Pogonomyrmex bigbendensis

A rare species, it nests in the soil.

Identification
Key to North American Pogonomyrmex

Shows some similarities to Pogonomyrmex desertorum. It can be distinguished as the cephalic sculpture is almost absent and the head is mostly smooth and shining. (Mackay and Mackay 2002)

Distribution
Southern Texas and Chihuahua, Mexico.

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

Habitat
Creosotebush scrub.

Nomenclature

 *  bigbendensis. Pogonomyrmex (Pogonomyrmex) bigbendensis Francke & Merickel, 1982: 371, figs. 1, 2, 9, 12, 15 (w.) U.S.A.

Worker
Measurements of holotype followed, in parenthesis, by the ranges observed in paratypes: Head length 1.75 mm (1.49-1.75 mm), head width 1.85 mm (1.61-1.87 mm), cephalic index 105.7 (105.2-108.7), scape length 1.20 mm (1.08-1.22 mm), scape index 71.35 (71.35-73.78), maximum eye length 0.40 mm (0.34-0.41 mm), maximum eye width 0.28 mm (0.26-0.30 mm), ocular index 22.86 (22.82-23.26), Weber's length l.82 mm (l.56-1.85 mm), petiolar node length 0.48 mm (0.44-0.49 mm), maximum width of petiolar node 0.36 mm (0.30-0.40 mm), postpetiolar length 0.39 mm (0.35-0.40 mm), postpetiole width 0.51 mm (0.45-0.54 mm).

Head slightly broader than long; eye small, weakly convex, not extending beyond lateral margin of head. Mandible with five or six teeth: ultimate basal tooth distinctly offset from basal mandibular margin, forming a rounded angle; penultimate basal tooth greatly reduced or aborted; third basal tooth very broad basally, somewhat pointed apically, with lateral margins deeply excised; second basal tooth apparently aborted; first basal, subapical, and apical teeth broad basally, blunt apically. Apical margin of mandible broadly convex, basal margin somewhat sinuous. Antennal scape moderately curved on basal one-half, area of bend compressed. Base of antennal scape similar to that of P. bicolor Cole: with very narrow basal flange; superior and inferior lobes subequal; impression on lateral surface of basal enlargement small and shallow, the longitudinal peripheral carina very narrow and not ending in a distinct point. Lateral lobes of clypeus produced in front of antennal insertions, projecting anteriorly beyond level of median clypeal lobe; frontal lobes ascending moderately steeply from clypeal lobe, not forming a deep impression for median clypeal lobe and adjoining frontal triangle. Median cephalic rugae longitudinal, widely spaced, extremely fine; interrugal spaces strongly shiny; in lateral view rugae reduced to very indistinct striae, either parallel or somewhat concentric behind eyes. Posterior corner of head smooth and shiny.

Contour of thorax, petiole, and postpetiole, in lateral view. Dorsum of thorax flat, epinotal declivity short and distinct, epinotal armature absent. Thoracic rugae coarse, transverse and widely spaced on anterior of pronotum, transverse to longitudinal on posterior of pronotum; transverse and more closely set on mesonotum and epinotum; interrugal spaces strongly shiny on all segments. Dorsal portions of metasternal flanges fused, forming a single arcuate carina across posterior declivity of epinotum. Contours of petiolar and postpetiolar nodes, in dorsal view. Ventral peduncular process of petiole distinct, thick, rounded, with 0-5 erect hairs. Petiolar and postpetiolar nodes shagreened, rugae when present confined to posterior half; anterior declivity of petiolar node short, meeting peduncle in broad, well rounded angle. First gastric segment slightly broader than long. Body color medium to dark ferrugineous red.

Type Material
Type nest series (workers only) from Rio Grande Village (565 m), Big Bend National Park, Brewster Co., Texas, 30 July 1978 (J. V. Moody, O. F. Francke). Holotype worker deposited at the California Academy of Sciences, San Francisco.

Paratypes deposited in the following collections: California Academy of Sciences, American Museum of Natural History, Museum of Comparative Zoology, Los Angeles County Museum, and Texas Tech University.