximately as wide as long, 5-10 longer than wide; apical segment two and one-half times longer than wide. Alitrunk length 2.1 mm; greatest width 0.8 mm. Pronotum with a prominent transverse ridge on anterior margin, and a continuous groove near the ventrolateral and posterolateral margins. Promesonotum, in profile, moderately convex. Mesopropodeal indentation strongly impressed. Propodeum with a slightly convex basal surface, and somewhat concave descending surface, which form a distinct corner at their juncture. Petiole longer than wide, rectangular, with parallel sides; length 0.6 mm; width 0.4 mm; height 0.45 mm; slightly convex dorsally and more slanted anteriorly; anteroventral projection weak and often covered by the metacoxa. Postpetiole slightly trapezoidal viewed from above, narrowed anteriorly; length 0.45 mm; greatest width 0.5 mm; height 0.5 mm; slightly convex dorsally. Gaster oval and more narrowed posteriorly; length 1.7 mm; greatest width 1.15 mm; greatest height 1.05 mm. Length of metafemur 1.6 mm, metatibia 1.5 mm. Proximal tarsal segment longer than segments 2-4 combined, segment 4 shortest. Claws without teeth. Head, alitrunk, petiole, and postpetiole thickly granulated and weakly rugate dorsally. Gaster smooth. Setae erect, unequal in length, moderately abundant on all body surfaces. Color dark reddish-brown to blackish-brown, gaster and legs lighter.

Queen
(Waco, Texas, colony W-157). Nonphysogastric. Length (head in hypognathous position) 10.8 mm. Head slightly wider than long with a broad median impression; median length 1.4 mm; greatest width 1.55 mm; sides slightly convex; occipital corners rounded; occipital margin broadly concave. Eyes with distinct convex corneas, located on upper one-third of head. Mandible moderately narrow, slightly thickened about one-third length from base, and gradually tapering apically, with a weakly concave cutting margin. Frontal carinae rounded, with a deep median impression between them, and not extending below antenna! fossae. Scape gradually thickened distally, reaching lower eye margin; length 0.9 mm. Flagellum not apically thickened; segment 1 short, 2-10 about equal in diameter, 2 and 3 as wide as long, 4-10 slightly longer than wide; apical segment almost 3 times longer than wide, and two times longer than anteapical segment. Alitrunk length 3.1 mm; greatest width 1.3 mm at the propodeum; gradually widened posteriorly; without a median longitudinal impression, but with a shallow dorsal concavity on the propodeum. Anterior border of pronotum upturned. Promesonotal suture distinct. Mesopropodeal suture broad and shallow on dorsum. Pronotum with small, but distinct, posterior dorsolateral projections. Promesonotum, in profile, convex and more strongly sloping anteriorly. Propodeum, in profile, almost flat dorsally and slightly rising posteriorly, with dorsal and sloping surfaces broadly rounded at their juncture. Petiole transverse, one and one-half times wider and taller than long; length 0.7 mm; width 1.05 mm; height (including ventral projection) 1.1 mm; dorsal surface with a deep, broad, longitudinal concavity; anterior border, viewed dorsally, almost straight with broadly rounded corners; sides parallel; posterior border slightly concave; anterior and dorsal surfaces, in profile, forming a continuous arc; posterior surface slightly concave; anteroventral projection semicircular. Gaster elongate; length 6.2 mm; greatest width 2.4 mm; greatest height 2.0 mm; apical segment strongly tapering with a deep triangular notch in apex of fifth gastric sternite. Length of metafemur 1.6 mm, metatibia 1.5 mm. Proximal tarsal segment two times longer than segment 2, segment 4 shortest. Claws without teeth. Head, alitrunk and petiole finely granulated, and with abundant short, erect setae. Gaster smooth, except for scattered punctations bearing short, appressed setae. Color reddish brown.

Male
(Austin, Texas). Thoroughly described as Eciton schmitti by Wheeler and Long (1901:161), and as Neivamyrmex nigrescens by Borgmeier ( 1955:496).

References based on Global Ant Biodiversity Informatics

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