Pheidole senex

Gregg (1963) reports P. senex from Campo, Colorado, in short grass prairie nesting in clay under rocks at 1300 m. Cole recorded it in New Mexico from 2000 to 2700 m. At Springerville, Arizona, I found a colony under a rock in grassy desert. In the Texas Panhandle, Moody and Francke (1982) found two colonies, one beneath a stone and the other in open soil. (Wilson 2003)

Identification
The major of this species can be recognized by the very elongate, sharp lateral connules on the sides of the postpetiole. The anterior half of the head is covered with parallel rugae, the tops of the posterior lateral lobes are covered with fine rugae, the region between the sculptured areas is predominantly smooth and shining. Most surfaces of the minor worker are sculptured: the head has a mixture of parallel striae and punctures, and the entire mesosoma is punctate (usually part of the dorsum of the pronotum, and side of the pronotum are partially smooth and glossy).

Also see the description in the nomenclature section.

Distribution
West-central Arizona through New Mexico to the Texas Panhandle and southern Colorado; apparently rare. (Wilson 2003)

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

Nomenclature

 * anfracta. Pheidole pilifera subsp. anfracta Cole, 1952c: 278 (s.w.) U.S.A. Junior synonym of senex: Cole, 1953e: 298; Gregg, 1959: 30.
 *  senex. Pheidole senex Gregg, 1952a: 1 (s.w.) U.S.A. Senior synonym of anfracta: Cole, 1953e: 298; Gregg, 1959: 30. See also: Wilson, 2003: 596.

Description
From Wilson (2003): DIAGNOSIS A member of the “pilifera complex” of the larger pilifera group, comprising Pheidole calens, Pheidole californica, Pheidole carrolli, Pheidole cavigenis, Pheidole clementensis, Pheidole creightoni, Pheidole hoplitica, Pheidole littoralis, Pheidole micula, Pheidole pilifera, Pheidole polymorpha, Pheidole rugulosa, Pheidole senex, Pheidole soritis, Pheidole tepicana and Pheidole torosa, which complex is distinguished by the following traits. Major: dorsal head surface extensively sculptured; occipital lobes transversely rugulose (or, in carrolli smooth, in littoralis foveate, and in micula and soritis carinulate), postpetiole from above diamond-shaped, trapezoidal, or spinose. Minor: eye medium-sized to large.

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

Major: large; mesonotal convexity subangulate in dorsal-oblique view, and descends steeply to metathorax in side view; petiolar node tapers to a point in side view; postpetiole from above spinose; sides of pronotum, mesonotum, and propodeum, longitudinally carinulate; anterior dorsal profile of head flat; cephalic pilosity short and erect.

Minor: entire dorsal surface of head except mid-section of clypeus longitudinally carinulate; all of mesosoma foveolate and opaque.

MEASUREMENTS (mm) Paratype major: HW 1.74, HL 1.86, SL 0.78, EL 0.22, PW 0.82. Paratype minor: HW 0.64, HL 0.66, SL 0.68, EL 0.14, PW 0.40.

COLOR Major and minor: light yellowish to reddish brown.



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

Type Material
COLORADO: 14 km south of Campo, Baca Co., extreme southeastern Colorado, col. Robert E. Gregg., - as reported in Wilson (2003)

Etymology
L senex, old, senior, possibly alluding to rugulose sculpture of head and mesosoma. (Wilson 2003)