Temnothorax obliquicanthus

Mackay (2000) "One nest was in an exposed area surmounted by a 10-cm crater (Wheeler and Wheeler. 1986). One nest in New Mexico was in the soil together with Pheidole sp. Nests are monogynous (Frumhoff and Ward. 1992).The large eyes may be connected with the diurnal habitats of the ants in open areas. where the workers could scan the surrounding area before exiting the nest (Gregg. 1953)."

Identification
Mackay (2000) - A member of the Temnothorax tricarinatus species complex. The worker of this species is easily recognized due to the large, kidney shaped eye. In addition, nearly all surfaces are densely and coarsely punctate. The entire first tergum is punctate, but the punctures are fine and difficult to see unless the light is placed to reflect from the surface. The antenna has 12 segments.

This species is easily recognized and separated from all other known North America Temnothorax by the large, oblong eyes. It could only be confused with Temnothorax liebi, which is pale yellow, with black eyes and has a completely smooth first tergum of the gaster. The sculpturing of the gaster would serve to further confirm the identity of this species. This species was independently discovered by Gregg (1953), but Cole described it first.

Distribution
US - Nevada, Colorado, New Mexico, and Texas. Mexico - Baja California.

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

Habitat
Mackay (2000) "Found in dry grassy areas to semi-moist meadows and to sagebrush or highly disturbed areas and high, dry short-grass plains above a river valley."

Abundance
Rarely collected.

Biology
Gregg (1953) "The specimens of obliquicanthus which I collected came from Higbee, Colorado, in the southeast part of the state, twenty miles south of La Junta. They were obtained from two general habitat types, semi-moist meadow near the Purgatoire River, and high dry, short grass plains above the river valley. The approximate elevations of these sites are 4400 ft. and 4500 ft. respectively. Dr. Cole's specimens were taken twelve miles south of Santa Fe, New Mexico, in a grassy area."

Castes
Known only from the worker caste.

Nomenclature

 *  obliquicanthus. Leptothorax (Myrafant) obliquicanthus Cole, 1953c: 28, figs. 1, 2 (w.) U.S.A. See also: Mackay, 2000: 380.

Worker
Holotype, worker (Cole coll. no. N-279). Length, 2.6 mm. Head rather large, excluding the mandibles a little longer than broad, narrow in front than behind, the occipital corners broadly rounded, the sides feebly convex. Eyes very large much elongated, subobovate and sub reniform, convex, oblique, and directed anterio-ventrad, the dorsal portion broader than the ventral, the distance between the lower margin and the mandibular insertion equivalent to less than one-half greatest transverse diameter of the eye. Mandibles with 5 distinct teeth. Clypeus moderately convex, with broadly rounded anterior border. Frontal area indistinct. Antennae 12-segmented; scapes rather robust, not extending to the occipital margin; first funicular segment as long as the succeeding three segments taken together, the distal segment of the club of about the same length as the preceding two segments taken together.

Thorax rather robust; pronotum convex, with rounded humeral angles; dorsum of meso- and epinotum flat in profile, the mesoepinotal suture obsolete; sides of meso- and epinotum strongly compressed laterally; epinotal spines robust, broad at base, distinctly tapered from base to the rather blunt apex, about as long as the distance between their bases, very slightly curved, directed upward, backward, and outward. Petiole, when viewed in profile with the anterior face flat and sloping sharply anaterioventrally, the apex of the node subtruncated, only feebly convex, and sloping steeply posterioventrally; when viewed from above the node is transversely subrectangular; peduncle very short, ventral surface with a prominent, triangular tooth. Postpetiole much broader than the petiole, but not twice as broad, its dorsal surface very convex, when viewed from above it is transversely subrectangular. Legs stout, femora incrassated.

Gaster ovoid, truncate basally, the basal angles sharp.

Thorax, petiole, and postpetiole opaque; head subopaque. Head finely and longitudinally rugulose-reticulate and finely punctate; mandibles longitudinally striated; clypeus coarsely and longitudinally rugulose. Thorax, petiole, and postpetiole more coarsely rugulose-reticulate and with abundant, larger, and more pronounced punctures; pleurae with rather coarse longitudinal rugae. Gaster and legs shining, very finely coriaceo-reticulate.

Hairs silvery; short, rather numerous, blunt, subclavate, and erect, as well as some which are short, slender, pointed, appressed and subappressed, on head; longer, slender, and sharper on clypeal border, gula, and mandibles; longer and more clavate on dorsum of thorax, petiole, and postpetiole; erect on thoracic dorsum, reclinate on petiole, postpetiole, and gaster.

Color of body black, appearing as very dark brown under high magnification; leg articulations and apical half of mandibles brown.

Type Material
The holotype and a series of 61 paratype workers were collected by the writer on August 10, 1951, at a point 12 miles south of Santa Fe, New Mexico, along U. S. highway 85. The ants were ambling about on the soil of a dry, grassy area and were apparently foraging. The nest was not found.

Mackay (2000) - Holotype in Cole collection, paratypes in Cole collection and, , [seen].

References based on Global Ant Biodiversity Informatics

 * Bestelmeyer B. T., and J. A. Wiens. 2001. Local and regional-scale responses of ant diversity to a semiarid biome transition. Ecography 24: 381-392.
 * Cover S. P., and R. A. Johnson. 20011. Checklist of Arizona Ants. Downloaded on January 7th at http://www.asu.edu/clas/sirgtools/AZants-2011%20updatev2.pdf
 * Dattilo W. et al. 2019. MEXICO ANTS: incidence and abundance along the Nearctic-Neotropical interface. Ecology https://doi.org/10.1002/ecy.2944
 * Johnson, R.A. and P.S. Ward. 2002. Biogeography and endemism of ants (Hymenoptera: Formicidae) in Baja California, Mexico: a first overview. Journal of Biogeography 29:10091026/
 * Mackay W. P. 2000. A review of the New World ants of the subgenus Myrafant, (genus Leptothorax) (Hymenoptera: Formicidae). Sociobiology 36: 265-444.
 * Mackay W. P., and E. E. Mackay. 2002. The ants of New Mexico (Hymenoptera: Formicidae). Lewiston, New York: Edwin Mellen Press, 400 pp.
 * Mackay, W., D. Lowrie, A. Fisher, E. Mackay, F. Barnes and D. Lowrie. 1988. The ants of Los Alamos County, New Mexico (Hymenoptera: Formicidae). pages 79-131 in J.C. Trager, editor, Advances in Myrmecololgy.
 * Mackay, W.P. and E. *Mackay, W. P. and E. Mackay. 2002. The ants of New Mexico (Hymenoptera: Formicidae). Edwin Mellen Press, Lewiston, NY.
 * O'Keefe S. T., J. L. Cook, T. Dudek, D. F. Wunneburger, M. D. Guzman, R. N. Coulson, and S. B. Vinson. 2000. The Distribution of Texas Ants. The Southwestern Entomologist 22: 1-92.
 * Vásquez-Bolaños M. 2011. Lista de especies de hormigas (Hymenoptera: Formicidae) para México. Dugesiana 18: 95-133
 * Wheeler G. C., and J. Wheeler. 1986. The ants of Nevada. Los Angeles: Natural History Museum of Los Angeles County, vii + 138 pp.