Pheidole pilifera

Colonies of pilifera excavate crater nests in exposed soil and harvest seeds, which are stored in nest chambers. In Colorado, Gregg (1963) found the species (as “subsp. coloradensis”) abundant at 1500 to 2600 m, in a wide range of habitats, from short-grass prairie, roadsides, and herbaceous semi-desert to mixed canyon forest and mountain mahogany shrub. Sexuals were present in the nest from the first week in June to the last week in July. P. pilifera is also notable in Colorado as the host of the social parasite Pheidole inquilina. In Nevada, pilifera ranges between 900 and 2300 m, nesting in desert and juniper-pinyon woodland, both under stones and in the open soil, where it forms craters 25–60 mm wide (G. C. and J. Wheeler 1986g). According to Stefan Cover (personal communication), “In the eastern U. S. pilifera occurs in open, grassy habitats, especially those with sandy soils containing a little clay. It is less common in pure sand, thus in pine barrens. Mating flights occur in early to mid July. Colonies are monogynous, and the newly mated queens start colonies singly. Minors are ‘shy’ foragers but recruit to good food sources. Majors seldom leave the nest except when recruited. Their primary function is to block nest passages, which they do effectively.” (Wilson 2003)

Identification
See the description in the nomenclature section.

Distribution
Pheidole pilifera is the most widespread and northward-reaching of all the Nearctic Pheidole. The species, as presently broadly construed, ranges from Massachusetts south to Georgia and west to California, extending through the midwest as far north as Minnesota, North Dakota and southwest to Utah, New Mexico, and Arizona. (Wilson 2003)

Distribution
This taxon was described from the United States.

Description
From Wilson (2003): 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 characterized by the following traits. Major: dorsal head surface extensively sculptured; occipital lobe horizontally 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. pilifera is distinguished within its complex by the following combination of traits.

Major: relatively large, HW about 1.6 mm; posterior dorsal profile of head straight or slightly concave; mesonotal convexity prominent and symmetrical in side view; propodeal spines robust, long, and nearly vertical to basal propodeal face; petiolar node in side view tapering apically to a blunt point; postpetiolar node from above very broad relative to petiolar node, and bluntly spinose.

Minor: eyes medium-sized; humerus in dorsal-oblique view subangulate; all of head posterior to the clypeus and mesosoma foveolate and opaque.

Closely related to Pheidole carrolli but very different in sculpturing of the major.

My synonymy of artemisia, coloradensis, and pacifica follows Creighton (1950a) in placing them as geographic variants, or subspecies, and thence here into synonymy at the species level. However, this assignment is not well documented and thus is regarded as provisional. The pattern of geographic variation within pilifera is as follows.

Western populations (“coloradensis”) ranging from North Dakota and Colorado to Nevada display a narrowing of the transverse rugulose band to the rearmost part of the major occiput and loss of the longitudinal carinulae on the vertex (anterior to the occiput), an area that is spotted with coarse foveae and shiny interspaces. The trend is climaxed in Nevada and California (“pacifica”) by replacement of the foveae on the vertex of the major by fine punctures. Southwestward, in Utah and Arizona (“artemisia”), the broad band of occipital rugulae of the major in eastern populations (“typical” pilifera) is retained, but the carinulae of the vertex are lost and replaced by a shiny surface.

MEASUREMENTS (mm) Major (Haddam, Connecticut): HW 1.60, HL 1.72, SL 0.74, EL 0.24, PW 0.68. Minor (Haddam): HW 0.54, HL 0.60, SL 0.52, EL 0.12, PW 0.36.

COLOR Major: light reddish brown.

Minor: medium reddish brown.



'''Figure. Upper: major. Lower: minor. CONNECTICUT: East Haddam. Scale bars = 1 mm.'''

Type Material
Mus. Naturkunde Humboldt-Univ. Berlin. - as reported in Wilson (2003)

Etymology
Gr pilifera, hairy. (Wilson 2003)