Pheidole rugulosa

Stefan Cover (unpublished collection notes) found numerous colonies of rugulosa in the deserts of southern Arizona and southwestern New Mexico at 1300–1700 m, in xeric habitats ranging from grazed grassland desert to rabbitbrush-mesquite desert, mesquite-acacia dominated wash, and riverbank desert scrub. The ants usually nest in the open soil, with the entrances surrounded by either crescentic or full craters; the entrance of one nest was in a grass clump. Similar nest site preferences are reported from western Texas by Moody and Francke (1982). According to Cover, colonies may consist of several hundred individuals or more, and, unusually for Pheidole, are at least sometimes polygynous. Seeds are occasionally found in the nests. (Wilson 2003)

Identification
The majors of this species are small (total length about 2.5 mm, head length 1.2 mm). The anterior 1/2 of the head is longitudinally striate, the posterior half of the head is predominantly smooth and shining, the tops of the lobes have transverse striae, which extend onto the fronts of the lobes, as well as extend longitudinally on the posterior surfaces of lobes. The humeral angles are present, but are not notably developed; the connules are poorly developed. The minors are small, dark brown specimens, with a shiny head, shiny pronotum, the remainder of the mesosoma is punctate. (Mackay and Mackay 2002)

Also see the description in the nomenclature section.

Key to the Pheidole of the United States

Distribution
Texas, New Mexico, Arizona. (Wilson 2003)

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

Biology
Mackay and Mackay (2002) - These ants make small nests in the soil, with the nest entrance usually surrounded by a small mound. This species is very common near Las Cruces, but was not found in other sites in New Mexico. The nests and the specimens are small, making them easily overlooked.

Nomenclature

 *  rugulosa. Pheidole rugulosa Gregg, 1959: 26 (s.w.q.m.) U.S.A. See also: Wilson, 2003: 595.

Description
From Wilson (2003): DIAGNOSIS A member of the “pilifera complex” of the larger pilifera group; for a characterization of the complex, see under Pheidole pilifera.

P. rugulosa is distinguished within the complex by the following combination of traits.

Major: rugulae on occiput seen in full-face view limited to a narrow strip; longitudinal carinulae originating on the frontal triangle travel all the way to meet the occipital rugulae, but other cephalic carinulae do not reach beyond the midpoint of the head capsule; anterior strip of the pronotum transversely carinulate; mesonotal convexity very low; postpetiole seen from above laterally angulate.

Minor: exceptionally large, forward-placed eyes; mesonotal convexity present in dorsal-oblique view; propodeal spines well developed.

Throughout much of southern New Mexico and Arizona, P. rugulosa occurs with Pheidole soritis, with which it is easily confused. P. rugulosa is most easily distinguished from that species by the major’s well-developed humeral angles, which are inconspicuous and rounded in soritis, and the large shiny areas on the posterior dorsal surface of the head, which is variably sculptured in soritis.

MEASUREMENTS (mm) Paratype major: HW 1.04, HL 1.12, SL 0.54, EL 0.22, PW 0.56. Paratype minor: HW 0.52, HL 0.52, SL 0.42, EL 0.14, PW 0.44.

COLOR Major: reddish to medium brown, gaster often somewhat darker. Minor: medium to dark brown, even blackish.



'''Figure. Upper: paratype, major. Lower: paratype, minor. Scale bars = 1 mm.'''

Type Material
ARIZONA: Tucson, - as reported in Wilson (2003)

Etymology
L rugulosa, a small amount of wrinkling, evidently referring to the occipital rugulation. (Wilson 2003)